Blower on 2 bolt main block?????
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Blower on 2 bolt main block?????

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    Senior Member jockorace's Avatar
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    Default Blower on 2 bolt main block?????

    Ok guys, simple question.......what are the chances of keeping a 2-bolt BBC together if it were limited to 6,500 (1/4 mile at a time only....really) and boost limited to 7-8 psi. Timing max. 34 degrees total. This dealio would be run on 110 Sunoco or E-85/98. My thoughts were that DETONATION would be the biggest enemy. The rotating assembly would be fully internally balanced. Fire away! Jocko

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    Ain't Right Racin piston in the wind's Avatar
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    Quote Originally Posted by jockorace View Post
    Ok guys, simple question.......what are the chances of keeping a 2-bolt BBC together if it were limited to 6,500 (1/4 mile at a time only....really) and boost limited to 7-8 psi. Timing max. 34 degrees total. This dealio would be run on 110 Sunoco or E-85/98. My thoughts were that DETONATION would be the biggest enemy. The rotating assembly would be fully internally balanced. Fire away! Jocko
    Stud the bottom end have it honed. Shouldn't be a problem. I've ran12# with av gas years ago with out studs.

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    Default Whats to lose???

    I think you might consider what the rest of the build cost initially.... Just how much will you lose if it fails? The cost of a "better" block, IMO, would be cheap insurance to prevent catastrophic failure... Not to mention the safety factor of blowing up in the lights.... I often wonder why GM went to the 4 bolt blocks if the 2 bolts were just as good?? Trucks??

    Ray
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    Dave mine is a 2 bolt studded alky job ,its a retired drag motor I just try to keep it under 7 Gs its going on year 7
    Last edited by mdsheppie; 01-21-2013 at 05:19 PM.

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    Senior Member jimclauss's Avatar
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    Quote Originally Posted by jockorace View Post
    Ok guys, simple question.......what are the chances of keeping a 2-bolt BBC together if it were limited to 6,500 (1/4 mile at a time only....really) and boost limited to 7-8 psi. Timing max. 34 degrees total. This dealio would be run on 110 Sunoco or E-85/98. My thoughts were that DETONATION would be the biggest enemy. The rotating assembly would be fully internally balanced. Fire away! Jocko
    Go for it, pull the timing back to 30 max.

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    Senior Member jockorace's Avatar
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    Quote Originally Posted by Moneypit View Post
    I think you might consider what the rest of the build cost initially.... Just how much will you lose if it fails? The cost of a "better" block, IMO, would be cheap insurance to prevent catastrophic failure... Not to mention the safety factor of blowing up in the lights.... I often wonder why GM went to the 4 bolt blocks if the 2 bolts were just as good?? Trucks??

    Ray

    Thanks for the input Ray, and I agree with you completely. However, this is not a build I'm doing. If it were a build like I've done many times, it would start as a 4 bolt or I would add splayed 4 bolt caps. I am considering a short block that is priced very well, has a forged 4.25 stroker crank, studded 2 bolt main caps, Isky roller cam, flat top forged pistons, etc. With the $$$ I save by buying this SB, I can buy some decent heads now. The only reservation I had was that it 2 bolt. Hmmmmmm. Jocko

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    Senior Member jockorace's Avatar
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    Quote Originally Posted by jimclauss View Post
    Go for it, pull the timing back to 30 max.


    That's probably good advice, since I don't want to rattle it at all. Jocko

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    gn7
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    The 2 bolt caps themselves are no weaker than the 4 bolt caps. The additional bolts only aid in controlling cap walk. Keep it at or below 6500, and stud it and it should be fine.

    Depending on the compression, you can run that timing easy with 110 or E85. With 98 I bet you end up closer to 36.



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    Senior Member jimclauss's Avatar
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    Quote Originally Posted by gn7 View Post
    The 2 bolt caps themselves are no weaker than the 4 bolt caps. The additional bolts only aid in controlling cap walk. Keep it at or below 6500, and stud it and it should be fine.

    Depending on the compression, you can run that timing easy with 110 or E85. With 98 I bet you end up closer to 36.
    with that fuel no problem I thought he was running pump gas, I only run 28 to 30 on my blower engine. on alky
    Last edited by jimclauss; 01-21-2013 at 08:17 PM.

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    gn7
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    Quote Originally Posted by jimclauss View Post
    with that fuel no problem I thought he was running pump gas, I only run 28 to 30 on my blower engine. on alky
    Depends alot on the compression as well. Its never about just the boost.
    Alky can be a little more forgiving about the timing. Get it too retarded with gasoline, and it will burn itself into the ground.
    I am running more than 8 lbs of boost, and a shitload more compression the he is guaranteed, and I can ruin a set of headers in one race if I back it off to 28.



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    Quote Originally Posted by gn7 View Post
    Depends alot on the compression as well. Its never about just the boost.
    Alky can be a little more forgiving about the timing. Get it too retarded with gasoline, and it will burn itself into the ground.
    I am running more than 8 lbs of boost, and a shitload more compression the he is guaranteed, and I can ruin a set of headers in one race if I back it off to 28.
    I run around 28 lb boost, timing can be real funny thing. My one alky pro stock engine ( big chief head ) picked up 100 hp by pulling timing out of the engine. doesn't like anything more than 30 degrees figuire that one out.
    Last edited by jimclauss; 01-22-2013 at 05:06 PM.

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    Quote Originally Posted by jimclauss View Post
    I run around 28 lb boost, timing can be real funny thing. My one alky pro stock engine ( big chief head ) picked up 100 hp by pulling timing out of the engine. doesn't like anything more than 30 degrees figuire that one out.
    there is a huge difference between the combustion chamber in a Big Chief and a conventional BBC head. Big Chiefs don't need the timing and its counter productive if it gets to far out there.
    Stock Ford 429/460s don't need the timing the BBC needs either. The 118 cc chamber on the BBC heads suck!



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    Built a 454 2-bolt for a guy. Had a 177 merc blower on it . Kinda a Merc copy. 7.9 to 1. He put a 420 mega blower on it with a chiller. Still running and he beats on it in a 24' Hallet. The 990 heads liked 33 deg. on 91 rocket. I think he dynoed it at like 899 or 901 hp after swaping some AFR's. I wouldnt do it but its still together. Probably 6-7 years and about 130-150 hours. I would have never thought.

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    Senior Member jockorace's Avatar
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    Thanks again to all of you for the input. That being said, I've gone ahead a bought this shortblock and will probably get it running on race gas and then later install my E-85 carb conversion kits. Gonna start conservative on the timing & start at 5% over on the blower. If I gear it with 25's or 29's it should easily be at or under 7,000 thru the lights with a 16 pitch prop. First thing I'll do when I get this thing in a week or so is pull it apart to double key the crank for the blower hub, plus check all of the bearings. Next step will be finding some decent aluminum heads. Jocko

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