TorchLK

I have read that same thing from searching. A lot of people say the stock manifolds work just fine. I'm having a hard time buying into it with a well-built Whipple motor... especially if I decide to add a little more boost.

I'm definitely interested in hearing more opinions.

EDIT: I believe I do have the stock aluminum manifolds. I will check for sure tonight.

SB

Full Throttle Marine (FtmBob) has done tons of N/A and S/C 496 (8.1) builds, dyno tests, and installations. He has a engine and propshaft dyno. Best thing, he reported most of the results here. try doin a search..it will be worth it. He comes on here once in a while, but since his retirement a few years ago, not that often. May try google instead of OSO's search function as OSO's search really kind of sucks.

Edit in: some tests included different exhaust systems during same dyno tests.

bobl

Someone mention my name??? I never did any exhaust comparisons on a Whipple supercharged 496. I built a few but they all had aftermarket exhaust. Forged rotating assemblies, custom cam and stock heads made right at 650 HP best I can remember. I probably have the dyno results buried on a computer somewhere if there's any interest. I would say at that HP level a good exhaust would be worth doing.

Bob

SB

Nope. cause I called you by the wrong name.

Drock78

I know of a pair of fully built and forged procharged 496's making around 750hp and running Dana Marine exhaust if I remember correctly.

offshorexcursion

The Marine world is Delusional by neglecting exhaust so often, it is a very important part of a properly packaged engine combination that when designed correctly will improve power and reliability.

Unfortunately the majority of builds and advice shared on this site utilized "dyno headers" NOT the actual marine exhaust they run when making a pull, spreading misinformation.

Don't get me wrong, exhaust is expensive, and not always the best bang for the buck for every build, especially when trying to to design one specifically for your engine.

Tell us more about your build!?

OP keep on with your research selecting an upgraded exhaust.

TorchLK

I have noticed the fact that a lot of marine builds seem to neglect exhaust. I know that car engines and marine engines can be quite different but I am very familiar with engine setup. (Last car I had was a 1200RWHP LSx turbo motor)

However, I don't have much experience at all when it comes to wet exhaust and the characteristics of it. From reading it seems like any wet exhaust doesnt perform that great compared to full dry.

The engine setup is as follows: It isn't anything extreme but a solid build making some decent power and built for reliability.

-496 8.1L based (slight overbore) approx 500 c.i.d
-Diamond custom pistons (lowered top ring land for boost, etc.) (very nice set of Total Seal Rings at normal size, not bastard 8.1L size) (tool steel pins) (skirts coated by Line2Line)
-Callies forged rods (slightly shorter than stock in effort to stay out of oil ring on pistons)
-Forged crank
-ARP head studs for 8.1L
-Cometic MLS head gaskets
-Whipple 2.3 blower on 5-6psi (with intercooler) (may up the boost a bit at some point)
-Stock iron heads, mild clean up work, nice valve job, pac springs with more spring pressure for boost, inconel Manley exhaust valves, Manley intake valves
-Comp roller rockers
-Trend pushrods
-Holley Billet 12-1200 fuel pump with -8 braided line on entire fuel system
-Spinning a 34p BBlades labbed prop with some added cup
-Bravo 1x built by Max Machine Worx

That should sum up the basics. It's not anything crazy but it makes good power for what it is.

bobl

All the testing I did was in full marine trim with wet exhaust.

Torch-what cam are you running?

TorchLK

Yes, your test was the most valid I have seen due to the fact that it was all thru wet exhaust.

I have the stock 496 HO cam. I kept this cam at the time cause I dont really have a way to tune the boat other than just a mail order tune (like from Whipple). I wasn't sure how accurate of a tune I could get for a cam change. I can't find anyone local who tunes the Motorola 555 or even had the software. I just felt more comfortable keeping the stock cam for this reason.

I would love to change the cam and add a real efi system like a Holley dominator or a big stuff 3

bobl

Whipple did the tunes on the builds I did. They should have a good tune even with a cam change. Don't have anyone else tune the ecu, as they have perfected it for their supercharger application. There are a couple of people running the Holley HP systems on 496's, so it can be done.