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According to Raylar who has more 496 experience than most, something over 525hp http://www.offshoreonly.com/forums/g...ml#post1580344
They sure work well for my 450 hp build, and you can't beat the $ value - I paid $350 shipped for 20 hours takeoffs from the swap shop. |
Originally Posted by Budman II
(Post 4280523)
Not sure if the 496 manifolds make much of an improvement on performance, but the fact that they went to a dry riser / manifold joint should make them less prone to internal leakage and more reliable. Thousands of engines have been ruined when the stock Merc wet joint manifolds start leaking water back into the engine internally. Hot exhaust valves definitely do not like being quenched with cold lake water!
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The 496 risers have a smoother bend and larger inside then cast.
Risers are SS so you can have them cut and shortened or lengthened if needed. Dry joints. Aluminum ...lighter by 36lbs a manifold. Risers.... stainless, don't rot and lighter then cast by about 10 lbs each Exhaust runners/dividers are built into manifold (cast are just open inside) They are smaller over all and not as bulky as the cast. Fits most BBC. I have them on 3 Gen V 454's and a Mark IV 454/496 stroker now. Easy to drain with a plastic wingnut on the fill elbow And I could go on and on over the benefit over stock exhaust but I hate doing it. I started buying them as new take-offs years ago. People would buy a brand new boat and take them off and buy new then sell them for nothing. The deal is, is this. They are a great midgrade exhaust system. Not a super set from a famous builder but if Merc could have picked up any HP by casting it better they would have. IMHO a lot of us have exhaust systems we should never have. 5 grand in exhaust on a $5 grand motor. Crazy. |
Merc looks to be using the 496 setup on the newer HP 520. Check out the dyno sheets Full Throttle Marine did on the 496 exhaust vs Dana Marine. The Dana setup was only worth 16 hp over the 496 w turbulators removed at peak hp. Thru the curve they were dead even until the mid 4k range. If you can find the alum editions there is a nice 70lb weight savings.
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Originally Posted by dereknkathy
(Post 4280580)
Wasnt that gil manifold also used on 454-420 hp engines? Anybody know how much power they support?
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So when do the 496 manifolds start to choke ?
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Sorry ! I now see where this was discussed !
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It looks like the Isky 270/280 mega cam will be a good choice for my build. (454 mag stock) This is a .542 int./.565 ex., dur. @ .05 - 221int./232ex. 114 lsa. I think this should allow me to run the stock exhaust now and upgrade later to the 496 manifolds. This is probably as big a cam as I would want for my boat from what I understand. Another option is this comp marine extreme cam, .544int/.547ex., dur,@.050 is 226int./236ex., 112 lsa. Another option, Howards cams .527int./.533ex., [email protected] is 225/235, 114 lsa. What do you think ?
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I run the ISKY MEGA 270/280-114. Ran fine with stock manifolds. The 496 manifolds allowed it to rev a couple hundred more after tuning. It's a great cam for a mild build.
If I was to do it over again, I'd put the 496 manifolds on and run the ISKY 280/290 mega or a similar Crane. Make sure to run the ISKY lifters and springs to go with their cam. ISKY's stuff is high quality, never had one go flat - proper break in and it will run a long time. |
How about some "made in china" headers? Anyone on here ever use these?
http://i1283.photobucket.com/albums/...psse3vw0ah.jpg |
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