Frequently Asked Questions/Tech Topics
(See Photos Below)
Can I put W7, W8, or W9 heads on my factory
340/360 block or 59 degree R3 block?
What does a "Siamese bore" block
mean, and how do I know if my block is Siamese or not?
How far can I safely bore my
How do I identify a specific MP race
What are the differences between
W7, W8, and W9 heads, and which one is "best"?
Mopar Performance Race Block, Frequent Machining
Using Cometic Head Gaskets
Can I put W7, W8, or W9 heads
on my factory 340/360 block or 59 degree R3 block?
is probably becoming my most frequently asked question lately, since the
marketplace seems to be flooded with W7/8/9 cylinder heads with MP
discontinuing some of the W9s and a lot of used CNC ported heads
popping up around the country.
The simple answer is YES. But as we all know, nothing when dealing with
Small Block Mopars can be simple. This is going to be a complicated
long, drawn out answer, but hopefully you will be able to follow along
and I won't have to re-type this on a daily basis.
Let's begin with factory 340/360 blocks as the R3 is a slightly
different animal in a few key areas. Any W7/8/9 head will bolt directly
to a 10 bolt factory block. They all utilize the standard factory 10
bolt location. However some people get confused because they hear that
many W7/8/9s have 18 head bolt holes. MOST do (but not all, some early
W7s are 10 bolt only) Those extra 8 head bolt holes do NOT have to be
utilized, you can just run the standard 10. However you will need to
utilize a specific W7/8/9 longer head stud kit. Your basic factory, or
W2/5 head stud kit won't work. As far as head gaskets go, just run your
standard 10 bolt, Fel Pro #1008 composite or Cometic 10 bolt LA style
Multi Layer Steel head gasket.
So bolting the heads to the block was not overly difficult. The next
major obstacle becomes pushrod clearance. The W7/8/9 style heads
generally have a much wider intake port runner tract than more normal
59 degree style heads. Generally, with a standard non offset lifter and
a standard W7/8/9 rocker arm, you will have pushrod to intake runner
wall interference. Certain rocker arms make this interference worse than
others. Most Jesel brand rockers for instance will have less offset on
the intake rocker than T&D rockers. Obviously the less offset, the more
interference with the runner wall. As a general rule of thumb, standard
off the shelf T&D rocker arms for W7/8/9 heads will have .550" offset
on the intake rocker. All the ones sold through Mopar Performance have
.550" offset. Now, T&D will custom make you any offset between .550" and
.725", so if ordering new, you can get more offset. Jesel will also
build custom rockers with increased offset, however most customers to
save money want to use existing rockers that are floating around for
sale, and most of these are not wild offset rockers. On everything I
have tested to date, a .550" offset intake rocker WILL clear the inner
runner wall on any CNC W7/8/9 head with a non offset lifter, but it is
VERY close. The outer runner wall has to be notched VERY carefully by
hand for clearance, and a 5/16" pushrod is all that will fit. A 3/8"
pushrod will break through into the inner runner wall on most heads, and
will require an epoxy fix.
To make the situation better, you can use an offset intake lifter. The
problem here is that most lifter companies do not cater well to the
Mopar crowd when it comes to offset lifters. In fact to the best of my
knowledge, no Hydraulic or Flat tappet lifters exist in .904" Chrysler
diameter. A couple companies offer an offset Solid Roller lifter, and
generally speaking, when you are thinking of running a W7/8/9 head, you
are probably already thinking of running a roller anyhow. One of the
problems I ran into was the fact that the Comp Cams #892 "Super Roller"
lifters don't fit 59 degree blocks? No way, no how. The rivet design on
them will not clear the lifter valley area, even with intense grinding.
You will most likely hit the water jacket if you try to make these
rivets clear. The lifter I am currently recommending that everyone use
is a Crane .903" Chevy Solid Roller lifter with a .210" intake offset
pushrod cup, and then have Crane install Chrysler "V" Link bars on them.
In a factory block, these will allow a 3/8" pushrod to be used. If you
want to use a Hydraulic or Flat tappet cam, then I am recommending just
use the standard non offset AMC style lifters, and a 5/16" Heavy wall
pushrod like a Smith Brothers .080" wall Chrome Moly unit.
Now to make matters worse, W7/8/9 heads do not oil the rockers through
the heads, like you are used to on LA style heads. W7/8/9s use pushrod
oiling with individual mount rocker arms that are mounted to a large one
piece rocker stand in pairs of rockers. The only other option to oil
these types of rocker arms is to have spray bars TIG welded in your
valve covers and spray bar oil the rockers. This works well with Jesel
type rocker arms that spray the rocker arms as it is for oiling, but
T&D rockers, which are a fully pressurized rocker body, need
modifications to be spray bar oiled. My personal recommendation is to
use spray bar oiling as a last resort. Pushrod oiling is the preferred
method to oil W7/8/9 rocker arms.
Pushrod oiling rocker arms on a stock factory 59 degree LA engine
block can get tricky. If you are using AMC style Hydraulic or Flat
tappet lifters, it will work OK. Basically all you are doing is putting
on a head/rocker combo that pushrod oils like a Magnum head conversion.
