head mods ??????

aussie merc

aussie merc

Well-known member
some would say that this belongs to HAMB or Jalopy journal but has anyone found or heard of a way to fill combustion chambers on iron heads to reduce the CC and more important did it work and for how long.
 
I use foil balls to to get the actual dimension above the piston, have them milled to bring them (a little too) close, and then check them again and use a die grinder to bring everything to where I want it.

I will admit that I have not done this with stock iron heads, but I have done 3 sets of aluminum heads and it worked well.
 
Assuming you are seeking to raise cylinder pressure, the accepted method is to have the
heads resurfaced a reasonable amount. Then, place modeling clay in the area above the valves, put on the head gasket, secure the head to the block and turn the engine over.
Remove the head and determine if the piston and valves have acceptable clearance. Modifying the combustion chamber is not a good idea as the conformation alteration can affect the combustion pattern, and risks breaching the coolant part of the head.
 
supereal said:
Assuming you are seeking to raise cylinder pressure, the accepted method is to have the
heads resurfaced a reasonable amount. Then, place modeling clay in the area above the valves, put on the head gasket, secure the head to the block and turn the engine over.
Remove the head and determine if the piston and valves have acceptable clearance. Modifying the combustion chamber is not a good idea as the conformation alteration can affect the combustion pattern, and risks breaching the coolant part of the head.
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I believe its is better to "measure first, then cut". Every set of heads I have done needed a different amount removed from each head to get them close. This will minimize the amount of clearancing need to be done to get the final fit. You will thank me, especially when doing stock iron heads.
 
aussie merc said:
some would say that this belongs to HAMB or Jalopy journal but has anyone found or heard of a way to fill combustion chambers on iron heads to reduce the CC and more important did it work and for how long.
Click to expand...


The only way would be by building up using weld there is a good rod available for Tig welding cast iron but its expensive. Check out our cast iron welding on YouTube to find the welding rod. There's no other material that would hold up under the compression and heat cycle {epoxy's} other than welding.
My findings have shown to me at least opening up the combustion chamber actually {thus increasing breathing} improved the final results.
Ronnieroadster
 
Yes, A properly modified iron head is much better than most aftermarket brand. After doing the usual things like milling for the proper clearances, it's then time to fil in the areas with bronze material to increase the CR, and requires a good wood stove.
Grrab a stock 59A head off the junk pile ands clean it up and check for cracks, place on wood stove over night and keep a good fire going, head should get to 800/1000 degrees. Then using a dir. grimmer with a coarse stone in it rough up the area under the exhaust valve, then fill this area with bronze. Let cool slowly to prevent cracking. Now you can dot he milling
The one advantage this has over the after market heads is: The transfer area is better. At Dan bury when the restrictions for using after market heads was lifted, many of us went to them, but after a few races went back to the modified iron ones. Live and learn
Gramps
 
yes its out there but can be done thanks to all who replied the general advice is what i was thinking and since the AU dollar nose dived and freight costs have gone lunar it is becoming a viable prospect as a set of alloys with studs and gaskets will now set someone back around $4000 AUD
 
I have welded many sets of aluminum heads to convert to flat top pistons and close the transfer area down.
Iron heads could be done the same way by TIG welding if there was a need.
 
They didn't have those modern methods of welding back then, However reducing the area of the transfer area will raise the CR but reduce flow at hi RPMs. At least thats what I found out????
G
 
Jus came in from the shop, working on an intake. I was thinking of our discussion on heads. I have a great deal of respect for Pete. He's from the old days and we learned things about the same way, watched what others did, and take advice from the right people. but most of all we learned by our mistakes. Our biggest differance is: we raced under different set of rules, the application was different , what worked for me might not work for him and vice s versa. However, you must consider the fact that the only thing that makes Horsepower is air, or the oxygen it contains. Since I've been on the barn I\ve learned allot. I try to pass along as much as I can.
Gramps
 
Ol' Ron said:
Our biggest differance is: we raced under different set of rules, the application was different , what worked for me might not work for him and vice s versa.
Gramps
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Very true. The only rules we have are, the block has to be 53 or older, no blowers or nitro.

On the transfer area, if you lower the transfer area in the head and deepen the relief in the block, you can end up with the same volume flow and a shorter path to the cylinder. That alone was good for one tenth of a second on a quarter mile dirt track.
 
Well, I'm going to get practical here. First of all, I am not doing any racing these days, (although I used to). I just wanted the most efficient street engine I can make without breaking the bank. Using the technique outlined in post #3 above, I strive for a quench of .045-.050" over the piston top with a consistent combustion chamber volume. After a reasonable break-in period, the last engine I built (a 258" with a MAX-1 cam and tweaked Edmunds heads) yielded 150 psi on a compression test (versus the factory specification of 110 psi). I don't know what the actual compression ratio is, but the engine runs strong and performs very well. I am completely satisfied with it.

I quit chasing that tenth of a second a loooong time ago.
 
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Very good, our max displacement was 258 CI and with a 400jr and head mods we got 169/165 PSi Not sure of the accury of the measurements but that came out to be apeox 8.7Cr. I built a 258 Hydro engine with a similar head but bigger ports and valves and it was clocked at 62 mph on 66 recors using a Lycoming engine. Not bad for a flathead!!
 
The engine in my '36 is a 59AB that was built the first time in 1954 by a speed shop in SLC. The spec's were .40 overbore. Weber F1 cam, Offy heads, Offy Super dual manifold with 97 carbs, 12 pound aluminum flywheel and Harmon-Collins ignition, stock '36 manifolds with dual Douglas mufflers.
I used the car for daily driving to work, etc., and occasional street/strip drag racing. The engine ran very well until 1958 when it broke a piston, doing some serious damage to one cylinder.
I did a lot of research looking for someone to rebuild the engine, finally found a machine shop that specialized in performance engines for the stock car racers.
The block was savable by boring the damaged cylinder out to .60 over and sleaving it, then boring the other cylinders to .60 over size. The shop did not like the Offy heads, they preferred to make their own performance heads by using a procedure called, Milling, doming and Fly-cutting stock heads.. A stock flywheel was milled down to 15 pounds, all of the remaining accessories, carbs, ignition, etc., were used.

I really have no idea what the Milling, Doming, Fly-cutting of the heads involves.

The engine has ran very well since 1959, with nothing more than normal maintenance.
 
Those little engines do run well, I like to got 125 over that gves one point in Cr and 20 cubes. win/win for the little stocker.
g
 
The crowd I ran with when I was younger liked engines for street use that were not to radical, The Weber F-1 or Howard M8 did not have to much over-lap so the idle was very civilized with just enough overlap to let people know the engine was not stock.
The original Offy heads were somewhere around 10/1 as I recall, Had to use nothing but premium fuel. The modified heads were much better.
 
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