Shaving 4V Open Chamber heads

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wrobinson

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My 13 year old wants to build a 1971-73 Mach 1 Mustang for his first car. We have found a Grabber Blue with white interior base model 1971 Mach 1 to start on.
I want to shave .020 off the virgin 1973 open chamber 4V heads. This is my first 351C build. I know the combustion chambers are huge on the 73 4V head. The .020 cut will square the deck and bump the compression ever so slightly. I am also going to square deck the block by .010-.015. I would suppose zero decking would shave .020-.025 off correct? I would like the compression to be close to 9:1 with the H555P pistons.

 
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You would need to calculate the final combustion chamber volume after the shave to get your final compression ratio. Then with that information and your cam specs you can calc out the dynamic compression ratio. Here is a link to a spreadsheet Don C made up that performs the calcs for you. Two tabs one is for static and the other for dynamic. Don't forget to include adjustment the valve reliefs in the pistions.

https://www.7173mustangs.com/thread-engine-and-compression-calculations?highlight=compression+ratio

 
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4Vforever

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The best thing is to square deck the block with a zero deck height and use flat top Pistons. Work out your desired compression ratio and mill the heads to suit. It's approximately.005" of metal removed from the face for 1cc of chamber volume on an open chamber. The best way of course to get the desired chamber volume is to cc the chambers which is easy to do and doesn't require any expensive tools to do it. 10-10.5:1 compression is achievable with a standard stroke, flat top piston with open chambers. If I can help any more PM me

 
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+1 on 4Vforever's post. I can't find any information on the valve relief volume for that piston. A guess would be 5-6cc. The compression distance is listed as being 1.645 which is .005 less than the nominal stock value of 1.650. Piston manufacturers take significant liberties with compression distances causing changes in compression. The information I have says the nominal stock volume for the D3ZE head is 78cc. 



 
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Just a quick thought. A minimum cut for machining is about .005" on cast. You don't have to machine .020" off to get the compression up as you can do this with piston compression height. For example, my engine was rebuilt using Keith Black KB 177 flat top pistons. These have a compression height of 1.670" compared to stock at 1.650" so there is your .020", leaving just about .008" to clean up your block for zero deck. Mine is an "M" code with cc heads, but that combo gave me a bit too much compression to get it to run without pre-detonation from 91 octane fuel (best I can get here without ethanol). Due to other issues, it had be rebuilt again. This time I used KB 148 pistons. Still zero deck, but with 13cc dish. Dropped the comp ratio to about 9.8:1. A slightly less dish, like 8-10cc would have been perfect, but 13 is what I have so...........

Hope that helped,

Geoff.

 
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4Vforever

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Another way to get your compression up would be to use Cometic MLS head gaskets, not cheap but if you don't want to mill parts, that would be another way around it. They make thicknesses in the .020 "-.030" range. Personally though a flat top piston with a single .002"-.003" single valve relief and the block squared up and a zero deck height is still the best way to go. Any decent machine shop with good equipment can mill any amount off you require, heck I've milled as little as a 1/10 of a thou from heads. You can just hear the cutter touching the surface being milled.

 

wrobinson

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My 13 year old wants to build a 1971-73 Mach 1 Mustang for his first car. We have found a Grabber Blue with white interior base model 1971 Mach 1 to start on.
Well the information I have gathered via the internet is 2CC for every .010 cut. I will CC the ole D3ZE heads to find the true size. The bottom end of the motor has been rebuilt with H555P pistons which would not have been my preference but they are new. Those pistons yield 8.83:1 with 76.2CC head. I would like to be around 9.0:1-9.25:1. I have seen two different numbers for the D3ZE casting heads either 75.4 or 78CC.. So worst case is a .020 cut will put me at 9.0:1. I know I will do at least .010 on the block for square decking.

 
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You are correct, by my calculations every 0.010" of milling equals ~2cc.

Everything I have shows that D3ZE heads are 75.4cc chambers. It appears the 78cc chamber heads were used on 351M/400s.

 
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Well the information I have gathered via the internet is 2CC for every .010 cut. I will CC the ole D3ZE heads to find the true size. The bottom end of the motor has been rebuilt with H555P pistons which would not have been my preference but they are new. Those pistons yield 8.83:1 with 76.2CC head. I would like to be around 9.0:1-9.25:1. I have seen two different numbers for the D3ZE casting heads either 75.4 or 78CC.. So worst case is a .020 cut will put me at 9.0:1. I know I will do at least .010 on the block for square decking.
 So, in my ignorance on engine rebuilding, am I right in thinking that a .020" cut off the heads may mismatch the ports to the intake and possibly need shorter push rods. It could also alter the geometry of the way the heads sit on the block causing the intake not to fit. The lower you go the narrower the distance between them. Slight, but will it matter? I think possibly so.

Instead of doing all that machine work, why not pick up a set of cc heads and save the hassle. You likely will need the valves redone anyway along with seals.

I just looked up those H555P Hyper pistons and they have a compression height of 1.645", so they are lower then stock even. Possibly to allow for a .005" block clean up to arrive at the same deck height as stock, just guessing!

Hey, it's your car do it how you want, but I'd go for different heads. Stock 64cc CC heads would give you about 10.2:1. Ford advertised 10.7:1, but the math doesn't add up the way I looked at it.

 
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You are correct, the pushrod length may need to be shortened to keep the rocker arm contact on the valve stem centered, as well as the correct lifter preload.

The intake manifold may also need to be shaved to match the ports. The top of the block ends, under the ends of the intake manifold, may also need to be shaved so the manifold can sit low enough.

