The Ford Barn

Scott McDermott · 03-22-2023, 06:39 AM

I need to rebuild my 37 FH. If possible, I'd like to bump up the compression, but I'm not finding any options for piston/heads to do so. I am aware of the Sharp heads, but $1500 is a bit steep. Are there any other options or should I just build back original?

Bored&Stroked · 03-22-2023, 07:18 AM

Without spending too much money, you can check the compression height above the pistons and if it is over .045, then have the heads milled to bring the clearances down to .040 to .050. Flatheads like a tight squish area. Other than making extensive changes to increase the cubic inches (stroker crank of some sort) or doing additional modifications to the heads (filling in the transfer area), there are no other easy and inexpensive ways to go about it.

Other performance things to consider are a mild CAM, improved ignition curve (mods to the distributor), new intake and dual carbs and exhaust.

Ol' Ron · 03-22-2023, 07:19 AM

Angle mill the stock heads.

Scott McDermott · 03-22-2023, 08:12 AM

Thanks B&S and Ol' Ron. I probably should have written a little more in my original post. I planned on two 97's along with a Isky Max-1 Cam and recurve dizzy. I've previously changed over to Pertoronix 12V and built a 2" dual exhaust. When I couldn't find head/piston options I was concerned the cam and carbs would be of little value if the compression wasn't increased. Any idea what a ballpark CR would be after milling the heads?

Lawson Cox · 03-22-2023, 09:30 AM

Quote:

Originally Posted by Scott McDermott

I need to rebuild my 37 FH. If possible, I'd like to bump up the compression, but I'm not finding any options for piston/heads to do so. I am aware of the Sharp heads, but $1500 is a bit steep. Are there any other options or should I just build back original?

You could put the whole thing under a 10 ton press and compress it that way.

(Sorry for the poor pun. The devil made me do it.)

Bill OH · 03-22-2023, 12:09 PM

Sponsored Links (Register now to hide all advertisements)

I have a 221 +.030, dual 97s, Max 1 cam, pockets milled into the heads for the valves, dual exhaust, timing marks by the hard stop method, 45 main jets , 71 power valves and vacuum brake backed out. Runs very well!!! Fun to drive.

Ol' Ron · 03-22-2023, 01:03 PM

This is very easy after you do it several times. Measure the clearance above the valves when they are opem. Add .050" this is measured fron the deck. Now measure the deoth of the valve pocket. Subtract the previous number that plus the thickness of the head gasket is tha amount of material you need to remove. Don't remove more than .070" forgot why. Place the head in the mill. If a broach just shim the side you want to mill off, Chamber size wil be reduced by aprox 10 CC (Depends on original heads. Not recommended for Late heads, very thin at the top).
I may have missed something here, but somebody will probably catch it and correct me, I hope
Gramps

Scott McDermott · 03-22-2023, 01:45 PM

Thanks everyone. Good info. I should have some free time to play around with it this weekend.

Ol' Ron · 03-22-2023, 04:26 PM

I think the .070" max was due to spark plug interference. Not sure. I\ve been working on a simple way to move the plugs, but not there yet?????

ronn · 03-23-2023, 10:19 AM

use jet fuel..........

40 Deluxe · 03-23-2023, 02:21 PM

Quote:

Originally Posted by ronn

use jet fuel..........

....which will give you a smoking under-powered slug (if you could even get it started!).

40 Deluxe · 03-23-2023, 02:25 PM

Quote:

Originally Posted by Ol' Ron

This is very easy after you do it several times. Measure the clearance above the valves when they are opem. Add .050" this is measured fron the deck. Now measure the deoth of the valve pocket. Subtract the previous number that plus the thickness of the head gasket is tha amount of material you need to remove. Don't remove more than .070" forgot why. Place the head in the mill. If a broach just shim the side you want to mill off, Chamber size wil be reduced by aprox 10 CC (Depends on original heads. Not recommended for Late heads, very thin at the top).
I may have missed something here, but somebody will probably catch it and correct me, I hope
Gramps

Ron, When angle milling, The head bolt holes will no longer align with the block. Do you redrill the bolt holes at the new angle, and do you spot face around the bolt holes for the new angle?