The problem comes when you start running large lift solid roller
camshafts. You can drop a solid roller lifter right in your factory LA
block, and it will get some oil to the top end, but the engine generally
will have excessively low oil pressure, and bearing damage will be
imminent. There are two ways around this. One is to have your lifter
bores bushed, with bronze bushings and run a small .035" oil feed hole
in the bushings. The bushings job is basically to act as an oil
restrictor, to restrict the amount of oil that is being bled off around
the lifter. Also another thing you run into on factory blocks more so
than on R3 race blocks, is that the lifter bores have 100,000+ miles on
them in most cases, and the bores are usually not located properly in
regards to angularity. So bushing the lifter bores corrects both of
these problems. The downside? Cost. Having your factory lifter bores
bushed is generally a $450-$600 machining operation, depending on the
shop doing the work, and not every shop owns the proper BHJ fixture for
bushing Small Block Chrysler lifter bores. However there is a second and
less expensive way out of this predicament. You can install copper
tubes in both the lifter oil galleys. Both passenger side AND drivers
side. Then you can drill your .035" oil feed holes in the copper tube in
each lifter bore, and the tube is what acts as your oil restrictor.
Mopar Performance has sold the lifter bore tube and peen package for
more than 20 years to block off all oil to the lifter bores. We are just
putting a new twist on this old idea. With the tubes installed, your oil
pressure will be back up to normal levels and your bearings will thank
you for it.
As far as R, R1, R1A, R2, and R3 race blocks are concerned, the only
differences that you need to be aware of, is the fact that the inner row
of extra head bolts, and their bosses will need to be HEAVILY
milled/ground off for link bar clearance on a solid roller lifter
application. This is a time consuming and tedious task, that has to be
done VERY carefully or you will break into the water jacket. Also, even
the R3 block will still require you to either bush the lifter bores or
tube the galleys to restrict the oil to the roller lifters, there is no
way around this. The oil feed holes in the lifter bores are just too
large out of the crate.
And there you have it, those are the basics of installing a W7/8/9
cylinder head on a 59 degree engine block. Now for the part most people
don't think about/know about. MOST W7/8/9 heads have 15 degree valve
angles. Stock LA heads utilize an 18 degree valve angle. This creates
obvious problems when trying to just bolt a W7/8/9 on a standard 18
degree shortblock/piston combo. There is no easy way around this other
than just having Custom 15 degree relief pistons made. Besides the fact,
that W7/8/9s have wider valve spacing than most LA heads, and they
usually utilize larger diameter valves as well. All of these factors
necessitate that custom pistons be used under a W/7/8/9 head. The good
news is, that with today's CNC technology, Custom pistons are not nearly
as expensive as they were only 10 years ago. Today, most piston
companies will do a fully custom piston combo for around $150-$200
extra. Well worth the cost, when you consider the added power gain of
using a large "W" series cylinder head. For more info, and differences
of W7/8/9 heads see the W7/8/9 section of the FAQs.
What does a "Siamese bore" block mean, and how do I know if my
block is Siamese or not?
First, let me state that the ONLY Small Block
Chrysler engine blocks ever cast that were Siamese bore, are R2/R3/R4/R5
Factory 273/318/340/360, T/A, X blocks, R blocks, R1, and R1As, were
never available in Siamese bore. So if you have anything other than an
R2/R3/4/5 you don't have Siamese bores.
Simply put, the Siamese bore blocks have the cylinder walls
"Siamesed" or "adjoined" together in between the cylinders. There is no
air gap for water to pass through between the cylinder bores. This
added material built up between the bores allow the cylinder walls to be
enlarged to much larger bore diameters before the wall thickness becomes
too thin to safely operate. (NOTE: See Photo #3) For instance a non
Siamese block at 4.125" bore may only have .120" of iron left on the
non-thrust sides of the cylinder walls. This would be getting close to
the maximum bore you can safely run on a block that will be making
significant power. Now in a Siamese bore block, at 4.125" bore we may
have .300+" of iron before we hit the opposite cylinder, which obviously
leaves room to run a much larger bore.
Simple way to check if your R3 is Siamese bore or not? Look up the part #
in the Mopar Performance catalog. But not everyone knows their part #
sometimes (We'll get to that in a different FAQ) So, easy way to tell is
just pop out a freeze plug on the sides of the block, and just look and
see if the two cylinder walls that you see have air space between them,
or if they are Siamesed together, and have a mass of cast iron between
far can I safely bore my block?
I'm often stumped why
people ask this question, because unless I have ESP or some other
psychic ability, I can not answer this question definitively. SONIC
testing is the only definitive way to know what your specific blocks
cylinder walls look like thickness wise. HOWEVER, I will give you some
generalities, just because so many people want to know. Do not take the
following as gospel - only the sonic tester knows for sure.
318 blocks don't like large bores PERIOD. .030" over is about the maximum
I will go before sonic testing a 318 block.
340 blocks: any year, 1967-1973, 4.04" is stock bore, and .030" over is
generally very safe. .040" over I would have no qualms generally doing.
Going .060" over to a 4.10" bore on a factory 340 block IMO is pushing
it, and I would only do this knowing my sonic #s. Largest known running
340 block that I know of is at 4.125" bore.
360 blocks: and here we get into certain years being felt to be better
than others. Generally yes, any 360 block up until 1974ish is considered
a little better block. And the above rules for a 340 apply. 1975 and
later, I will go .040" over with no qualms. I have also seen many blocks
from the late 70s go 4.07" or more and be used as successful race
blocks for many years. However, I'd sonic test the newer stuff if going
much over .040".
