That what my set-up is now and the thundbolt 1V that I'm using has no rev limiter. What do you estimate the HP would be with my set-up.I would like to get more HP out of it and still run without a blower or super charger. Thanks Alec

After some quick calculations, I came up with a compression ratio of 8.39 to 1 assuming the block was not decked and the pistons are .020 in the hole, Fel Pro gaskets .042 thick and 3 cc valve reliefs in the pistons. The good news is, this would make a great engine to put a blower on. The cam is advertised by Crane to be a good blower cam also. Or you can burn any kind of cheap gas you want. Unfortunately this comp. ratio is going to limit your options n/a. Going to a larger cam or retarding your cam will just cause you to lose more cylinder pressure and torque.

You said stock mpi ignition (which has a rev limit of 5050) and TB IV w/o rev limit. Which is it?

I have a thunderbolt 1V without a rev limiter. I had the mpi 502 dist in the carb engine and ran it for one season changed it out when I rebuilt the engine . The 502 mpi has a rev limiter but its built in the ECU not the dist. I replaced the MPI with a carb set up.

Before vs after
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ZZ502 cam vs 731
Stock rect heads vs Iron Eagle 308's
stock compression vs less compression ????
Same intake/carb/exhaust

x vs 100hp more ? Don't think so !

What is the piston part# so we can get a close guestimate on compression ?

So far, I have a sneaking suspicion that your 2nd set of mods wherent enough over your 1st set of mods to really gain you anything much.

If your compression works out to 8.75:1 or greater, next time a round I'd run a good single plane intake and a different cam....if looking to go faster.

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BTW: I didn't see if you answered the fuel system questions I asked and what you are running for total timing. If you have, please excuse me.

If you did not run it on a dyno you have know idea what you have ! You might have all the best parts in the world but if they are not set up right you may end up with less HP than what you started with. Forget about what THEY tell you , spend the money and put it on a dyno so you know what you realy have . Or you can spend the next two years chasing your tail ! :ernaehrung004:

And the 121 cc chamber in the heads.

Call Rm builder tell him what you have and he will make you a cam shaft that will make you power. That would be the cheapest way to go. :grinser010:

I doubt its the cam. Its probably the 121cc heads and low CR. The carb and intake are fine as well.

If the compression were higher, say 9.7 or so, I'd recommend going to the 741 cam and a Dart single plane. I'm afraid in this case they will just kill torque. Assuming there is no rev limiter, a small supercharger would be the easiest way to fix this. Otherwise complete disassembly, small dome pistons, deck the block. Do the math to get a real C.R. It may also require milling the heads and thinner head gaskets. My 548's with small dome pistons and decked blocks only came to 10.0 to 1 and I'm compressing almost 10 percent more into the same size space.