Max compression for BBC pump gas
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Max compression for BBC pump gas

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    Default Max compression for BBC pump gas

    Give me some recommendation for rebuilding 588 BBC from Flat tops currently to max comp you have had success without detonation, going in an I/O twin. Aluminum heads on motor.

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    Quote Originally Posted by Jspeeddemon View Post
    Give me some recommendation for rebuilding 588 BBC from Flat tops currently to max comp you have had success without detonation, going in an I/O twin. Aluminum heads on motor.
    We've got a similar sized motor we set at 10:1 and not having any problems with the swill that passes for 91 octane unleaded premium in CA. Heard of guys running a bit higher, but tune up gets trickier....
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    Way to open ended question that will spark alittle conversation here.
    But it has ALOT to do with the expected RPM operating range, camshaft and the exhaust system and the size of the boat, for starters.

    You can get to around 10 to 1 with the flat tops by making sure the deck is close to zero. maybe remove a little from the heads. After that its a custom piston with a small dome. Not sure its worth that. IMO

    Like David said, you need to be on your tune above that, and the boat better be pretty light.
    Last edited by gn7; 01-02-2012 at 12:12 PM.
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    I would say the size of the boat and consistency of your "pump gas" would be the main concerns. What you give up in power on a bit of compression might be worthwhile for safety margin.

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    Like the Bob said. Alot of things can make a differencs. I run as high as 10.5 on 91 octane. Run timing as high as 36 depending on the componets used.
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    Quote Originally Posted by EVILFORCE View Post
    Like the Bob said. Alot of things can make a differencs. I run as high as 10.5 on 91 octane. Run timing as high as 36 depending on the componets used.
    I run 10.6 on my 572 with aluminum heads,lighting headers,solid roller cam,big oil coolier,with a rich tune told by a a/f guage in a 5000 pound 28' Nordic Heat on 92. 36 max on timing, I like 32 to be a little on the safe side. It spins 5700 rpms.

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    Quote Originally Posted by I DIG IT View Post
    I run 10.6 on my 572 with aluminum heads,lighting headers,solid roller cam,big oil coolier,with a rich tune told by a a/f guage in a 5000 pound 28' Nordic Heat on 92. 36 max on timing, I like 32 to be a little on the safe side. It spins 5700 rpms.
    Curious. What did you use for pistons to get to 10.6. Are they custom?
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    GN, I did 10.6 on a 555 with head gasket thickness thinner made 10.8


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    Certainly not trying to be controversial, just want a little feedback on what others have experienced with compresison and pump gas.
    How about the scenario of mixing in E85 in a consistent basis for detonation preventitive or may consider some CAM 2 at say 5 gallons for every 15 gallons of premium. Interested in pushing the power level up, from curent flattop setup, have even considered running all E-85 with electronic fuel injection. A little feedback from ohters , always helps to head off problems. Thx.

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    Quote Originally Posted by Widetrack View Post
    GN, I did 10.6 on a 555 with head gasket thickness thinner made 10.8
    not saying you can't get there. Just curious how. Not with a flat top and a 118 chamber. Off the shelf 1,25/10.5 pistons for a 555 are alot easier to come by than for a 572/588
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    Quote Originally Posted by gn7 View Post
    Curious. What did you use for pistons to get to 10.6. Are they custom?
    Yes the pistons were made by Venolia and they are not flat tops they have a slight dome to them
    I have a 4.625 bore
    and a 4.25 stroke
    so I think it more like a 571.??? ci we all call them 572's
    then engine blueprint specification sheet says 10.59 compression ratio

    I do not know half as much about motors as alot of people on the board, but I do keep a close eye on mine I have alot of guages to tell me what is going on all the time. I know that Im running close to the safty margin. But I belive that the motor will live for many years. I change the oil every 10 to 15 hrs and do not run the chit out of it all the time. And ALWAYS run fresh 92 fuel. At the end year I suck all the old out and put fresh fuel in the spring. I never let the fuel sit for more than 2 weeks
    Last edited by I DIG IT; 01-02-2012 at 05:56 PM.

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    Quote Originally Posted by Jspeeddemon View Post
    Certainly not trying to be controversial, just want a little feedback on what others have experienced with compresison and pump gas.
    How about the scenario of mixing in E85 in a consistent basis for detonation preventitive or may consider some CAM 2 at say 5 gallons for every 15 gallons of premium. Interested in pushing the power level up, from curent flattop setup, have even considered running all E-85 with electronic fuel injection. A little feedback from ohters , always helps to head off problems. Thx.
    How much power are you wanting and at what rpm?
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    I would like to get to 800 N/A, I have AFR 357 CNC'd heads, solid roller, adding EFI to engines with this rebuild, which I already own 2 FAST units. I know you are slick on Cam tech and profiles CStraub, I currently use a Howards 260/270 @050 .675 .675 lift cam. Stellings headers. What compresion do you feel will get me to 800 @ 5700-6000?

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    Are all of these numbers static compression or dynamic?

    Matt.

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