X block, R block, R1, R1As: These are all non Siamese bore. MP
recommends a max overbore of 4.08" on these blocks, however most people
find that this is erring on the side of caution. Many of these blocks
can go 4.10", 4.125" or even larger bore on occasion. My personal
feeling is anything over 4.10" on these and we sonic test. Up to 4.10" I
would not generally do it. Largest running non Siamese bore X, R, R1,
R1A, or R2 I know of would be 4.155"
Non Siamese R2/R3s, the above rules apply. Largest running non Siamese
bore R3 I know of, is at 4.165"
Siamese Bore R2/R3 race blocks: 4.180" is a common bore size to run on
these blocks, and many will run 4.22" as well. I personally would run up
to 4.22" without sonic testing. Over 4.22" and I would sonic test.
Largest bore running R3 engine that I personally know of, is at 4.25"
do I identify a specific MP race block?
This is probably #2 FAQ I get asked on almost a daily
basis. I'm going to start out with X blocks and work our way up through
X block is simple to identify, they have a large "X" cast into the
passengers side front of the block to the left of the timing cover,
behind where the alternator would sit on a factory engine setup. It is
plain as day and you can not miss it. If you've got a block with a Large
"X" here, it's an "X" block. Pretty simple. (NOTE: See Photo #1) MOST X
blocks were 318/340 main, but a little known factoid is that a SMALL #
of 360 main X blocks were produced. The lifter valley in an X block,
closely resembles a factory production block. The majority of its
strength was gained in the increased deck thickness and the main
webbing/pan rail areas. The bores are generally also a bit thicker in
all directions VS: a factory block. All "X" blocks are 59 degree lifter
R block: Again, where you would see an "X" on an "X" block, these have a
Large "R" cast in. (NOTE: See Photo #7) The "R" block was the successor to
the "X" block. It was available in 59* and 48* lifter bank angles. The
main benefit to the "R" block was the addition of availability of 48
degree heads, and the lifter valley area was greatly strengthened. All "R"
blocks have 10 head bolt pattern. Some EARLY "R" blocks did not have the
"R" designation, but yet had the traditional "R" series large lifter
bosses, and 48 degree bank angle. These were generally pre-production
R1 block: These have a large "R1" logo on the passenger side front of the
block. The biggest change in the R1 series was the addition of 18 head
bolt bosses for use with the 48 degree large "W" series 7/8/9 heads.
Both 59 degree and 48 degree versions available.
R1A block: Large "R1A" logo, again on the passenger side front of the
block. (NOTE See Photo #4)These are 18 bolt blocks, with a cut out
inner lifter valley that looks much like a factory block. (NOTE: See
Photo #2) Both 59 degree and 48 degree versions available.
R2 block: Large "R2" logo on passenger side front of the block. "R2" still
maintained a traditional wet sump lifter valley cutout. Available in
59* and 48* versions. "R2" are probably the rarest of all race blocks,
they were only available for a short time.
R3 block: Large "R3" logo on the front passenger side of the block. Biggest
change in "R3" blocks was the availability of Siamese bores, and the
valley on an "R3" has been completely filled in with iron, to make running
a dry sump application much easier on the engine builder. R3s were
available in the widest range of configurations, including 360 mains,
both 59* and 48* versions, and deck heights varying from 9.025" to 9.56"
R3s are the most common of the "R" Series blocks that you will run into
at swap meets etc.
Now that we have the basic generations covered, I'll go through to how
to ID exactly what version of a particular generation you may have run
First off let's get the whole 48 Degree VS: 59 Degree thing out of the
way. This is very easy to Identify, even for a novice. 59 degree lifter
bores are always down close to the edge of the lifter valley. (NOTE: See
Photo #6) That is a 59* R3 block. The 48* lifter bores are raised much
higher on the lifter bosses and are much closer toward the cam tunnel.
(NOTE See Photo # 2) That is a 48* R1A block. Also if you pay attention
in Photo #2, I noted how the intake lifter bores are also moved side to
side to accommodate better pushrod angles on the offset intake rockers.
So it should be no problem to ID a 48* or 59* race block next time you
see one for sale.
The next good way to try to ID a specific MP race block is the MP PART #.
Now firstly let me say, that the #s cast into the sides of a MP race
block mean NOTHING. They are CASTING #s. I know they all begin with the
letter "P" which would lead you to believe it is a MP Part #, but that
is incorrect. The majority of race blocks share the same casting #, so
it does absolutely no good to know it. What you should be looking for is
the 3 digit PART # stamping on the block if it has one. Look on the
drivers side of the block, on the front, opposite to where you find the
X, R, R1, R2 R3 etc logo. If there is a 3 digit # STAMPED into the block
in large #s that is your last 3 digits of the MP PART #. For example if
you have an R3 block and it has a 796 stamped in that area, that block
is a P4876796 59* R3, with 360 mains, 4 bolt mains, and 9.56" deck
height. Now, under the block logo on the passengers side, ie. Under the
R or R1 or R3 logo, you may find a 3 digit # over there. What that is,
is basically the blocks machining production #. Kind of like a VIN # for
blocks. If you have 001 you have the first block of that version ever
machined. 078 and you have #78 etc.
