Offshoreonly.com - thinking about LS swap from twin 454???

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- General Q & A (https://www.offshoreonly.com/forums/general-q-20/)

- - thinking about LS swap from twin 454??? (https://www.offshoreonly.com/forums/general-q/357393-thinking-about-ls-swap-twin-454-a.html)

Were your old cams making less torque at the wot rpm than the new cams?

Quote:

Originally Posted by MILD THUNDER (Post 4656429)

Were your old cams making less torque at the wot rpm than the new cams?

Can't honestly answer that haven't dyno'd the latest combination, but I believe so. Dyno sheet says 559@5250 and 477@6500 on old setup. I'm propped to 5400 currently on my latest setup. I went from best speeds; 79-80 to 82 from the different setups.

Quote:

Originally Posted by SB (Post 4656365)

I mentioned KEM's many times many years ago. They where like $700-800 back then, Sure they are more than 1k now,but have not checked in a few years. Give'm a call.

I looked for KEM LS manifold and not seeing any. Happen to have a link.

Quote:

Originally Posted by compedgemarine (Post 4656415)

you just have to use the right correction factor and they make all you want.

and if u paint it blue hell ya never know!!

Quote:

Originally Posted by Alwhite00 (Post 4656438)

I looked for KEM LS manifold and not seeing any. Happen to have a link.

Sure thing. :drink:
KEM Equipment, Inc.

Quote:

Originally Posted by Alwhite00 (Post 4656438)

I looked for KEM LS manifold and not seeing any. Happen to have a link.

Chevrolet LS Kodiak Exhaust Manifold and Riser Kits

Quote:

Originally Posted by Rookie (Post 4656437)

im curious if the dyno numbers were done in full marine trim with the SM exhaust or done in dyno trim with dyno headers. I’d guess it was at least dyno headers and I think therein lies the problem. The SM exhaust will not act the same as a long tube dyno header causing the power to fall off quickly and dramatically. Whereas the second combo requires a lot less from the exhaust hence you get more usable power from it.

ExtremeCFM, with your 5 posts here its sounds like your engine(power) knowledgeable. While there may be an example or 2 of making the kind of power you want with 454's its not common and again maybe there is an odd ball out there, but in general that amount of power from a NA454 will not be user friendly. Also what outdrives are you putting with these motors? Even if you can reliably make that power...say goodbye to your bravos or TRSs.

In short, I say build the 454's to 550hp and let them eat.

My personnel experience, I had a pair of 509ci 650hp(in dyno trim) engines in a 32 Sunsation. They were built right, ran awesome and lasted over 10 years, but. Honestly, yeah it was fun to blast up to 90 or so with the bigger power but, it was a pain in the ass other wise. Had to run high test, 900cfm holleys drank fuel, was a pain to dock because of idle characteristics(possible reversion) etc...etc. The boat had 496 ho's from the factory and was perfect.

Quote:

Originally Posted by jadento (Post 4656499)

what kind of top speeds were you getting with the 650s compared to stock 496's?