502 engine build up what you guys think
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502 engine build up what you guys think

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    Default 502 engine build up what you guys think

    ok im new to this BBC stuff and high perforance for the boats

    i have a 89 20.5 Advantage classic bow rider jet boat with a Dom. pump


    we picked up a short block that is a 502 gen 4 bow tie punch out to a 4.560 bore they say its now a 522.6 ci

    H beam rods not sure whats pistons the paper work says 10.6

    heads a Canted/Oval Pocket Ported large Valves
    in. v 2.190 ex v. 1.88
    combustion space of 111.51cc
    comp cam gross .575 both in and ex
    @50 dur. 253
    110 lobe center

    stealth intake
    850 deman carb


    but the lifter bore is bad so now its all apart just was wondering what you guys thought of this package good or bad since the motor is now apart i can rethink this if i have too

    we have had 1 trip out in it and about 6 hours and it did seem to run pretty good

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    what are the actual head casting numbers?
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
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    Quote Originally Posted by SmokinLowriderSS View Post
    what are the actual head casting numbers?
    not sure what they are the machine shop has them clay smith put them on the old boat motor in 99

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    I actually think it'll be a good strong motor.

    The Demon may be a problem. Some folks like them, some folks have a lot of trouble with them (mixture distribution issues). Have you got room for a 4-hole spacer under the demon?

    550to 575HP perhaps and a good strong torque curve.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
    H.L. Mencken

    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

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    Quote Originally Posted by SmokinLowriderSS View Post
    I actually think it'll be a good strong motor.

    The Demon may be a problem. Some folks like them, some folks have a lot of trouble with them (mixture distribution issues). Have you got room for a 4-hole spacer under the demon?

    550to 575HP perhaps and a good strong torque curve.
    what will the 4 spacer plate do??

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    Senior Member DuaneHTP's Avatar
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    Everything looks pretty good except the cam. A jet boat motor of that size needs at least a .650" lift.

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    Quote Originally Posted by DuaneHTP View Post
    Everything looks pretty good except the cam. A jet boat motor of that size needs at least a .650" lift.
    so i should go roller then?? to get that much lift

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    Senior Member Bigblockbill's Avatar
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    Quote Originally Posted by slugbug View Post
    so i should go roller then?? to get that much lift
    Sleeve the lifter bore and put a roller in it!! I agree you could definatly use more lift (.650-.750)

    I am not a fan of the demon carbs either. Buy the Holley HP 900 or 1000 and life will be good.
    24' Eliminator Fundeck

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    AARP Member Rocket-J's Avatar
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    Question 502 BBC block.

    Quote Originally Posted by slugbug View Post
    ok im new to this BBC stuff and high perforance for the boats

    i have a 89 20.5 Advantage classic bow rider jet boat with a Dom. pump


    we picked up a short block that is a 502 gen 4 bow tie punch out to a 4.560 bore they say its now a 522.6 ci

    H beam rods not sure whats pistons the paper work says 10.6

    heads a Canted/Oval Pocket Ported large Valves
    in. v 2.190 ex v. 1.88
    combustion space of 111.51cc
    comp cam gross .575 both in and ex
    @50 dur. 253
    110 lobe center

    stealth intake
    850 deman carb


    but the lifter bore is bad so now its all apart just was wondering what you guys thought of this package good or bad since the motor is now apart i can rethink this if i have too

    we have had 1 trip out in it and about 6 hours and it did seem to run pretty good
    A real 502 (part #10237292) is a Gen VI block. The maximum bore recomended by GMPP for that block is 4.500". You might want to sonic test the block to check the cylinders too make sure it is worth putting more money into. The 502 has been a good foundation for a Big Block project. Also make sure you get the correct head gaskets for that block. Al

  12. #10
    jetboataholic HawaiianJet's Avatar
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    Quote Originally Posted by SmokinLowriderSS View Post
    I actually think it'll be a good strong motor.

    The Demon may be a problem. Some folks like them, some folks have a lot of trouble with them (mixture distribution issues). Have you got room for a 4-hole spacer under the demon?

    550to 575HP perhaps and a good strong torque curve.
    What does the 4-hole spacer do under the demon? I just bought a Demon 850.

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    E-7 Sheepdog (ret) SmokinLowriderSS's Avatar
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    Quote Originally Posted by HawaiianJet View Post
    What does the 4-hole spacer do under the demon? I just bought a Demon 850.
    DuaneHTP above has a lot of experience with them, dynoing motors with 8 O2 sensors, and finding a lot of mixture dist. troubles from cyl to cyl. Some running very rich, others dangerously lean, all coming out evenly if you only check at the collectors.

    From what I recall of his postings, it seems to even the mixtures out some, not a cure, but a band-aid.

    He's really the one to ask.
    "As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron."
    H.L. Mencken

    OBAMA: Some people deserve this.
    The rest of us are being dragged along kicking and screaming.

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    If it has a couple of messed up lifters then just bush those holes and no worry about doing the rest unless the shop is paying for it.

    At 522 CID you need a single plane intake. Once you get over 500 CID don't worry about lossing low end torque. The CID pulls so hard on the intake that a single plane will be more effective all over especially with your situation with oval ports and the CID you have.

    Cam wise for the long term a roller is going to be more cost effective just cost more up front. Flat tappet stuff these days have a short life. With cores in question, lifters in question, and the EPA getting rid of anti wear additives in oil a flat tappets day is numbered. Also you can look at it this way, if during break in the cam goes flat and you have to replace it and the lifters and then tear the engine down to clean it . . .well your dam near at the cost of a roller set up.
    Chris Straub
    Straub Technologies

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    Senior Member cyclone's Avatar
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    Quote Originally Posted by Rocket-J View Post
    A real 502 (part #10237292) is a Gen VI block. The maximum bore recomended by GMPP for that block is 4.500". You might want to sonic test the block to check the cylinders too make sure it is worth putting more money into. The 502 has been a good foundation for a Big Block project. Also make sure you get the correct head gaskets for that block. Al
    i'm pretty sure the max you can bore that block is 4.530....i'd check it like RocketJ suggested.

  16. #14
    Senior Member Bigblockbill's Avatar
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    Quote Originally Posted by slugbug View Post

    we picked up a short block that is a 502 gen 4 bow tie punch out to a 4.560 bore they say its now a 522.6 ci
    Quote Originally Posted by cyclone View Post
    i'm pretty sure the max you can bore that block is 4.530....i'd check it like RocketJ suggested.
    Guys, he does not have the Gen VI block as per first post. My Bow Tie Gen IV went 4.560 with no problems as well.
    24' Eliminator Fundeck

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