Rick252

Would I be better to purchase a crate motor or completely re-build my now stock 454 MPI. When I say completely I mean starting with replacing the weak crankshaft and going from there. Thanks for any tips you can provide.

Mr Gadgets

One thing to look into is a 502 short block and then add some after market heads.. You can come up with a good motor that way. But it all depends on price. The crate motor shouldnt have any "engine builder" issues and it has a lot of quality pieces. They do a good job building them. I had an issue with piston to wall clearance, but I had a roller cam and Merlin heads and ran it hard. So more power is more heat and I should have had the piston to wall clearance opened up a couple of thousanths..

Good luck with your project.

Dick

Vinny P

To get a fair answer to your question I have to ask how fast do you want to go? And of course how deep are your pockets?? GM crate motors are good motors but are not set up for marine use. First and foremost the cam profile is wrong, along with some of the clearances inside the motor. It is however a good base to start with, but I feel it should be gone through before dropping it in a boat. It can work real well with a little work.

Rick252

I just read an interesting article in Family/Performance boating mag. It said that the 7.4/330hp is not the junk its made out to be. The cranks are cast but GM has used them in several high performance applications. Also contrary to belief it has 4-bolt mains instead of the 2-bolt that most people think.. With a few minor changes such as cam and heads you can get a reliable engine with approximately 425hp. As I read this I noticed that the engines were carbed. Mine is an MPI. Would this make a difference? I'm not looking to blow the water apart. If I could reach 70mph I'd be happy, for now anyway

jdnca1

There are many 2 bolts with cast cranks 427's out there putting out a reliable 450-500hp in vintage Vette's.....

Budman

Hey JDNAC1,

Sounds like you might know your Vette's. My friend just bought a '67 with the 427 tri-power option - the 400 HP one, not the 435. I think those came with oval port heads and a hyd cam instead of solid. He recently tore down the motor and found that someone had replaced the closed chamber heads with a set of later model open chamber heads, probably in an effort to lower the CR. He also found that it has a cast crank in it. It is the original block. My question - is it possible that this cast crank is the original crank for this engine? My friend thinks that it was replaced when the heads were switched out, but I think that it might be original. Your statement kind of backs up my thoughts. Do you know of any of those cast-crank 427's that were original?

Thanks!