Will Eddy 84cc RPM Heads lower or increase my 10 to 1 compression 440 engine?

[1Bad70Charger]

My 69 Road Runner with its 440 engine is making about 10 to 1 compression as it was built to stock specs.

Assuming I am at 10 to 1 compression with stock iron heads (not certain what heads I have didn't build the engine but let assume the heads that came on a 1969 440 engine in a B-Body car), will the Eddy 84cc heads increase or lower my compression and by how much if I use a functional head gasket that will help me keep compression as high as possible?

Thanks in advance!  

[471_Magnum]

Iron heads are about 88cc, so your compression will up slighty.

More importantly, the Eddys will dissipate heat faster, lowering your thermal efficiency. Rule of thumb is that aluminum heats effectively lower compression ratio by one point.

The loss in thermal efficiency will be more than made up by the improved flow though.

[John_Kunkel]

If the 440 in question actually has the original piston spec and the original 906 heads the compression will be about a half-point low from the gitgo so you're starting with 9.5 instead of 10.

If the motor was rebuilt with the common off-the-shelf replacement pistons and a thicker head gasket the compression will be even lower to start.

[firefighter3931]

There's allways the option of milling the heads to reduce chamber volume which increases static compression. 


Ron

[1Bad70Charger]

There's allways the option of milling the heads to reduce chamber volume which increases static compression.  


Ron

Ron,

I thought about that and its a great option but didn't know if the Eddy Heads could be milled enough to make a difference.

What is the most I can have the Eddy alum Heads Milled from 84 cc to  ?  


Thank you Ron (and everyone else) who responds here.  

[RECHRGD]

There's allways the option of milling the heads to reduce chamber volume which increases static compression. 


Ron

Ron,

I thought about that and its a great option but didn't know if the Eddy Heads could be milled enough to make a difference.

What is the most I can have the Eddy alum Heads Milled from 84 cc to  ?   


Thank you Ron (and everyone else) who rresponds here.   

I had mine shaved by 50 thousands and went from around an average of 140 lbs of cylinder pressure to 175 lbs..  Remember that you'll need to have the intake shaved to match the heads.  I don't have the measurement of the chamber volume change though.  Bob

[1Bad70Charger]

There's allways the option of milling the heads to reduce chamber volume which increases static compression.  


Ron

Ron,

I thought about that and its a great option but didn't know if the Eddy Heads could be milled enough to make a difference.

What is the most I can have the Eddy alum Heads Milled from 84 cc to  ?  


Thank you Ron (and everyone else) who rresponds here.  

I had mine shaved by 50 thousands and went from around an average of 140 lbs of cylinder pressure to 175 lbs..  Remember that you'll need to have the intake shaved to match the heads.  I don't have the measurement of the chamber volume change though.  Bob

Great info, does anyone else have any feedback how much the Eddy 84cc heads can be safely milled on a n/aspirated engine and what does that lower the combustion chamber size to (84cc down to ?)

[1Bad70Charger]

There's allways the option of milling the heads to reduce chamber volume which increases static compression.  


Ron

Ron,

I thought about that and its a great option but didn't know if the Eddy Heads could be milled enough to make a difference.

What is the most I can have the Eddy alum Heads Milled from 84 cc to  ?  


Thank you Ron (and everyone else) who rresponds here.  

I had mine shaved by 50 thousands and went from around an average of 140 lbs of cylinder pressure to 175 lbs..  Remember that you'll need to have the intake shaved to match the heads.  I don't have the measurement of the chamber volume change though.  Bob

Great info, does anyone else have any feedback how much the Eddy 84cc heads can be safely milled on a n/aspirated engine and what does that lower the combustion chamber size to (84cc down to ?)

Don't be shy to answer with an educated response gentleman.  

You can throw a grenade in this performance section and nobody would be harmed!    

Hopefully, everyone is out enjoying their Mopars in the end of this 2010 summer. I know I will be driving mine to a cruise night in 10 minutes!   Enjoy those Mopars over the  Holiday weekend and have a good one! 

[John_Kunkel]

I would question the wisdom of milling a brand new set of heads and hasseling with the manifold alignment, etc. Just my 

[Roger 68 charger]

I would question the wisdom of milling a brand new set of heads and hasseling with the manifold alignment, etc. Just my 

I would have to agree with John---I just received my RPM heads back from the machine shop--Brand new they were 84cc but I had them CNCed ported and 2.19 intack valves installed which they are now 88.8cc--I was going to use a dished piston for my stroker kit but with a 88.8cc I went with the flat tops to keep the compression up--Maybe you could use a thinner head gasket

[RECHRGD]

I would question the wisdom of milling a brand new set of heads and hasseling with the manifold alignment, etc. Just my 

Every situation is different.  I was always under the assumption that I had different pistons than I did.  I found out that I had less compression than I had thought.  I was only doing a head/cam change so it made sense to me at the time to mill them to get the performance I was after without tearing down the whole engine.  It worked.  Bob

[firefighter3931]

I would question the wisdom of milling a brand new set of heads and hasseling with the manifold alignment, etc. Just my 

Every situation is different.  I was always under the assumption that I had different pistons than I did.  I found out that I had less compression than I had thought.  I was only doing a head/cam change so it made sense to me at the time to mill them to get the performance I was after without tearing down the whole engine.  It worked.  Bob

I agree with Bob....make the heads work for your build. 

