Hi,i would like to change my engines:2x330hp 7.4 v8 mercruiser that stay on magnum marine27 starfire.....and i would like put on about 420 hp for engine and take it around 450/470hp with the exhaust system!!!1
But i'm very uncertain for the choice of the model ,could you give me some advice?Remember that i love the rumbling!!!
Thank's federico.

If you buy new 496's, they are closed cooled and run off of 87 octane fuel.

You can do it with either, but the 502 has better internals. The 502 is also a better starting point if you want to make more HP. The 496HO is a solid package if you stay conservative. It really depends on your specific needs and goals.

Thank's zt260 for the answer,i 've got a magnum 27 and put on it more than about 450 hp... it would very dangerous(also because i run in the Mediterrean sea and it isn't very calm)!!!so i woud put a max between 420/470 hp for engines and not more...and i want a big big sound,like a thunder!!with these specifics needs what do you advice me??
bye,federico

A closed cooled 496HO with CMI's 496 headers would do the job and put out over 450HP. It will be rather loud without mufflers, but that's what you want. Good Luck.

I'd go with a couple of 400HP stroker small blocks. Big blocks in a 27' Mag is azz heavy, I know the 28' Cig is better with SBCs.

Do the exhaust outlets come out the same place on the 496HO's as the 454/502's?

The new 496 is a little wider.

Thank's to: zt260,Unsane,Pat Mc Pherson for the advices.....I think that i'll oriented to put the 496ho with CMI exhaust!!!As soon as i can i'll post the photo(i hope)!!!! Bye federico

I don't know US1 Fountain...i'm sorry.