I think he said he was running aviation fuel in some percentage. We would need to know the cc of the heads to know if the domes were too much. I run -12cc pistons with blowers.

I think I need flat top pistons as well. Sucks the engines were just assembled. THis is a lesson learned from appliying car engine know how to marine application, two different worlds. I can run aviation gas 50% or 100% since its $4 gal. but this is not practical in the marine world. Problem is I have 2 engines that will have to be torn down. Piston dome is -17cc

I think you can make them live as is, you will just need to tune appropriately. Richer 12afr, less timing 31-32 and make sure the cylinder heads stay cool as possible. Alum heads would also be a benefit if you do not already run them. What is the current comp ratio?

Those look like little domes for closed chamber heads. I believe those run with open chamber heads give you around 10.5:1 compression. With the right tune up you should be able to work with that with 93 octane.

more pics. Heads have gone to the machine shop that installed the valve seats.

That one piston is gone, bummer. How does the cylinder wall look?

on another note, i would like to thank all of you for your valuable opinions and insight. all of the information and commentaries have been helpfull and educational for the future. hopefully I can get this engine toghether, tuned right and running smooth.''

again, Thanks

cylinder is scratched, will need honing or a jacket maybe. The carp in the cylinder is the residue from the valve seat

check fuel pressure, low pressure and or volume can lean a motor which will get the combustion chamber so hot the valve seats will fall out.
I had a carb float stick which caused needle to stay closed, motor was then only recieving half the fuel from the other side of the carb. pop! my engine looked exactly the same

Did the valve seats drop out or get beat into the head?