Hey guys I have a quick question. I'm rebuilding my 88 454 mag because got a stuck valve and hit a piston. The piston is ok just a bent valve. I'm looking to upgrade a little. I'm debating getting a power pack from Mkhammer.com which comes with a imco thumper exhaust system, dui distributer, box and wires. But idk how big of a cam I can put with that exhaust without reversion. Or spend the money and get harden marine low exit exhaust kit. The power pack is 1800 and the low exit is 2500. What is the best for someone not trying to break the bank.

Probably wouldn't go much bigger than 454/420 hp cam as far as off the shelve cams any way.

I was thinking 235 245 would be good but I think I need an aftermarket exhaust.

Check exhaust manifolds for water leaks. Slow leaks can cause the valve stems to corrode and hang up causing PTV contact.