It's pretty obvious to identify 360 or 340 or Ford main journal sizes, so
I won't go into that. Same goes with 4 bolt main caps, if you don't know
what a 4 bolt main cap looks like you should take up pottery or
Now the last big ID challenge is deck height. This is a tough one to
explain in words what to look for. But here are a couple things to keep
in mind. If the block you are looking at has a blank oil filter boss (no
provisions machined for an oil filter NOTE: See Photo #8) the block is
9.025" deck and meant for dry sump use. If it has a complete factory oil
filter boss area, it is either 9.20" or 9.56" deck. So the oil filter
boss area is a dead giveaway for a 9" deck engine. As far as identifying
a 9.20" or 9.56" deck block, that is tougher. Examining the area of
material between the deck and the front water passages is the best way
to know easily. Most of the early blocks were not available in 9.20"
decks, so this generally only applies to R3s.
And then we have the 340 "Resto" block. All a MP 340 "resto" block is, is
a 59 degree tall deck, 340 main, 4 bolt R3 block that has had the extra
8 head bolt bosses per side milled off. (NOTE: See Photo #5) 340 restos
come through machined at 9.59999" deck. (Factory blueprint spec is
9.600") Many "tall deck" race blocks will actually be machined to less
than 9.60" which can make off the shelf piston/Rod combos troublesome.
That is why they are called 9.56" deck blocks, they are meant to be run
at 9.560" square deck or less.
?What are the
differences between W7, W8, and W9 heads, and which one is "best"?
Here is always a fun question to answer. To
begin with I guess I should first state, that you can not generalize any
of these 3 series of cylinder heads. The W7 had somewhere between 13-18
different versions cast in an aprox. 3 year period, and the # of CNC
programs that were done on these heads is outrageous. There are 2
different generations of W8s, with multiple series in each
generation, and then there is the W9 which certainly also is available
in a wide variety of configurations. Let me break down the basics for
W7s. W7s came out in late 1994/very early 1995. The very first
generation stuff is extremely rare and was a true 18 degree cylinder
head. It utilized W2/5 rocker arms, and was essentially just a modified
W5, with a raised intake runner and a square exhaust port. Around Feb
1995 the first 15 degree valve angle heads came out. These also have a
similar appearance to a W5 cylinder head outwardly, and the intake
runner again, can be called by some an "enlarged and elongated" W5
port. They have a very unique combustion chamber shape, and intake short
turn shape. These early W7s still retained W2/5 valve spacing with
larger OD seats that allowed a 2.125" intake valve to be run. They are
drilled for standard W2/5 rocker arm oiling system, but as I said, are
15 degree valve angles, making them a non direct bolt on head for most
59 degree engines. These heads were intended for very early NASCAR
craftsman truck prototype development, as Chrysler was just starting to
get its feet wet back in NASCAR racing. Some very early Craftsman Trucks
actually ran W5 cylinder heads, and the W5 had been campaigned in ARCA
competition, by folks like Bob Keselowski.
Getting back to W7s the next generation W7s took on a life of their
own and started to leave their modified W5 heritage, and became their
own head. The days of using W2/5 rocker arms were over, and the "Lazy
W" W7 rocker system came into fruition, as the W2/5 shaft mount rocker
system had its limitations for high RPM NASCAR use. The standard 5 bolt
rocker hole patterns was not able to maintain valvetrain stability, the
true "Lazy W" bolt pattern uses 12 bolts to hold the rocker stand to the
cylinder head. 8 3/8" bolts and 4 5/16" bolts per head are utilized. The
other major change to the W7 heads at this time was the widening of the
intake ports, and making them shorter and higher off the deck. The W7
evolved into a somewhat standard port window dimension of 2.15" tall,
1.40" wide and 1.35" off the deck.. Previous W7 intake port windows,
were as large as 2.45" tall, 1.45" wide 1.30" off the deck. The exhaust
port on the W7 still remained a large square shape for quite some time.
The valve spacing was widened to allow the use of 2.15" or larger intake
The W7 at this point also went to a big block style dry intake
manifold, with separate valley tray requiring AN style water return
lines. The previous W7s still used a traditional SB Chrysler wet
style intake manifold, with an integral thermostat housing. These
intakes were only made for a short period of time and are extremely hard
to locate today.
Some of these earlier W7 heads were still 10 bolt heads, middle
generation ones evolved and had the 18 bolt "ears" cast on the outside,
but were never drilled/plunge cut for the 18 bolt blocks, and then
finally the later stuff was all setup for 18 head bolts.
The W7 finally evolved a bit more, and the last generation stuff, uses a
D shape Ex port (Early W7 is Square, late W7 is D), and have very small
cast intake ports designed for CNC Porting. The majority of earlier W7s
were designed more around a large casting with hand porting
capabilities, but could be CNC ported depending on the program. The one
other change was an evolution from "Lazy W" rocker arms to the more
familiar today pattern, of the W8/9 staggered rocker pattern which
uses 8 3/8? bolts.