Ol' Ron · 03-24-2023, 07:47 AM

The angle is so slight that I never gave it a thought. Probably the right thing to do, BUT???

G

OH! you might want to check piston to head clearance. You might have to Dermmel alittle clearance.

03-22-2023, 06:39 AM	#1
Scott McDermott Junior Member Join Date: Aug 2020 Posts: 7	How to Increase compression on 1937 Flathead I need to rebuild my 37 FH. If possible, I'd like to bump up the compression, but I'm not finding any options for piston/heads to do so. I am aware of the Sharp heads, but $1500 is a bit steep. Are there any other options or should I just build back original?

03-22-2023, 07:18 AM	#2
Bored&Stroked Senior Member Join Date: Jan 2011 Location: Central Ohio Posts: 5,906	Re: How to Increase compression on 1937 Flathead Without spending too much money, you can check the compression height above the pistons and if it is over .045, then have the heads milled to bring the clearances down to .040 to .050. Flatheads like a tight squish area. Other than making extensive changes to increase the cubic inches (stroker crank of some sort) or doing additional modifications to the heads (filling in the transfer area), there are no other easy and inexpensive ways to go about it. Other performance things to consider are a mild CAM, improved ignition curve (mods to the distributor), new intake and dual carbs and exhaust.

03-22-2023, 07:19 AM	#3
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,985	Re: How to Increase compression on 1937 Flathead Angle mill the stock heads.

03-22-2023, 08:12 AM	#4
Scott McDermott Junior Member Join Date: Aug 2020 Posts: 7	Re: How to Increase compression on 1937 Flathead Thanks B&S and Ol' Ron. I probably should have written a little more in my original post. I planned on two 97's along with a Isky Max-1 Cam and recurve dizzy. I've previously changed over to Pertoronix 12V and built a 2" dual exhaust. When I couldn't find head/piston options I was concerned the cam and carbs would be of little value if the compression wasn't increased. Any idea what a ballpark CR would be after milling the heads?

03-22-2023, 12:09 PM	#6
Bill OH Senior Member Join Date: May 2010 Posts: 454	Re: How to Increase compression on 1937 Flathead Sponsored Links (Register now to hide all advertisements) I have a 221 +.030, dual 97s, Max 1 cam, pockets milled into the heads for the valves, dual exhaust, timing marks by the hard stop method, 45 main jets , 71 power valves and vacuum brake backed out. Runs very well!!! Fun to drive.

03-22-2023, 01:03 PM	#7
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,985	Re: How to Increase compression on 1937 Flathead This is very easy after you do it several times. Measure the clearance above the valves when they are opem. Add .050" this is measured fron the deck. Now measure the deoth of the valve pocket. Subtract the previous number that plus the thickness of the head gasket is tha amount of material you need to remove. Don't remove more than .070" forgot why. Place the head in the mill. If a broach just shim the side you want to mill off, Chamber size wil be reduced by aprox 10 CC (Depends on original heads. Not recommended for Late heads, very thin at the top). I may have missed something here, but somebody will probably catch it and correct me, I hope Gramps

03-22-2023, 01:45 PM	#8
Scott McDermott Junior Member Join Date: Aug 2020 Posts: 7	Re: How to Increase compression on 1937 Flathead Thanks everyone. Good info. I should have some free time to play around with it this weekend.

03-22-2023, 04:26 PM	#9
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,985	Re: How to Increase compression on 1937 Flathead I think the .070" max was due to spark plug interference. Not sure. I\ve been working on a simple way to move the plugs, but not there yet?????

03-23-2023, 10:19 AM	#10
ronn Senior Member Join Date: Feb 2011 Location: NNNNNNNNJJJJJJJJJJ Posts: 7,873	Re: How to Increase compression on 1937 Flathead use jet fuel..........

03-24-2023, 07:47 AM	#13
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,985	Re: How to Increase compression on 1937 Flathead The angle is so slight that I never gave it a thought. Probably the right thing to do, BUT??? G OH! you might want to check piston to head clearance. You might have to Dermmel alittle clearance.