The Ford Barn

tubman · 06-17-2015, 11:59 PM

The post about ID'ing EAB heads got me to thinking. If 8BA or other stock Ford heads are milled to produce the desired .050" squish, are they as good as EAB's, or is there a difference in the cast-in combustion chamber that would make one series better than the other? Also, if aftermarket heads have more than .050" squish, should they be milled, or is there something in the combustion chamber that might be lost?

JWL · 06-18-2015, 05:10 AM

If you read my book you will see the answer to that and many other questions. First it depends on how much is milled and second it depends on the operating range of the engine. However, when talking about stock engines with stock operating ranges, a proper mill job can create similar performances between the 8BA and EAB with the proviso the EAB is NOT milled.

scooder · 06-18-2015, 07:31 AM

I'll answer the second question, any clearance above 0.050" is a waste of space. You'll get a nicer running engine with that quench down tight. Depending on how much was cut, you'll most likely need to make some ignition advance alterations to get that nicer running engine.
I think 0.050" is maximum gap, tighter is nicer.
Johns book has all the answers. Get it if you ain't, read it if you have.
Martin.

Ol' Ron · 06-18-2015, 04:28 PM

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The term "milling the heads" conjures up the impression we're increasing the compression ratio. back in the day we'd do that and thing the reasion the engine ran better was we raised the CR. Milling .020-030" off the heads won't increas the CR very much. The improvement comes from the larger quench area which increased the turbulence in the combustion chamber, thus burning ALL the fuel. It also allows for more ignition advance to burn a leaner mixture in cruise. It also decreses the flame front which prevents spark knock.

06-17-2015, 11:59 PM	#1
tubman Senior Member Join Date: Dec 2013 Location: Minnesota, Florida Keys Posts: 10,320	Milling 8Ba (or even truck ot Mercury heads) The post about ID'ing EAB heads got me to thinking. If 8BA or other stock Ford heads are milled to produce the desired .050" squish, are they as good as EAB's, or is there a difference in the cast-in combustion chamber that would make one series better than the other? Also, if aftermarket heads have more than .050" squish, should they be milled, or is there something in the combustion chamber that might be lost? Last edited by tubman; 06-18-2015 at 12:00 AM. Reason: Can't type very well.

06-18-2015, 05:10 AM	#2
JWL Member Emeritus Join Date: May 2010 Location: Fitzgerald, Georgia Posts: 2,204	Re: Milling 8Ba (or even truck ot Mercury heads) If you read my book you will see the answer to that and many other questions. First it depends on how much is milled and second it depends on the operating range of the engine. However, when talking about stock engines with stock operating ranges, a proper mill job can create similar performances between the 8BA and EAB with the proviso the EAB is NOT milled.

06-18-2015, 07:31 AM	#3
scooder Senior Member Join Date: Jul 2010 Posts: 2,593	Re: Milling 8Ba (or even truck ot Mercury heads) I'll answer the second question, any clearance above 0.050" is a waste of space. You'll get a nicer running engine with that quench down tight. Depending on how much was cut, you'll most likely need to make some ignition advance alterations to get that nicer running engine. I think 0.050" is maximum gap, tighter is nicer. Johns book has all the answers. Get it if you ain't, read it if you have. Martin.

06-18-2015, 04:28 PM	#4
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,861	Re: Milling 8Ba (or even truck ot Mercury heads) Sponsored Links (Register now to hide all advertisements) The term "milling the heads" conjures up the impression we're increasing the compression ratio. back in the day we'd do that and thing the reasion the engine ran better was we raised the CR. Milling .020-030" off the heads won't increas the CR very much. The improvement comes from the larger quench area which increased the turbulence in the combustion chamber, thus burning ALL the fuel. It also allows for more ignition advance to burn a leaner mixture in cruise. It also decreses the flame front which prevents spark knock.