Generalizations about a W7 include: All of them use standard 5 bolt Small
Block Chrysler valve covers. You have to be VERY
cautious when looking at/purchasing a set of W7 heads to know exactly
what you are looking at. Very early stuff as I stated were 18 degree
valve angle heads. MOST W7s however are true 15 degree heads. Some
early stuff used W2/5 rocker arms, some use Lazy W, and some later ones
use W8/9, and there was even a FOURTH rocker arm system that was
utilized for a short period of time. Rocker arms are a major issue for
W7 heads. Be very cautious with these heads, to make sure you know what
rocker arm system your particular set utilizes, and that you can
actually get your hands on a set of rocker bars for your particular
heads. In some extreme cases it may be necessary to send your particular
heads to Jesel or T&D to have custom bars made. As far as head bolts go,
obviously not all W7 heads are 18 bolt heads. In fact probably at least
60% were only 10 bolt heads, so don't ASSume because you are buying a
W7, that you will have 18 bolt capability. Be cautious on the generation
as far as how large of a valve you can install safely due to the spacing
changes. If you buy an early set of 1995 W7s realize that no intake
manifolds exist. You will have to go through the added time and expense
to make a later style W7 dry intake manifold bolt up. Another thing
that varied wildly was overall valve length. There is no one set valve
length for all W7 heads. There were just too many versions made. Same
goes for runner volume and combustion chamber shape/volume. Many
versions were available, although ALL W7s were closed chamber of some
sort. However, they can range wildly from 44 CC chambers all the way to
75+ CC. So be careful there.
Exhaust flange bolt pattern. Again, there were several different
patterns used direct from Chrysler, also a lot of heads were sold
blank and engine builders drilled/tapped their own particular pattern
in a lot of W7s. BUT as a generality, there is one common W7 6 bolt
pattern, it is different from W2/5 or W8/9. It is what I call W7
pattern. It is a straight across 6 bolt pattern. Having adapter flanges
made to use standard W2/5 race headers is not overly difficult.
It doesn't get a whole lot easier when it comes to W8 heads, but at least
not so many different versions were made, but you still must be overly
cautious not to lump all W8s together. W8s were designed purely for
NASCAR Craftsman truck racing. Where as the W7 started life as a NASCAR
truck head, and branched out into World Of Outlaws Sprint Car racing as
well, the W8 was a pure NASCAR head, designed to replace the W7 and some
of its inherent weaknesses. The W8 was used in some Silver Crown type
cars, and I'm sure on some sprint cars here and there over the years,
but it was never designed as a dirt track head.
The original first generation W8s are from the May 1997 Casting run at
Alcoa foundry. The main intent with the W8 head was to produce a much
stronger version of the last generation W7s. W8s are extremely heavy
cylinder heads with massive amounts of aluminum in all areas. They were
designed as a pure 48 degree head with 18 head bolt bosses. They use
W8/9 zig zag rocker pattern. The problem of valve spring to valve cover
interference on the W7 heads, particularly when using large OD springs
was fixed by widening the valve cover rails, which necessitated a
special unique W8 valve cover, and gasket. The intake ports were
slightly raised to 1.50" off the deck. The exhaust ports are also raised
from W7, and use a unique flange bolt pattern. All W8s were cast with
very small chambers, and ports. They are all intended to be CNC ported.
This is not to say that they can NOT be hand, ported, but in reality, I
have only seen ONE set of hand ported W8s in existence (done for
Competition Eliminator). 99% of W8s you will run into are CNC ported by
one company or another. Of the original 1997 castings, there are what
are known as "circle track" and "Drag" heads. There are two big
differences between them. The first is a slightly different exhaust
flange bolt pattern. The pattern looks similar, but is different in
overall dimension. All W8s have a 7 bolt Exhaust flange pattern. The
major change between a drag W8 and a circle track W8 is the valve angle.
Most Drag W8s were 13 degree valve angle, and most circle track W8s are
15 degree. NASCAR limited Chrysler to 15 degree otherwise they would
have ran less valve angle, and testing was done at Arrington racing
engines on sub 15 degree W8s for NASCAR use, but were never run in
In 2000 a second run of W8 castings were made, and this time the foundry
was changed to the Zeus foundry rather than the old standby of Alcoa
Aluminum. A few new changes were added including extra water line
outlets near the deck on the front face of the heads, and these heads
have a 2000 casting date cast into them with slightly different MOPAR
logos. (The logo is smaller)
I should also at this point probably discuss some of the "custom"
castings that also exist, including Comp Eliminator and Lemans type
heads. First off, there are VERY limited amounts of 9 degree W8s that
were cast/machined for use in Pro Stock truck, and NHRA Competition
eliminator. Before these heads ever really hit the P/S scene the P5 head
was released to replace W8 Wedge heads in P/S truck. The 9 degree W8s
would be the some of the rarest of the rare, and also probably the most
powerful W8s in existence. The other "exotic" W8 heads would be some of
the custom castings done for the Chrysler 24 hour of Lemans program.
These include castings with TEN valve cover bolt bosses/holes, and some
have special fuel injector bosses cast right into the top of the intake
port runners, requiring a special custom made valve cover. While rare,
these Lemans heads have recently been dumped onto the market, and
special consideration needs to be made before acquiring a set of these
heads. They also feature slightly taller intake faces, and the port
windows are 1.70" off the deck,and the valve angle is 12 degrees.