The original poster has a nice shortblock that just recently checked out good on compression testing so there's no reason to tear down the block if the desired results can be achieved through other means. 

A .040 shave should remove ~10cc of chamber volume.



Ron

[greenpigs]

   My computer software says the site is unsafe but I have not had any problems. This may help you figure out how much you will need to mill off the heads. The numbers are for a SB chevy so you will need some info plus a few other measured values to get an accurate calculation.   http://www.wheelspin.net/calc/calc2.html

[1Bad70Charger]

I would question the wisdom of milling a brand new set of heads and hasseling with the manifold alignment, etc. Just my  

Every situation is different.  I was always under the assumption that I had different pistons than I did.  I found out that I had less compression than I had thought.  I was only doing a head/cam change so it made sense to me at the time to mill them to get the performance I was after without tearing down the whole engine.  It worked.  Bob

I agree with Bob....make the heads work for your build.  

The original poster has a nice shortblock that just recently checked out good on compression testing so there's no reason to tear down the block if the desired results can be achieved through other means.  

A .040 shave should remove ~10cc of chamber volume.



Ron

Great info guys I appreciate it!  

Ron (or anyone else) if my engine is making let's say 9 to 1 compression, and I milled the Eddy Heads from 84 cc down to 74 cc by shaving the .040 you referenced above, with also using the thinnest head gasket I can safely/reliably use, what would that (approximately) bump up my compression to?  

[BSB67]

I would question the wisdom of milling a brand new set of heads and hasseling with the manifold alignment, etc. Just my  

Every situation is different.  I was always under the assumption that I had different pistons than I did.  I found out that I had less compression than I had thought.  I was only doing a head/cam change so it made sense to me at the time to mill them to get the performance I was after without tearing down the whole engine.  It worked.  Bob

I agree with Bob....make the heads work for your build.  

The original poster has a nice shortblock that just recently checked out good on compression testing so there's no reason to tear down the block if the desired results can be achieved through other means.  

A .040 shave should remove ~10cc of chamber volume.



Ron

Great info guys I appreciate it!  

Ron (or anyone else) if my engine is making let's say 9 to 1 compression, and I milled the Eddy Heads from 84 cc down to 74 cc by shaving the .040 you referenced above, with also using the thinnest head gasket I can safely/reliably use, what would that (approximately) bump up my compression to?  

Using the same gasket in both cases, about 9.8:1.

[1Bad70Charger]

I would question the wisdom of milling a brand new set of heads and hasseling with the manifold alignment, etc. Just my  

Every situation is different.  I was always under the assumption that I had different pistons than I did.  I found out that I had less compression than I had thought.  I was only doing a head/cam change so it made sense to me at the time to mill them to get the performance I was after without tearing down the whole engine.  It worked.  Bob

I agree with Bob....make the heads work for your build.  

The original poster has a nice shortblock that just recently checked out good on compression testing so there's no reason to tear down the block if the desired results can be achieved through other means.  

A .040 shave should remove ~10cc of chamber volume.



Ron

Great info guys I appreciate it!  

Ron (or anyone else) if my engine is making let's say 9 to 1 compression, and I milled the Eddy Heads from 84 cc down to 74 cc by shaving the .040 you referenced above, with also using the thinnest head gasket I can safely/reliably use, what would that (approximately) bump up my compression to?  

Using the same gasket in both cases, about 9.8:1.

Me likey the sound of that.   

Assuming my motor has an oem head gasket on it and I go as thin as I can reliably go how close can we get to
10:0 to 1 compression (we are getting close). 

[greenpigs]

OEM is .020 I think and the Edelbrock is about twice as thick so unless someone makes a thinner gasket you may need to remove even more material from the heads.

[1Bad70Charger]

OEM is .020 I think and the Edelbrock is about twice as thick so unless someone makes a thinner gasket you may need to remove even more material from the heads.

I would think that some other after market manufacturer makes a thinner head gasket than oem.

Doesn't a company like Felpro offer this or are they strictly GM stuff? 

Would be surprised if you couldn't get a thinner than normal head gasket from some company like Felpro (just assumed that would be a given but not the end of the world if not, would just use what's available (not the end of the world if not, as I would just use what is dependable and not junk) and would probably not want to shave more than .050 off brand new Eddy heads. 

[BSB67]

What is the thickness of the gasket you have now?

[1Bad70Charger]

What is the thickness of the gasket you have now?

Did not build engine bought the car how she sits (69 1/2 Roadrunner 6 pack A12 Tribute car without the 6 pack) and have had no reason to pull off the heads as she has been a reliable cruiser.

