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?

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.

Re: How to Increase compression on 1937 Flathead
 

Angle mill the stock heads.

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?

Re: How to Increase compression on 1937 Flathead
 

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.)

Re: How to Increase compression on 1937 Flathead
 

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.

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

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.

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?????

Re: How to Increase compression on 1937 Flathead
 

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

Re: How to Increase compression on 1937 Flathead
 

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

Re: How to Increase compression on 1937 Flathead
 

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?

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.