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compression
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  1. Jet Boats
    How much compression will AV gas support ?
  2. Bob Teague
    Hey guys/gals I have a 588 NA motor (Dart Big M tall deck, 4.56 bore) with AFR 335 heads that is at 700hp on the dyno, compression is 10.5 to 1. I would like to see the motor more around 800-850hp, so I figured best bet would be to put a Whipple 3.3 on her, but compression is obviously to high...
  3. GN7 On the Dyno
    This is not a strictly boat-related question, but you guys know motors. I need to rebuild the motor for my 65 El Camino project- it had a 327 in it, all forged parts, but the stupid body guy left it in the rain and it will need new pistons or a new block- it was .030 over and will need to go to...
  4. GN7 On the Dyno
    Some of you may like the powerband and this is good example of OEM Type GM heads and the "ISH" I talk about.... Customer called this winter with Land Speed Class project. She is a 4 speed camaro. With gearing he needed peak power at around 7400. 565 Combo 14 to 1 BMF385 Customer was on...
  5. Bob Teague
    I am looking at buying a new E85 496 stroker jet boat motor for my 20.5 ft open bow carrara and have the option to choose compression. Ive read all kinds of different numbers so i thought i would ask you guys what you think. Ive seen anything from 11.1-16.1 i would like to see what you guys...
  6. V-Drives
    Curious what compression ratio (and cam specs) you guys are getting away with on pump gas? I am in the process of building a 468 chevy for my Hondo and trying to decide what kind of compression I want to end up with. I want to be on the edge of pump gas, don't mind blending, but do not want to...
  7. V-Drives
    Hey fellas looking for a educated opinion .Ive drag raced and hot rodded cars for years .I also know things are a Little different with the boats .my question is what kind of compression ratio is good for a high performance N/A lake boat. I'm currnetly planning on running a MoPar super stock...
  8. GN7 On the Dyno
    What is a safe CR for a pump gas 496. I have been told from 10.5:1. Then another said it would rattle at the CR. What is safe for 91 pump gas? About to order pistons and want to stay safe. This is for a lake boat with a little NOS. Thanks for your help.
  9. Parts for Sale
    bbc sbc hi compression mini starter this stater was used maybe 15 start ups then put back in the box 165 shipped fits bbc sbc
  10. GN7 On the Dyno
    I'll keep it short and sweet, from what i've always been told the higher the octane the slower the burn. Once you up the compression depending on how high, you are going to go into running V.P. I'm at 9.5:1 am I losing power running 91 as opposed to 89 or does it even matter. 454 BBC with a mild...
  11. GN7 On the Dyno
    i was thinking of bumping up my compression from @ 8.5:1 to 9:1 to get better off the line results. will i loose power on the top end beings as i will have less volume to pack with boost? boost will be run at @12,20,&@25psi+. might wanna run e85 or alcohol temporarilly for playtime. at what...
  12. GN7 On the Dyno
    Looking for some info on e-85. Im trying to figure out what to do with my motor set-up for next yr. Current motor is a 565 that i picked up as parts to put something together. I have been told that it has lived on c-19 or c-20 ( i forget) all its life. Motor has a Static compression ratio of...
  13. GN7 On the Dyno
    Ok, trying to figure out compression ratio on a proposed build, maybe need an education on the subject. Have a couple assumptions I need help with. Inch to cm conversion is inch x 2.54? Volume of a cylinder is: stroke x 3.14159 x 1/2 bore squared, right? Of course must add in head gasket cc...
  14. GN7 On the Dyno
    Looking at the 509 Twin turbo build and trying to settle on a piston...dish or flat top. I imagine whatever set of heads I go to will be a 118-124 cc chamber. So, I am trying to see what thickness I would do for a cometic gasket to get me right around 8.5 on the compression. I want to stick with...
  15. Outboards
    Question- I have a "new to me" Mercury outboard (2.5 lt carb unit) with factory re-manufactured powerhead- mercury sticker on block shows 7/20/12 re-man date- suppose to have 97 hours since replaced. The compression is high but un-even- I have run the motor twice on a stand- results did not...
  16. GN7 On the Dyno
    How much H P gain should you get in a 2.5 points in compression say like going from 10.5 to 13 to 1 rough estimate Thanks,
  17. GN7 On the Dyno
    I bought a 13:1 468 gen IV big block Chevy that was built ten years ago and put in storage. The block has o-rings and the new dart heads are machined around the combustion chamber as well. My goal is to get more compression. The motor has SCE copper gaskets P/N 013524 which is a 4.520 bore...
  18. Parts for Sale
    Not for sale No longer available for sale Please delete. Thank you
  19. Jet Boats
    I just bought a bitchin 77 Daytona, and its got 13.5:1 compression!! The guy I bought it from recommended I use 25% Race Fuel, the rest 91octane.. Any thoughts on this? Anyone ever use some of the Octane booster stuff? I called "Race Gas Concentrate" ( Race Gas | Racing Fuel Concentrate ) and...
  20. GN7 On the Dyno
    Found a set of brand new arias large dome pistons sitting on a shelf. 4.280 bore but compression height is 1.56. Only config I see these working in is a tall deck 4in stroke with 6.635 rod! Any one have any ideas before they become ash trays?
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