I was told (but no documentation) from the guy I bought it from last year, that the guy he bought it from told him it was a stock 440, built to stock specs, with slightly hotter cam (which I can tell it does have).
Of course without no documentation I can only assume that it has what the stock oem head gaskets would be on most late 60s and early 1970 440 engines as built from the factory.  

[greenpigs]

I did a search at Summit and found thishttp://www.summitracing.com/parts/EDL-60929/SuggestedParts/?query=Department%7cGaskets%7cPart+Type%7cHead+Gaskets Back in the day they used the steel shim gasket so you really are just at where it was originally if it has the steel shim. The two listed are .038 & .039 compressed thickness so before milling the heads it would be a good idea to pull it apart and see where you are at. To get gasket thickness and deck height so you only have to do it once and get it right.

[1Bad70Charger]

I did a search at Summit and found thishttp://www.summitracing.com/parts/EDL-60929/SuggestedParts/?query=Department%7cGaskets%7cPart+Type%7cHead+Gaskets Back in the day they used the steel shim gasket so you really are just at where it was originally if it has the steel shim. The two listed are .038 & .039 compressed thickness so before milling the heads it would be a good idea to pull it apart and see where you are at. To get gasket thickness and deck height so you only have to do it once and get it right.

As always, great stuff Greenpigs! 

On the average, from a professional auto engine (machine shop), what should I expect to pay (approximately) to have heads milled by .050?

Thanks for all the input here gentleman! 

[1Bad70Charger]

There's allways the option of milling the heads to reduce chamber volume which increases static compression.  


Ron

Ron or any other knowledgeable Mopar enthusiast:

If I mill my brand new 84cc Eddy Alum. heads to reduce chamber volume and increase static compression can I still use my stock oem rockers that are in good shape, as I am planning to reuse them on my top end build, as I am using a K58/60 Engle Cam, with .537 lift (which is compatible with oem rockers as you know).  I  was left with the impression after talking with a knowledgable Mopar engine builder that if I mill the heads then I will have to switch to an aftermarket adjustable rocker arm.

Is this accurate info, or did I misunderstand him and I will still be able to resuse my oem stock (non-adjustable) rockers if I Mill my Eddy Heads say between .050 and .070?

I do know that I will have to have my Holley Street Dominator intake manifold shaved to match the heads (if i have them milled).

Thanks in advance.  

[greenpigs]

  I think the builder meant you can not adjust with the stock setup after removing that much material. However you could go with custom length pushrods. Did you get the DVD listed on this site on how to tune? If not you should and he will walk through on how to measure this so you can get the correct length. It might not be whatever material was removed. Meaning if you take .070 off the heads you get pushrods .070 shorter than stock, it may be close but not ideal.

[Challenger340]

The "stock" length Pushrods will NOT work, when Milling .050-.070 off the Heads and re-using oem Rocker Arms.
They will collapse the Lifter Plunger and Hold Valves open.

In theory anyways,
when milling the Heads by a set amount, purchasing a set of shorter Pushrods(by the same amount milled from the Heads) should work,
however,
it's up to the Guy assembling the Engine to Insure the "correct" amount of Lifter Plunger Preload is obtained with the "new" length Pushrods,
and,
that "whatever" length Pushrod provides the above correct lifter preload,
also,
insures proper Valve Tip geometry through the Lift cycle, something the Stock OEM Rockers do not provide above .500" lift, especially when moving to an aftermarket HOTROD Camshaft Lifts & Rates ?
You can expect accelerated Valve Guide wear on the new Eddy Heads with OEM Rockers for that reason.

Of secondary concern here, (for me anyways),
is that even "if" all of the above checks good with new shorter Pushrods ?

**What is the "reliability" of the stock OEM Rockers(100,000 mile used or "new"), in an application they were never intended for, that being 120# Seat Pressure and ~300# open Valve Spring Rates ? or the Higher RPM's being spun ?
IMO,
NOT GOOD !

At the VERY least, IMO,
you should consider some "6-Pack" style, THICKER stamped Steel OEM Rockers should be obtained, and as far as I know they are long since gone NLA on the parts books ? I may be wrong ?
Because,
The Stock, NON "6 Pack" OEM Rocker Stampings(thinner), were famous for the Pushrod punching Holes through the Pushrod Cup portion of the Rocker with bigger camshafts/V-Spring Rates @ rpm ?

I'm not even sure the thicker "6-Pack" OEM Rocker Stampings, are not going to prove problematic at some point, "IF" they can be found ?

In My Opinion Only,
"BEST" procedure, when Milling a set of Heads .050-.070 to increase Compression,
and,
using an Aftermarket Camshaft of those Lift/Spring Rate events and intended RPM range,
is to obtain some;
** Ductile Iron Adjustable Rocker Arms
** "Cut to length" Pushrods, Cup & Ball Ends, for the above Ductile Iron Rockers.

No Wars wanted, just my opinions.
Bob.