Well, I finally pulled the head and what I thought was a sticking valve was the right rear piston hitting the head. Not enough, I hope, to bend a rod, but enough that you can see marks on the piston top and on the corresponding part of the head. On the front cylinder on the same bank, the valve was hitting the spark plug electrode -- enough to close the gap significantly. The heads were some original pre 48 Edelbrock "block letter" heads. When I gave them to the builder, I told him to check them, use them if they were good, but to let me know if they were bad so I could buy some replacements. I guess he didn't check that well. I'm assuming they were milled too many times during their 60 year life. I pulled the other head to check everything out. It doesn't look like anything is hitting on the left side, but at TDC all the pistons, on both the right and left banks, extend above the deck by about .020. The pistons are domed, so the top of the piston is even higher above the deck than the .020. Is this correct? Should the pistons be above the deck this much (or even at all) at TDC? I'm thinking of replacing the Edelbrocks with a set of Navarro heads. Will I have enough clearance for the pistons and the valves without relieving the heads? Does the entire engine need to come apart because of the piston height at TDC? The cost of any fix is going to be on me. I can't take the motor back to the builder. As I mentioned, it was built about 8 years ago and it sat while I fixed up a house and started a family. It was only recently I was able to get the engine in the car, wired and running, so it's too late to go back to the builder. Thoughts?
Anyone else have any advice? I'm really unsure what to do next -- bolt on a new set of heads and hope for the best or tear down the engine and start all over again. I'm primarily concerned about the piston height. Should they be that high above the deck or even above the deck at all?
As long as the rings arent popping out of the cylinder it should be fine, use a thicker head gasket and drive the fuck on! Don't over complicate things, its a flathead, not a formula 1 motor.
As long as the top ring isn't popping out of the cylinder, you should be OK. Just tell everybody you have "pop up" pistons. You could probably have the Edelbrocks redomed a bit and use them. I'd be surprised if they needed much to clear. Should be OK after that. And get shorter plugs. I used to use Champion H10, but tried some NGK which I heard were the new trick thing. Until my valves pounded half of them flat. Back to the Champions.
Why is it only hitting in one cylinder? Is the deck uneven? Uneven head surface? Or is that piston different? You need to do some measuring to find out what's going on there before proceeding with a solution. As mentioned, a thicker headgasket might be the ticket. or alittle bit of clearancing with a die grinder might take care of it.
You might put a post on fordbarn.com for Old Ron. I think he fly cuts heads with a special cutter he has. Roll up a ball of tin foil for each of the 8 cylinders and place on the pistons, put the heads back on without gaskets. Then roll the motor over a couple of time, remove the heads and measure the thickness of the foil. If you can redome it's prolly cheaper than spending $500-$600 for another set of Edelbrock or Offie heads.
Give us the whole picture. What do head domes look like, how big is remaining diameter of dome area?? How thick are gaskets?? How much piston protrusion?? Typical flathead clearance is about the same as typical headgasket thickness. You may have multiple problems...need to study all the details before making a move on this. Slight recontouring or a thicker gasket may save the heads, but maybe they are not the problem.
For clearance checking use modeling clay.Place a thin layer over the area to be checked and wipe the head surface with a bit of oil so the clay will release. Cut through the thin areas with a razor blade to check how much clearance you have What is the bore/stroke on this engine? One time I had a 4&1/8 stroker engine and the pistons were for a 4 inch stroke,other than needing big bore gaskets worked fine for years. just a bit more compression.
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