Now, as far as ports and chambers in W8s go. Since 99.99% of all W8s
are CNC'd by one company or another it is hard to lump all W8 ports into
any one category. As a generalization, most W8 intake ports will have a
port window somewhere around 2.20" tall, 1.40" wide and 1.50" off the
deck. Runner volumes can vary wildly depending on CNC program and what
the intended purpose of the head was. Some as low as 260 CC intake
runners, some in the near 300 CC range. You have to realize any head CNC
ported for use in NASCAR competition was limited by an exhaust port
height rule by NASCAR. Chapman, Arrington, CFE, M2 etc all have CNC
programs of varying types for W8 heads. Chamber volume can also vary
wildly, and here is where I will also mention the RS head. RS stands
for "Raised Seat". What this basically means is that the valve seats are
not set deep into the combustion chamber when the seat steps are
machined in the raw casting during the machining process. By leaving the
valve seats closer to the deck of the head, it does several things. One
is that it decreases chamber volume significantly, another is that it
adds "artificial" short turn height, and increases runner volume
slightly. Also because the seats are so close to the deck and the
chamber is so shallow, valve unshrouding is greatly reduced. All these
factors add up to increased airflow. There are downsides however. The
first obvious thing is that to maintain the same valve spring installed
height, an RS head requires the use of a longer valve. Generally a W8 RS
head will use a valve length somewhere around 5.75"-5.80" where as a
standard seat W8 head can use a 5.55" valve length and obtain the same
general installed height because the seat to spring pocket height is
reduced. And the other factor in using an RS type head is piston to
valve clearance becomes much more of a critical issue. For the most part
an RS type head requires very deep valve reliefs to be used in the
pistons just die to the simple fact the valve has to travel less
distance to exit the deck surface of the head compared to a standard
seat head. Extremely deep valve reliefs require the top piston ring to
be moved down on the piston, and can sometimes affect piston compression
The reason I had to go into that discussion of RS versus Standard seat
heads is because you most often find the RS option being offered on W8
cylinder heads. This is not to say that it has not or can not be done on
a W7 or W9, but just that it is more rare to see it done on those two
head designs. And getting back to chamber volume, the 9 degree W8s
obviously have the shallowest, smallest chambers out there. Some 9
degree heads will often be in the 20-25 CC range. Most used NASCAR W8 RS
heads will be in the 44-46 CC range, and non RS heads will be in the
52-62 CC range as far as chamber volume goes.
Generally, W8s are considered to be the most sought after of all the W
series heads because more R&D $ was spent on the W8 than any other head,
and the power output as a direct result of the R&D done on those heads
shows up on the track. Most CNC W8s will make substantial power on just
about any combination. However, some are obviously better than others,
with short turn design varying wildly from porting houses such as
Chapman and Arrington. So do not lump all W8s together and think that
one will flow or make as much power as the next. There are spectacular
W8s out there and then there are mediocre W8s out there. So be careful
when selecting a W8 head for your particular application.
As far as intake manifolds go, W8s are just like W7s and 9s in the
fact that they use a shared intake manifold design. It is a dry
manifold design that requires the use of a valley tray, and AN fittings
for water return lines. W7/8/9 Intake manifolds are readily available
from MP in both short deck and tall deck versions.
And last thought on the W8 heads, valve cover availability for these
heads used to be a major factor when purchasing a set of them. MP
offered both an aluminum and a magnesium cast W8 valve cover over the
years and both were extremely expensive. Dealer cost in the $600 range
for the covers alone. Today, much more affordable sheetmetal covers are
available and used Moroso sheetmetal and MP magnesium units are becoming
W9 heads....The most common mistake I see being made when it comes to W9
heads is that there is this common misconception that because a W9 has a
higher # than a W7 or W8, that the W9 MUST be superior to the rest. As I
said, this is a MISCONCEPTION. A W9 head is not necessarily superior to
What is a W9? Simply put a W9 is basically a lightened W8. W9s were
purely intended for sprint car racing. This is why they are so light,
and have down nozzle bosses cast into them. As everyone knows sprint car
racers are fanatical about weight. A W9 is the lightest SB Chrysler
cylinder head ever cast at 21 lbs. The valve cover rails are extremely
thin, the water jackets are extremely large internally, weight was the
major factor in their design. However the intake and exhaust port
locations are basically identical to a W8. This is not to say the ports
are the SAME as a W8, they are not. While W8s were cast very small for
CNC porting, W9s are cast large, to be either CNC'd OR easily hand
ported, or run right out of the box.
W9s share the same rocker arm system with a W8 head. W9s share the
exhaust bolt pattern with circle track W8 heads, so W8 circle track
headers will bolt on a W9. W9s are all cast by ZEUS. Some rare ones
will have a ZAP logo (Zeus Aluminum Products) W9s utilize standard LA
Chrysler valve covers, that will interchange with W2/5/7s etc. W9 heads
come in one basic configuration, with a ~242 CC intake port cast in it.
They come in both 11/32" and 3/"? guide versions, and there is now an
?AB? W9 head that is machined at Chapman Racing Heads, that has 11/32"
CV products guides,and CNC combustion chambers. "Normal" W9s come with
62 CC chambers and non raised seats. Only custom machined W9s will be
RS heads. W9 exhaust ports are cast quite large and in a traditional D
shape. The big benefit of using a W9 head is the fact that they can be
run without being ported, or with minimal hand porting or easily can be
fully hand ported, OR they can be CNC'd for max effort. Where as the W8
really must be CNC'd ie. it's more expensive, plus W8s do not come from
Chrysler with seats or guides installed.
The W9 head is not avail direct from Chrysler in an unmachined state.
W9 is a 48* 18 bolt head, that can be utilized on a 59* block with
modifications. The other nice thing about W9s is the price. Dealer cost
on new bare W9 heads is less than $900 a pair.
