1972 Demon 340 engine mods

I ran some numbers with the later, low compression 340 pistons, and even with a .028" thick head gasket, and the 63 cc chambers in the 60779 Edelbrocks, the engine is still going to be in the low 8.3-8.5 range for static CR. That is not high CR, and you're gonna have to stay small on the cam to avoid dumping the low end torque into the toilet. That is where the issue with a solid is going to crop up..... finding a short duration solid that will not dump the dynamic CR too low is a challenge. Finding a hydraulic is easier.

I'd be looking at something like the 2 smallest VooDoo hydraulic flat tappet cams, or similar, and not be afraid to put the ICL at 106 or even 104 degrees, to help keep the low end torque good. Stepping up through the gears with that 3 speed is gonna need low RPM torque unless you want to wind it way up in RPM's before each upshift. Using the smallest VooDoo hydraulic flat tappet cam and installing at an ICL of 106 would put the DCR in the low 7's..... that is not a high DCR for the street but you are not going to do much better with those pistons.

Looking at a hydraulic roller like the smallest VooDoo Retro-fit hydraulic roller is interesting. You can keep the duration down and get considerably more lift to help high RPM breathing and HP. It would try that before looking at a solid flat tappet. But it is still dropping the DCR below 7.

I would seriously be tempted to mill the new Edelbrocks about .030" to get about 5 more cc's out of the chambers. Then you would get the DCR up to the mid-7 range. You could mill even more off, and then the cam possibilities open up even more.

By the way, I see you are in the Warsaw.... it is great to hear from owners outside of the US and Canada.