Cold Sweat, as an economical upgrade, I've had great luck with the 496 exhaust. The only thing I would suggest is extending the inner tube, in order to prevent the reversion issue mentioned earlier.

The 420 runs a fairly "radical" cam in order to generate its horsepower from a flat-tappet cam. Thats why the tubes are so long off the back of the risers.

Nick

Are you talking about the aluminum or the cast? Will they bolt up and clear ok? Was thinking along the lines of the 500hp gils with the higher tails. I've seen a few sets for sale, but wasn't in the market at the time. I think my old exhaust flows well, but those rubber gaskets they used caused alot of problems 20 years ago and they are HEAVY. Thanks for the reply

O man are they heavy or what! one complete system for a single engine is 174 lbs!!! And then if you have 2" riser extensions, add an extra 12 lbs X 2! The last 420 refresh I did involved stroker cranks to make them 496 cid. In order to meet the budget on the build, we bought two sets of aluminum 496 raw water manifolds. We also upped the compression a litte and upgraded to Dart heads and HP 500 intakes. We also changed to a different camshaft. The package worked well and produced a little over 550 HP. The aluminum exhaust took about 200 lbs out of the back of the boat too!

Or if you don't want to deal with the exhaust now, just swap out the cams(which may needed to be done anyway) to a good performance cam that will work with your exhaust...Rob

I ran stock Merc exhaust on 420's for a couple seasons until I could afford to upgrade. No problems with reversion.

Hey P can I get your Email address? I`m interested in your engines. Sorry for the thread interuption.

EXCELLENT!

Thanks for the response, I am in the process of looking at headers, but Man, are they going to break the bank. :rolleyes:


Thanks again,

Phil

Interested?

philsnyder(at)mris.com

These need to go if you guys know anyone that is interested.

Sorry to piggyback on your thread.

http://www.offshoreonly.com/forums/s...d-engines.html

Are they for trs or bravo?

Also, how many horse are the HP500's? Are they actually 500, or is that measurement at the prop? sorry for the ignorance