What will happen is that with the combination of decking and shaving the valves will be closer to the pistons. This creates the potential for the valves to possibly contact the pistons, especially with a cam with long duration and high lift.

 
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When i did similar with my 4v heads, engine never wanted start again. Till I figured out the start motor was able to krank that new freshly rebuild Cleveland way too easy. Ordering new pushrods back then ment for me ordinary european, to wait another 3 weeks till new rods would have crossed the pool.

So instead bought precision rings in soft metal with the hole about the size of the pedestal mount bolt, the thickness same as the height of the shaving, cut them both sides to fit the sitting of the pedestal mount u shape. It started right away and till this day, they never gave me problems at all.

 
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You are correct, the pushrod length may need to be shortened to keep the rocker arm contact on the valve stem centered, as well as the correct lifter preload.

The intake manifold may also need to be shaved to match the ports. The top of the block ends, under the ends of the intake manifold, may also need to be shaved so the manifold can sit low enough.

What will happen is that with the combination of decking and shaving the valves will be closer to the pistons. This creates the potential for the valves to possibly contact the pistons, especially with a cam with long duration and high lift.
That's pretty much as I thought then. There is always more to these jobs than first meets the eye.

 

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The D3 4V heads are indeed 78cc as everyone I've encountered has been and Fords own literature backs it up, the earlier D1 4V heads had the 76cc chambers. Best way to compensate for the intake port misalignment is to mill the heads intake face instead of the manifold. Setting up intakes to mill each side is very time consuming and much easier to mill the intake face, plus if you change intakes in the future there no need for to mill it and makes the intake you pulled off easier to sell as it hasn't been milled.  As for rockers if using a hydraulic (as has been stated) if using the standard type rockers, no need to change anything (as long as the parts are in good order) just buy a shim kit that Crane or Ford Racing make and shim up the rockers to achieve correct lifter preload. If going to a bolt on type roller or converting to adjustable valve train, then pushrods may need to be changed to achieve correct rocker geometry. The "thumbprints" on each corner and in the middle on the exhaust side are approximately .060" and is the factory's recommended limit for milling. I've seen Cleveland heads milled at least.020" past that limit on all out race engines without any problems. As for piston to valve clearance using cams with even fairly decent duration you'll be fine, but like anything when building an engine, check everything just to be on the safe side.

 

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I can comment that my heads have probably had 60 thou off (mostly before I had them) and the combustion chamber is down to 63cc. Yes it's down to the 'thumbprints'.

I had material machined off the inlet face instead of the manifold so I can switch manifolds. There is no problem at the ends, still have space there.

Manifold fits ok, may have to take a round file to some bolt holes but not much - had Performer & Torker on so far.

With a mild cam and BB Chevy rockers I previously had shorter pushrods (8.25) but now I have a bigger cam I'm back up to stock length (8.44?).

I wish I had got 20 thou off the block as the L2379 pistons are short comp height.

Have not run it since piston & cam change.

 
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The D3 4V heads are indeed 78cc as everyone I've encountered has been and Fords own literature backs it up, the earlier D1 4V heads had the 76cc chambers. Best way to compensate for the intake port misalignment is to mill the heads intake face instead of the manifold. Setting up intakes to mill each side is very time consuming and much easier to mill the intake face, plus if you change intakes in the future there no need for to mill it and makes the intake you pulled off easier to sell as it hasn't been milled.  As for rockers if using a hydraulic (as has been stated) if using the standard type rockers, no need to change anything (as long as the parts are in good order) just buy a shim kit that Crane or Ford Racing make and shim up the rockers to achieve correct lifter preload. If going to a bolt on type roller or converting to adjustable valve train, then pushrods may need to be changed to achieve correct rocker geometry. The "thumbprints" on each corner and in the middle on the exhaust side are approximately .060" and is the factory's recommended limit for milling. I've seen Cleveland heads milled at least.020" past that limit on all out race engines without any problems. As for piston to valve clearance using cams with even fairly decent duration you'll be fine, but like anything when building an engine, check everything just to be on the safe side.
 Good point to mill the heads' intake face rather than the intake itself. There must be a formula for the amount to remove in relation to the amount removed from the head surface I'm thinking. But the engine machine shop guys should know that.

 
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With Ford V8 pushrod engines it's an easy formula, for every 0.010" removed from the deck or head you remove 0.010" from the intake manifold or head intake surface. This is because on Ford pushrod engines the intake surface is perpendicular (90°) to the block surface and the cylinder banks are also at 90°.

You have to use trigonometry on Chevy, most other GM engines, and on Chrysler engines, because the intake and block surface angles are not perpendicular, and on engines where the cylinder banks are not at 90°, like 60° V6s.

Here's an article about it:

http://victorylibrary.com/mopar/intake-mill-c.htm

 
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With Ford V8 pushrod engines it's an easy formula, for every 0.010" removed from the deck or head you remove 0.010" from the intake manifold or head intake surface. This is because on Ford pushrod engines the intake surface is perpendicular (90°) to the block surface and the cylinder banks are also at 90°.

You have to use trigonometry on Chevy, most other GM engines, and on Chrysler engines, because the intake and block surface angles are not perpendicular, and on engines where the cylinder banks are not at 90°, like 60° V6s.

Here's an article about it:

http://victorylibrary.com/mopar/intake-mill-c.htm
 Somehow I just knew it would be simple on a Ford!! Another reason NOT to buy Chevy.

 Good info again Don, Thanks.

 
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