Milling heads

[05stroker]

I took .005 off my heads. How much will it change CR? Im thinking not much but want to know for sure.

 

[05moneypit]

http://www.wallaceracing.com/cr_test2.php

Without actually cc'ing the combustion chambers it is only a guess. Stock chambers are 53 cc I believe. Compressed OEM headd gasket is about .038 if I remember correctly. Try running the calculator and changing the head gasket thickness by .005. You are most likely looking at about .1 or so increase.

 

[05stroker]

http://www.wallaceracing.com/cr_test2.php

Without actually cc'ing the combustion chambers it is only a guess. Stock chambers are 53 cc I believe. Compressed OEM headd gasket is about .038 if I remember correctly. Try running the calculator and changing the head gasket thickness by .005. You are most likely looking at about .1 or so increase.

Calculator is not working for me . I have stock overbore head gaskets with stock combustion chambers, -18 cc pistons, 3.582 bore. It has always showed 9:1 CR before

 

[05stroker]

This one made it easier. Add you are correct. Looks like I am 9.2 C/R now instead of the 9.1 C/r I was before. Thanks

http://www.summitracing.com/expertadviceandnews/calcsandtools/compression-calculator

 

[marcspaz]

It will likely be unmeasurable at 5,000ths of an inch.

 

[05stroker]

It will likely be unmeasurable at 5,000ths of an inch.

On the calculator I listed It says 9.12:1 before and 9.21:1. All I did was take .005 of the head gasket.

 

[05moneypit]

I just got home from work and measured an old head gasket. It measures .034 thick. I'm using standard bore head gaskets so the diameter is 92mm or 3.622. Taking .005 of the gasket thickness is only a ballpark number since the combustion chamber is really a cylinder. You most likely only raised the CR .05 or so....but you did raise it so MORE POWER......lol

 

[05stroker]

I just got home from work and measured an old head gasket. It measures .034 thick. I'm using standard bore head gaskets so the diameter is 92mm or 3.622. Taking .005 of the gasket thickness is only a ballpark number since the combustion chamber is really a cylinder. You most likely only raised the CR .05 or so....but you did raise it so MORE POWER......lol

Maybe I should have had them take .020! I am on E85 now. LOL

 

[BruceH]

FYI the stock chamber is 50.3 cc. FRPP stage 2 are 53cc and the stage 3 are 48cc.

Is the motor back together Billy? Got the key situation figured out?

 

[stkjock]

Bruce, ck the "go fast thread"

 

[BruceH]

Bruce, ck the "go fast thread"

I was just coming back to edit my post after seeing it there. Thanks Dave.

 

[PNR Welding]

My heads are livernoise stage 3. 51cc heads.
I took .012 off bringing them down to 48cc with a .021 head gasket. Raising my cr from 9.5 to 10.1 to 1.
I wanted that free power without
Changing pistons. Lol


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[Sonicblue_s197]

Iv been thinking of milling the heads also, I'm at 10.0:1 right now . Would it be worth it? I'm on 18-19 pounds with the F1A on e85, how much can you gain from that?

 

[BruceH]

Iv been thinking of milling the heads also, I'm at 10.0:1 right now . Would it be worth it? I'm on 18-19 pounds with the F1A on e85, how much can you gain from that?

http://www.wallaceracing.com/Calculators.htm

 

[05stroker]

That puts mine at a 9.12:1 now vrs the 9.03:1 I was at before. Free power! LOL

 

[RED09GT]

Am I correct in assuming that the chain tensioners will be able to make up the slack for head and/or deck milling?
Anything else that needs to be accounted for-other than piston to valve clearance?
I picked up a set of 15 cc diamond pistons and still trying to decide whether to use them or sell them.



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[oldlugs]

I can't imagine that taking .005" off the heads will make a noticeable change in anything. With that little removed (and how can so little be cut off?), I'm sure the heads would still be considered within factory "stock" specs. .005" is practically nothing.

Sure that wasn't .05" (fifty thou)? That amount would be more typical of a cleanup cut to get 'em flat again.

 

[BruceH]

I can't imagine that taking .005" off the heads will make a noticeable change in anything. With that little removed (and how can so little be cut off?), I'm sure the heads would still be considered within factory "stock" specs. .005" is practically nothing.

Sure that wasn't .05" (fifty thou)? That amount would be more typical of a cleanup cut to get 'em flat again.

The Ford spec is no more than .001" in a 1.5 square inch area. .005" variation is quite a bit and would cause the mls gaskets to not seal. One of my blocks needed .005" to clean up. It made a difference of .14 in the compression ratio. .050" would bump the compression 1.28.

 

[SNKPWR]

Wouldn't .005" off the head cause less loss of combustion chamber volume than losing .005" of head gasket? I mean the combustion chamber volume is cylindrical while the other is some amount less than that. Still pretty neglible I would think.

 

[RED09GT]

Wouldn't .005" off the head cause less loss of combustion chamber volume than losing .005" of head gasket? I mean the combustion chamber volume is cylindrical while the other is some amount less than that. Still pretty neglible I would think.

It would be a lot less as the combustion chamber doesn't have as much volume as the head gasket. Aftermarket heads for SBF's often list the amount of cc's lost for x amount of flat milling or x amount for angle milling.

I would take the data from againstallodds1's post where he states the change in volume from milling .012" off and do the math for a better approximation-or just measure it while doing the build.

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