There is also now what is known as the W9RP head. RP stands for Raised
Port. This is what is currently being run in World Of Outlaws Sprint Car
410? racing. RP heads are a special W9 casting that comes with no seats
or guides, and no combustion chamber. The spark plug holes are not
machined in as well allowing for ability to move the plug around in the
chamber. These heads are aprox $1800 a pair bare, and require alot of
machine work and must be CNC ported. W9RP heads require custom intake
manifolds, and .725" offset T&D rocker arms. The exhaust side of the
head is the same as a regular W9 head. The intake ports are raised aprox
.800" over a standard W9. It is an 18 bolt 48 degree head that will work
on any 48* race block. They take stock LA valve cover pattern. W9RP head
is best flowing wedge head available for Small Block Chrysler, but along
with the flow and power production comes the biggest expense of any
wedge head. Ryan J.
Performance Race Block, Frequent Machining Problems Identified
In this article I will discuss the most common errors and problems we
encounter on a daily basis with the MP race blocks, just as a
warning for the do it yourselfer out there to watch out for.
These problems are usually small, and can be handled fairly
easily, but are the kind of problems that drive you nuts when
trying to build an engine and one pops up.
The first MAJOR issue I want to identify is the deck height problem on
tall deck race blocks. As you most likely noted these blocks are
referred to as 9.56" deck blocks by MP. The factory blueprint
spec on a 318/340/360 factory block is 9.60" This difference
causes major headaches when trying to use an off the shelf
piston/rod/crank combo that is designed around the factory 9.60"
deck spec. Now I will say this, SOME R3 blocks I have seen have
come in square at 9.60000" right out of the crate. But the
majority of early race blocks and R3s usually have deck height
variation issues. One brand new R3 we just checked recently
started out at 9.595" on the drivers side front of block and
tapered to 9.590" at the rear of the drivers side. The
passengers side was 9.590" at front and 9.595" at rear of pass
side. We square decked it to 9.850" to run it with the pistons
.015" out of hole. I find that these deck height variations from
side to side are common, and the fact that blocks are starting
out at under 9.600" is also very common. MP will tell you these
blocks are intended to be square decked at 9.560" and run at
that deck height or lower. So they are well aware of the issue
of them being under 9.60" As for why they made these blocks a
different blueprint deck height spec than the early production
blocks, I have no idea. The big problem as I noted is in trying
to use an off the shelf Piston/Rod/Crank combo designed for
factory blocks. In the above instance with the piston .015" out
of the hole I was forced to use a .054" thick Cometic head
gasket to make up the difference to obtain proper piston to head
clearance. I could have also flat milled the pistons .015"
Next issue? Crankshaft counterweight to block interference. This seems to
be random. I have seen a bunch of race blocks have this issue
including R1s, R1As and R3s, and some other have more than
enough clearance for the exact same crank. The problem is very
prevalent with the MP forged 4" crank counterweights. The
problem is the undercuts on the front and back side of the main
saddles that are machined for counterweight clearance, generally
are just a hair too shallow, and some modest clearancing with a
die grinder is necessary to take the edge off.
Lifter bore holes. Most of the time on a brand new block, the lifters
will NOT fall through the bores, you can either run a brake hone
through them to take edges off or use a ball broach. I see this
on most every race block.
Oil pan problems. Don't believe what MP claims in their literature that
all race blocks use a 360 oil pan. It's not correct. I'd say
it's 50/50 shot on actually getting a race block that utilizes a
360 pan rear main cap. I've seen R1s with 360 pan, and some
R3s with 340 caps, which according to MP isn't supposed to be,
but it is. So don't be alarmed if your race block has a 340 cap
Also if you plan on running a 59* head and oiling up through the head,
just double check that your race block has been drilled form the
deck through to the #2 and 4 cam journals. I have seen at least
one 59* race block that missed this machining operation.
While we are on the deck of the block again, just be aware that just
because a race block is 48*, do not assume that the extra head
bolt bosses will be drilled and tapped for the 3.8"-16 extra 8
head studs. In fact, MOST are not. A competent machine shop
should be able to drill and tap those holes for you if they have
your head as a template.
And yet still, here is one that is a real problem area. You can not use a
standard 10 bolt Cometic head gasket on an R3 race block. The R3
has an undercut in the lifter valley around the non oiling inner
head bolts. A standard Cometic gasket will overhang the valley
in this area and leak water. You need to use what Cometic calls
their "W2 R3" 10 bolt gasket. It is modified in this area to
The front lifter oil galley holes in the R3 block do not accept a
standard block 19/32" press in plug. You must use a 9/16" plug.
The intermediate shaft. You have two issues here to deal with. First
off, the intermediate shaft bushing will require reaming/honing
to get the shaft in with proper clearance. So don't expect it to
drop right in. I usually just pop it out and replace it with a
new Pioneer products unit. Second more critical issue, is that
on a lot of the R3s we are running into an issue with the gear
hitting the block before it can drop in fully. We are having to
again take the die grinder and clearance the block in this area.
While you are working with your die grinder, don?t forget to add oil
drainback holes in your R3 lifter valley.
Main bore line hone usually way off, so expect to spend the extra $ and
line hone the block.
While your machinist is checking that, have him stick his dial bore gauge
in the cam tunnel as well, we have ran into a couple R3s that
were on the small side there and required honed.
And here are some weird random problems I have personally seen, in no
I've seen a 9.20" deck 59* block that was machined for 48* babbit
I built an R3 that had one of the freeze plug holes that had a casting
flaw, and would have leaked if you just put a plug in it. I had
to epoxy the plug in, to take up the air pocket in the casting.
