502 Chevy Jet boat engine....
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502 Chevy Jet boat engine....

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    Resident Ford Nut Sleeper CP's Avatar
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    Default 502 Chevy Jet boat engine....

    Although I'm a Ford guy I have designed a couple of Chevy's for a friend or two. This one we were looking for a 650 HP engine +/-. We got it real close:


    Sleeper CP
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    Foxwell Motorsports
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    Quote Originally Posted by Sleeper CP View Post
    Although I'm a Ford guy I have designed a couple of Chevy's for a friend or two. This one we were looking for a 650 HP engine +/-. We got it real close:


    Sleeper CP
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    LOL...I just loked at the date on the sheet.
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    Quote Originally Posted by steelcomp View Post
    LOL...I just loked at the date on the sheet.
    Well better late than never

    I wanted 10:1 or 10.25:1 it would have picked up 25-30 hp but the owner didn't want to change the pistons in the factory 502 short blk. He purchased the short blk and then it was blueprinted and we had the heads built for it and Crower did a mild roller cam for it.
    He then put a 150 hp shot on it.

    Sleeper CP

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    Senior Member Baja Big Dog's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    Well better late than never

    I wanted 10:1 or 10.25:1 it would have picked up 25-30 hp but the owner didn't want to change the pistons in the factory 502 short blk. He purchased the short blk and then it was blueprinted and we had the heads built for it and Crower did a mild roller cam for it.
    He then put a 150 hp shot on it.

    Sleeper CP
    Hard to believe that was 12 years ago...is it still running??

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    mo balls than $cents$ IMPATIENT 1's Avatar
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    got a build sheet on it, he won't mind if its been so long i'd like to know the cam specs

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    Quote Originally Posted by Baja Big Dog View Post
    Hard to believe that was 12 years ago...is it still running??
    Best of my knowledge yes. It is now in a sterndrive and I don't think it has ever been a part except to replace the rollers. I'll check on that.

    Quote Originally Posted by IMPATIENT 1 View Post
    got a build sheet on it, he won't mind if its been so long i'd like to know the cam specs
    Not the entire build sheet but I'll did up the cam spec's. I think I can find them somewhere. I'll add them to an edit to the first post when I find them.

    I think it is interesting the Air Flow numbers, it kind of show's you how many jet boat's are over carb'd.

    Sleeper CP
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    Quote Originally Posted by Sleeper CP View Post
    Best of my knowledge yes. It is now in a sterndrive and I don't think it has ever been a part except to replace the rollers. I'll check on that.



    Not the entire build sheet but I'll did up the cam spec's. I think I can find them somewhere. I'll add them to an edit to the first post when I find them.

    I think it is interesting the Air Flow numbers, it kind of show's you how many jet boat's are over carb'd.

    Sleeper CP
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    And over cammed.... Good power, though.
    Last edited by steelcomp; 12-24-2007 at 08:03 PM.
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    Quote Originally Posted by Baja Big Dog View Post
    Hard to believe that was 12 years ago...is it still running??
    I know they say it won't last but I know of 2 Jets with GM crate motors.

    One is a stock 502 short block with a cam change, some worked iron heads and a 177 blower pushing about 6psi max.

    The other is a 454 crate longblock with a cam change.

    The 502 has been going for about 10 years. the 454 has been in for about 7. and both are still running.

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    Quote Originally Posted by IMPATIENT 1 View Post
    got a build sheet on it, he won't mind if its been so long i'd like to know the cam specs
    The cam spec's on the roller were:
    Dur. @ .050 260-268 lift of .650 .655 on a 114* lobe sep.

    Keep in mind a dump in compression to 10.5:1 would have probably added 25-35 HP. I guess mid range at about 30 would be a good estimate. That would have put this mid 502 at 680 HP.

    Sleeper CP

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    Fiat48,

    Try to apply these number's to your program. I'll look for the observed numbers but I'm not sure if I can find them:

    Sleeper CP
    Last edited by Sleeper CP; 12-27-2007 at 07:12 PM.

    "Dark Sarcasm"
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    Senior Member H20MOFO's Avatar
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    Forgive my ignorance, wouldn't a rect port head make more power on top? Or did you feel it wasn't worth the trade off.
    Another Hot Boat refugee

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    Quote Originally Posted by H20MOFO View Post
    Forgive my ignorance, wouldn't a rect port head make more power on top? Or did you feel it wasn't worth the trade off.
    AS you guessed there was a trade off. The owner of the engine wanted to make a lot of torque but didn't want to bump the compression to help out so we traded off top end performance to make sure the mid-range was more than enough. That's why we used the oval port heads.

    We were shooting for 600 lbs. trq but fell a little short of it. However if it was my engine we would have run it again with the oil temp at 195-200 degree's and it would have made more than 600 ft. lbs. You can see from the dyno chart it was run at 160 degree's oil temp. That is about 40 degree's to low if you ask me.

    Sleeper CP
    Last edited by Sleeper CP; 12-28-2007 at 09:29 AM.

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    Senior Member Baja Big Dog's Avatar
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    Quote Originally Posted by Sleeper CP View Post
    AS you guessed there was a trade off. The owner of the engine wanted to make a lot of torque but didn't want to bump the compression to help out so we traded off top end performance to make sure the mid-range was more than enough. That's why we used the oval port heads.

    We were shooting for 600 lbs. trq but fell a little short of it. However if it was my engine we would have run it again with the oil temp at 195-200 degree's and it would have made more than 600 ft. lbs. You can see from the dyno chart it was run at 160 degree's oil temp. That is about 40 degree's to low if you ask me.

    Sleeper CP
    How did they keep the oil that cool?? Was the thermocouple accurate..I agree..that seems low..

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