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Thread: I need a recipe to get 500 HP out of my 400 SBC

  1. #1
    I have a stock bore 400 SBC that I would like to put in my jetboat with Dominator pump with "B" impellor. I would like a recipe for 500 HP. These are the parts I have for it already.
    I managed to obtain some 400 pistons that take a 5.7 rod. They are 12.5:1 forged TRW's. New in the box. The 5.7 rods are PINK rods from a 350 SBC Targetmaster 4 bolt main. I'm a little concerned if the crank will hold up. I'm also concerned that the only good heads I have for it are Camel Hump heads with really small 58 cc's last I checked. They have 2.02 intake 1.80 exhaust. I would like to run the VORTEC heads because they flow so good, but if the camel humps will do the job, I would rather use those. I'm just worried about that high compression. Oh yeah, the heads are already set up with the big springs and studs and have already been machined ready for use. Again, compression is scaring me. I would like a combo that can run on 93 octane with a booster if needed. I would also like to use the parts available if possible. Obviously cam choice is what I I build this thing for torque or horsepower? Any advice would be greatly appreciated.

  2. #2
    Head casting numbers, or, better, flow bench numbers from the actual heads?

  3. #3
    Cheap Thrills
    Geeezas , Will a 12.5:1 slug clear a 58cc chamber ? :idea:
    This combo is for a 383 so you should see slightly more with 400ci.
    Heads ~ AFR195cc (260cfm)
    Cam ~ Comp mec. roller XR274. 236/242 @ 0.050.D 0.564/0.570 Lift. 110*lobe on 1.6 roller rockers.
    Edelbrock Victor Jr. intake and a 750 DP Holley.
    Makes about 515hp@6,000 510lb-ft @ 4,400.
    Good Luck

  4. #4
    12.5 with those heads? Do you know what springs are in those heads? Cheap Thrills, are those cam specs with the 1.5 rockers or the 1.6? Sounds like a healthy combo

  5. #5
    Cheap Thrills
    12.5 with those heads? Do you know what springs are in those heads? Cheap Thrills, are those cam specs with the 1.5 rockers or the 1.6? Sounds like a healthy combo
    Yeah those 12.5:1 slugs in 58cc chambers just doesn't seem like a good idea to me either.
    The Rockers are 1.6 in that combo.

  6. #6
    I mean are the cam lift specs figured with 1.6? The larger rocker will add some lift...

  7. #7
    Sorry for the delay in getting more info about the parts I presently have. I was concerned about using those big pop-ups in such a small chamber !! Anyways, my weekend from work is about to start so I'll go in the shop and get the numbers off the heads. I'm thinking really about getting rid of those pistons and get some cheaper hyperteutectic (spelling:idea: ) pistons. The boat will probably never see nitrous. I would like this boat to be fast but not at the expense of blowers, nitrous or turbos. A tunnel ram just to give it a cool factor is what I'll probably do later on. I'll give up some more info on what I have tomm. Thanks guys for your input so far.

  8. #8
    Cheap Thrills
    I mean are the cam lift specs figured with 1.6? The larger rocker will add some lift...
    Cam Specs were with Factory 1.5 rockers.
    Took me a while to dig that up sorry for the delay.

  9. #9
    The camel hums are usually the 461 or 462 heads, the only difference is that the 461 heads do NOT have the accessory holes. These heads can flow as good or better than some Vortec heads with a little work. If that's what I got, that's what I would run.
    I personally would just use a flat top piston with the 400 on 58cc heads. Better squish, predictable combustion and timing. And you would still be up there in compression ratio.
    This part may start an argument: I would run water/alky injection to cool the intake and control detonation. You will be able to run 92 octane with quite a bit of timing on the flat tops. You can use a nitrous plate to spray the water/alky mix. (windshield washer fluid for cold weather works like a charm).
    Aquamist makes a good kit.
    OR- build it as a 377 and keep the big dome pistons. Your compression would come down slightly but your RPM range would go up. Remember, it's the low-mid RPMs under heavy load that breeds detonation. A 377 with a dual tunnel with a couple of 500's will scream with lots of cam and 1.6 rockers.

  10. #10
    I would stay away from Hyperutetic pistons in a marine application. For the price of a set of Speedpro/TRW forged flattops it's cheap insurance. Go with a forged flattop piston and a set of aluminum heads so you can safely run on 93. There's no sense running an iron head with high compression in the marine enviroment. AFR, Dart, Brodix all make nice aluminum 195-215cc heads that would suit you application. I prefer AFR and run their 190cc's on my 355. I would at least want a 195cc or better yet the AFR 210cc head on a 406ci. I really like the Crane 230/238 .528/.5?? 112LSA hyd roller for 383 and 406ci SBC's. Comp also has a nice 230/236 112LSA hyd roller. How high do you plan on spinning the engine? I don't see a Vic Jr being needed if you don't spin above 6000 rpms. The RPM Air Gap is stronger in the low and midrange and holds it's own over the Vic Jr until around 6K. A Jet needs torque bottom line. A Holley 750 or 800DP will work nicely.
    If you don't want to pop the coin for aluiminum heads and plan to use the stockers definately pop for some new flat top pistons. The 58cc and 12.5-1 domes will not work. Getting 500hp from a 400ci is pretty easy but will ultimately come down to how well the heads flow. The better the heads flow the easier it will be to reach your goal.
    Are you planning on using the stock 400 crank?

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