Hello everyone, I bought an original '41 Ford stock 59A-B engine and want to hop it up a little bit. It is completely stock & supposedly rebuilt (a while ago). I recently purchased some original 75cc Edelbrock Finned Aluminum Cylinder Heads (stamped 75 on water neck)...and a Edmunds Custom 2x2 w/Chrome 97's. So my question is: How far would I have to mill my 75cc heads down (Safely) to get my compression around 9:1? They have never seen any machine work. I know if I can shave it down to 65cc, that will set me @ 8:1. Plus, does anyone know how far you can shave down heads & still be on a "Safe Side"? I am all new to flathead engines, & just want to do it the right way the first time. Thanks!
I'd clay the valves first off, and see how much clearance I had. That will give you a good starting point.
I talked to a machinist today, and he was also telling me to pull the cylinder head & use silly putty....then install the head back on....then turn the engine over....then pull the head to see how much clearance I'll have. That will determine how much clearance I will have...and let me know how much I can machine my heads. I would love to go buy a nice set of Navarro Racing Heads...but they are also $725...Which I don't have (I wish!) He also advised me that we can cut the heads down quite a bit. Pretty neat actually how people took stock iron heads back then and brazed them & resurface to get a high compression head. Well, thanks for the advice.
Fill the chambers with 65cc's of oil and see how much milling it will take. Is cutting the valve pockets doable with those heads?
Compression is not everything in a flathead . You will reach a point where it is detrimental to breathing. Pinging will also be an issue. Talk with an experienced flathead builder before going our on a limb. Just taking a radical cut and putting the heads back on a stock flattie does not sound like a good plan. If it's a 59A engine it's not a '41.
I don't think 75 is the head volume, and I am pretty sure Edelbrock did not stamp volume on heads. 75 would put you down into stock compression range on an unbored and unrelieved egine... I think that is 7.5, at the low end of the high compression flathead range. CC it, as the stamped compression is utterly meaningless unless you know how E figgered it, whether head was ever milled more, whether it included relief volume, and 900 other things. Also, figuring out what head CC gets you what demands a lot of info on your engine. It is not gonna CC at 75...
yup Bruce is right. ( I detect a pattern here... )Edelbrock marked their heads with a comp ratio for an otherwise stock engine often marked F 75 M 8 which means ford 7.5:1 Mercury 8:1 the merc figure being higher due to the longer stroke, so more compression using the same head.
Roll up a little ball of kitchen tinfoil, put it on top of one piston. Pull the head down to torque with the gasket you're going to use. Turn the engine over. Remove the head and measure your now-squished up piece of foil. Say for example it's 90thou thick. Deduct 50thou from that (your desirable piston the chamber roof clearance) and what you've got left is the amount you can safely mill the heads, in this example it would be 40thou.
Good advice from new zealand ! I did that on all my pistons, as there was a bit of variance, (about 5 thou) so used the smallest measurement as a guide for the milling. left to right will be different also probably..
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