What head is this?

[1stWoody]

Can anyone tell me about this?
It appears to be a 5.2:1 head but it does not have a "B" cast into it.

[Gary WA]

Is a high comp head! Made in the good ole USA. Clean it up good inside and out and use it!

[stickshift]

Looks like a police head, wonder why it isn't marked with a "B" See info.
https://www.fordgarage.com/pages/hea...ssionratio.htm

[1stWoody]

Originally Posted by stickshift

Looks like a police head, wonder why it isn't marked with a "B" See info.
https://www.fordgarage.com/pages/hea...ssionratio.htm

Yeah I was on that site earlier looking for info.

[1930artdeco]

Aftermarket head more than likely. But still Hi compression.

[JayJay]

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As Vince Falter's most excellent web page notes (see Stickshift's post #3) there are a lot of aftermarket heads. I have a "Model A" aftermarket head on my '31, which apparently came in both 4.2 and 5.2 configuration. I pulled the head off last week to change the head gasket and sure enough, I have the "high compression" version. I put that in quotes because a 5.2 compression ratio ought to put cylinder pressure somewhere in the 70's psi. Well, I have 80s and 92 in one cylinder! I suspect that the block and head have been decked sometime in the past, the engine is 0.080" overbore so it likely has been rebuilt at least twice and the block possibly decked each time. The head appears flat, I used a 0.003" feeler gauge and a straightedge and could not get it in anywhere, either lengthwise or crosswise. So I'm going to put it back together (after I get the broken stud out, of course...) and run with it.

JayJay

[stickshift]

Most likely the head listed as "F2 MF" on the spreadsheet list. Copy of a Ford 5.2 A-6050-B police head.

[Gene F]

Originally Posted by JayJay

As Vince Falter's most excellent web page notes (see Stickshift's post #3) there are a lot of aftermarket heads. I have a "Model A" aftermarket head on my '31, which apparently came in both 4.2 and 5.2 configuration. I pulled the head off last week to change the head gasket and sure enough, I have the "high compression" version. I put that in quotes because a 5.2 compression ratio ought to put cylinder pressure somewhere in the 70's psi. Well, I have 80s and 92 in one cylinder! I suspect that the block and head have been decked sometime in the past, the engine is 0.080" overbore so it likely has been rebuilt at least twice and the block possibly decked each time. The head appears flat, I used a 0.003" feeler gauge and a straightedge and could not get it in anywhere, either lengthwise or crosswise. So I'm going to put it back together (after I get the broken stud out, of course...) and run with it.

JayJay

I have a Brumfield. So how do you measure these things for compression ratio?

[Y-Blockhead]

Originally Posted by Gene F

I have a Brumfield. So how do you measure these things for compression ratio?

Cylinder Displacement + Combustion Chamber Volume / Combustion Chamber Volume = Theoretical Compression Ratio.

[JayJay]

Originally Posted by Y-Blockhead

Cylinder Displacement + Combustion Chamber Volume / Combustion Chamber Volume = Theoretical Compression Ratio.

Y-B has given the definition of compression ratio. Practically speaking, most folks simplify it as

*measured compression test pressure divided by 14.7 = compression ratio.

So the "standard" psi of say 62 psi would be 62/14.7 = 4.22 (round to 4.2). And a 5.2 head would be around 75 psi on a compression test.

JayJay

[Y-Blockhead]

Originally Posted by JayJay

Y-B has given the definition of compression ratio. Practically speaking, most folks simplify it as

*measured compression test pressure divided by 14.7 = compression ratio.

So the "standard" psi of say 62 psi would be 62/14.7 = 4.22 (round to 4.2). And a 5.2 head would be around 75 psi on a compression test.

JayJay

No, what I gave him is the equation to find his Theoretical Compression Ratio.

Too many variables in way you suggest.

[JayJay]

Originally Posted by Y-Blockhead

Too many variables in way you suggest.

I agree completely. I'm not suggesting to use it, but it's simple and what a lot of folks can relate to easily. That method doesn't account for the difference between absolute (the 14.7) and gauge (what you measure) pressures, for example.

And the 14.7 only applies at sea level.

JayJay

[1stWoody]

So after leaving the head in a rust911 solution for a day and cleaning off I think I know why it was sitting on the shelf. It has cracks across the top of the head and I don't trust it enough to try it out.

[katy]

Looks like freeze cracks to me. If there is no other cracks I would solder them up and give it a try.

[1stWoody]

I thought about grinding out the cracks a little and using some JB but I'm worried about the crack near the #2 spark plug especially with the higher compression.

[jack backer]

5.2? How about a Winfield red head? 7.5 to 1…she’ll pull your hat clean off your head.

[Gene F]

Thanks Jay Jay

[40 Deluxe]

Originally Posted by JayJay

I agree completely. I'm not suggesting to use it, but it's simple and what a lot of folks can relate to easily. That method doesn't account for the difference between absolute (the 14.7) and gauge (what you measure) pressures, for example.

And the 14.7 only applies at sea level.

JayJay

Plus, cranking speed varies, ring seal may not be very good, valve timing varies (affected by lash), ambient temperature and coolant temperature vary, etc., so the compression gauge method is a waste of time!

[JayJay]

Originally Posted by 40 Deluxe

Plus, cranking speed varies, ring seal may not be very good, valve timing varies (affected by lash), ambient temperature and coolant temperature vary, etc., so the compression gauge method is a waste of time!

And let's add - overbore increases cylinder displacement relative to combustion chamber volume.

All in all, a lot of variables. That many degrees of freedom makes the engineer in me cringe. Having said all that, it's an attractively simple formula. And it's at least qualitatively correct - compression ratio and cylinder pressure do co-vary.

I think you, Y-B and I all violently agree.

JayJay

[old Tom]

I have a red winfield been tested and resurfaced is ir worth much> had fir 50 yeara,