The Ford Barn

34pickup · 01-17-2018, 02:27 PM

I had read that the cast iron heads on a 34 truck had a higher compression ratio than the aluminum heads used on cars. Is this true or just more disinformation on the internet?

flatheadmurre · 01-17-2018, 02:43 PM

If i remember right the chamber volume of the cast iron heads are bigger...
I might be wrong but i think it´s 60 for aluminum and 80 for the cast iron heads.

34pickup · 01-17-2018, 05:17 PM

Thanks

Lawrie · 01-17-2018, 06:32 PM

Look in the green bible parts book,or the service bulletins,In mine it shows a list of the head part numbers cast iron or alloy and the chamber volume also the comp ratio.
Lawrie

rotorwrench · 01-17-2018, 06:49 PM

There is a compression ratio chart over on the HAMB that covers just about every head made by Ford plus a bunch of aftermarket ones and all the different stroke combinations. It's about 5 pages worth and took a lot of research to put it all together. This is a link to where it can be down loaded. https://www.jalopyjournal.com/forum/...hoices.482189/

DavidG · 01-17-2018, 07:42 PM

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That is one serious amount of information gathering requiring a lot of effort, patience, and perseverance.

34pickup · 01-18-2018, 10:44 AM

Thanks for the info

JSeery · 01-18-2018, 11:12 AM

Believe these are the Green Book values.

Talkwrench · 01-18-2018, 06:51 PM

Damn I knew my [21 stud] heads were good ; ) 7.5:1

flatjack9 · 01-18-2018, 10:58 PM

The pistons must have been different for the aluminum and iron head engines because even with that huge difference in volume, the c.r. is the same.

Ol' Ron · 01-18-2018, 11:09 PM

The chart represents the factory specs. However, they're all over the place, so measure them.

Mike51Merc · 01-19-2018, 09:00 AM

I had heard that the aluminum "Denver" heads had the most compression because of the high elevation. Here's a chart I found in the internet years ago.

01-17-2018, 02:27 PM	#1
34pickup Senior Member Join Date: May 2010 Location: Huntsville Al Posts: 1,526	Difference in compression ratio on cast iron heads? I had read that the cast iron heads on a 34 truck had a higher compression ratio than the aluminum heads used on cars. Is this true or just more disinformation on the internet? __________________ Matt 24:36-41

01-17-2018, 02:43 PM	#2
flatheadmurre Senior Member Join Date: Apr 2015 Location: Sweden Posts: 3,045	Re: Difference in compression ratio on cast iron heads? If i remember right the chamber volume of the cast iron heads are bigger... I might be wrong but i think it´s 60 for aluminum and 80 for the cast iron heads.

01-17-2018, 05:17 PM	#3
34pickup Senior Member Join Date: May 2010 Location: Huntsville Al Posts: 1,526	Re: Difference in compression ratio on cast iron heads? Thanks __________________ Matt 24:36-41

01-17-2018, 06:32 PM	#4
Lawrie Senior Member Join Date: May 2010 Location: Qld, Australia Posts: 4,215	Re: Difference in compression ratio on cast iron heads? Look in the green bible parts book,or the service bulletins,In mine it shows a list of the head part numbers cast iron or alloy and the chamber volume also the comp ratio. Lawrie

01-17-2018, 06:49 PM	#5
rotorwrench Senior Member Join Date: Jun 2010 Location: San Antonio, Texas Posts: 16,427	Re: Difference in compression ratio on cast iron heads? There is a compression ratio chart over on the HAMB that covers just about every head made by Ford plus a bunch of aftermarket ones and all the different stroke combinations. It's about 5 pages worth and took a lot of research to put it all together. This is a link to where it can be down loaded. https://www.jalopyjournal.com/forum/...hoices.482189/

01-17-2018, 07:42 PM	#6
DavidG Senior Member Join Date: May 2010 Location: southeastern Michigan Posts: 10,101	Re: Difference in compression ratio on cast iron heads? Sponsored Links (Register now to hide all advertisements) That is one serious amount of information gathering requiring a lot of effort, patience, and perseverance.

01-18-2018, 10:44 AM	#7
34pickup Senior Member Join Date: May 2010 Location: Huntsville Al Posts: 1,526	Re: Difference in compression ratio on cast iron heads? Thanks for the info __________________ Matt 24:36-41

01-18-2018, 06:51 PM	#9
Talkwrench Senior Member Join Date: Aug 2012 Location: Perth, Western Australia Posts: 2,687	Re: Difference in compression ratio on cast iron heads? Damn I knew my [21 stud] heads were good ; ) 7.5:1 __________________ *"Came too close to dying to stop living now!"*

01-18-2018, 10:58 PM	#10
flatjack9 Senior Member Join Date: May 2010 Location: Oshkosh, Wi Posts: 4,526	Re: Difference in compression ratio on cast iron heads? The pistons must have been different for the aluminum and iron head engines because even with that huge difference in volume, the c.r. is the same.

01-18-2018, 11:09 PM	#11
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,860	Re: Difference in compression ratio on cast iron heads? The chart represents the factory specs. However, they're all over the place, so measure them.