Occasionally during shipping the rear "ears" on the back of the block
will break off. And fixing this is not as easy as just welding
it back on, you need to get the tranny dowel pin holes lined up
EXACTLY when it gets welded back on.
Some blocks don't come with oil filter diverter plug under the #5 main
cap, so make sure you install it before building.
And here's an interesting one, a customer has a 9.56" deck 360 main R3,
that was machined for a 9" deck timing cover at the top. It was
not drilled for tall deck cover. So I guess the main point of
this article is, you really need to pay attention to EVERY bolt
hole, every machined surface etc in a MP race block. Take
nothing for granted, and do all your clearancing and extra work
BEFORE the block is cleaned for assembly and the cam bearings
are installed. Ryan J.
Using Cometic Head
I decided I better write this article after speaking to several customers
recently, who did not know what Cometic gaskets were, let alone
how to properly install/use them. And I have also seen a lot of
questions about their use on several internet web boards.
First off Cometic is a relatively new gasket company www.cometic.com that
specializes in MLS (Multi Layer Steel) head gaskets. These
gaskets have revolutionized the industry. These gaskets are a 3
piece multi layer steel design that feature embossed rings
around the cylinders and all water/oil passages. The 3 gasket
layers are riveted together with rivets that remain outside the
edges of the block/heads. The two outer layers are coated with a
black rubberized coating. In general you will spend 2 to 3 times
as much on a set of Cometics as you would on the old standby
Fel Pro 1008 head gaskets but you will certainly get 2 to 3
times more life and performance out of them. Cometics are
generally $140-$205 a set depending on what you are buying. The
nice thing about them is they are available in a wide range of
bore sizes and thicknesses. Each set is custom made to the
engine builders desires. Sometimes this is a bad thing in that
it can take a week or more to get a set made and shipped, but
I'd rather have the wide availability in custom sizes rather
than having the wrong gaskets sitting on the shelf. For the
small block Mopar guys like ourselves, they are available in
standard 10 bolt pattern, or the 18 bolt Race block W7/8/9 or
INDY/new B1-BA head pattern. We can have them made with or
without the oil passage up through the heads etc. This is nice
feature, when doing an internal oil setup like an INDY head on a
18 bolt race block. The Fel Pro 18 bolt gaskets do not have an
oil feed hole. But I have had Cometic add that hole for me on 18
bolt gaskets in the past. The varying thicknesses allow me to
play with deck height, and piston combos more so than we would
have been able to in the past as well. Recently I used a set of
.120" thick Cometics to deal with a domed piston and a closed
chamber INDY head. In the past this combo could never have been
ran together, but the Cometic gaskets made it possible.
Customers often ask me what they can do to help seal their head gaskets.
Usually they are blowing regular 1008 Fel Pros and want to know
if there is something better. Well the Cometic is it. If used
properly, you should not have a fire ring sealing issue with a
Cometic gasket EVER. I don't care how much compression you run.
They will seal 17:1+ They are resistant to methanol, race gas,
nitrous oxide etc. Blowers, turbos, big nitrous loads, whatever
you can throw at them, they can take it. These gaskets have made
O rings and copper head gaskets almost obsolete. I don't worry
about fire ring seal on Cometic equipped engines.
Cometics do have to be used properly however to maintain their sealing
capability. Cometic recommends a specific surface finish or
finer on the deck of the block and head surface to seal. This
raises A LOT of questions with racers. Let me just state, that
this surface finish requirement is WAY over rated. Yes it is
true that we try to run as smooth a finish as possible on the
Cometics, but do not get overly concerned if your particular
surface finish does not meet their specs. 98% of the time they
will still seal fine. So don't get caught up in the surface
finish game and feel that your finish is not good enough and
therefore you can't run Cometics. If your heads are FLAT, and
have a decent surface finish, they will seal fine. The only real
weakness they have is sealing water. Every once in a while a
Cometic motor will weep a little bit of water on cold start up,
especially if the surface finish wasn't the best. This being
said, if the deck and heads are flat, have decent finish, and
the heads are torqued properly, wait untill the engine comes up
to operating temp and the weeping should go away. DO NOT use any
type of sealer on the heads, block or the gaskets themselves. I
recommend cleaning the deck of both the block and heads with
either laquer thinner or acetone (Brakleen) right before the
gaskets and heads are installed. We always recommend the use of
ARP head studs, and the use of ARP Moly lubricant on the studs,
nuts, and washers prior to torquing. Do not clean the gaskets
with any chemical, they should remain in the sealed Cometic
packing until the time to use them. And as a precautionary
measure ALWAYS double check and mic both gaskets before using
them to make sure they are the proper thickness. Cometic can,
and has made mistakes in their thicknesses before. It is easily
understandable when they have so many thicknesses to choose
from. So I recommend always measuring to be sure they are right,
otherwise improper piston to head clearance could lead to
One last thing that needs discussed is re-using Cometic head gaskets.
Cometic will not tell you directly that they can be re-used.
However, that is just to protect their bottom line and
reputation in case one were to fail during re-use. My OPINION on
the subject is that as long as you are re-using them on the same
block and same heads that they came off of, and that the
rubberized coating looks to be fully in tact, they can be
re-used safely for a maximum of 3 re-torques.
Again, if they are used properly, Cometic head gaskets can save you a lot
of headaches, and IMO are one of the best products to hit the
market in the past 20 years. Ryan J.