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Thread: BBC what stroke to use?

  1. #1
    Member JOURNEYMAN
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    BBC what stroke to use?

    i have always used stock length rods and crank but sevral years ago i bought a rotating assembly with a gm steel 454 crank that had the rods machined to 2.100 and was offset ground. it has bill miller aluminum rods and 4.560 venolia pistons. i have a bowtie IV block 4.560 bore. i want to replace the rotating assembly with new and i can't decide which stroke to go with. 4.25 or 4.50 or ?? i just don't have that much knowlege on which set up has more or less trouble with the added stroke. i would appreciate any imput. thanks matt

  2. #2
    Senior Member RACING JUNKIE
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    Re: BBC what stroke to use?

    Quote Originally Posted by shortyems3307
    i have always used stock length rods and crank but sevral years ago i bought a rotating assembly with a gm steel 454 crank that had the rods machined to 2.100 and was offset ground. it has bill miller aluminum rods and 4.560 venolia pistons. i have a bowtie IV block 4.560 bore. i want to replace the rotating assembly with new and i can't decide which stroke to go with. 4.25 or 4.50 or ?? i just don't have that much knowlege on which set up has more or less trouble with the added stroke. i would appreciate any imput. thanks matt
    No doubt I'd go 4.375 stroke, almost every 4.5 combo I've seen doesnt run that great for what it is.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines
    www.apdracing.com

  3. #3
    Senior Member EXPERT BUILDER
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    what are goals?what deck do you have a tall or short?how much torque you want?budget?you kinda gotta tell some specifics of your combo?boat drag street what?ive got a 572 10:1 compression with roller cam and love the torque....the bigger the better as long as the bigger torque will hook up if its a drag application.just remember the more you wander from the 1/4" increments of the stroke the harder itll be to find off the shelf pistons!i wished 4.625 stroke combo in a tall deck combo was more readily available.

  4. #4
    Member JOURNEYMAN
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    i 've got an 81 camaro tube chassie 2300 - 2400 lbs. 4 link dana 60 410 gear power glide w/brake. injected methanol dart 360 heads. bowtie IV 10.2 deck, i still need a few components like cam, belt drive or gear drive.... i like to be able to run in the mid 8.'s and would like to get the best price on good parts. i'm not totaly against used parts. 4.375 .. have you had any problems with this combination? i heard that the longer the stroke, like over 4.5, the more stress there is on the pistons and cylinders along with clearance problems.. and do you think there will be that much differance in hp.

  5. #5
    Senior Member EXPERT BUILDER
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    seeing as it a tall deck i vote go 4.5" for the fact that you can run a 6.7 rod and get still a decent rod to stroke ratio.off the shelf pistons will be another benefit.with a 4.6" bore and 4.5" stroke your getting right up to 598 cubes!!!plus those are big heads so either go big cubes or wind up tighter a smaller cube motor.what are your rpm limits?compresssion?cam selection?im in the same boat i got tube chassis chevelle with a 572 (pump gas 10:1) and wanna run low 9's and spray deep in the 8's.with an over cammed mph of 143 on a 90 degree day first time at track ill be there no prob when i regrind cam to correct duration....if you build big cubes,you wont have to wind up real high!valve train HATES RPM!!!!

  6. #6
    Member JOURNEYMAN
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    i've never had a motor with over 500 inches, mostly 482 and 440 so the cam selection will take some more research. since i plan to run injected methanol, like i have in the past i think the compression ratio should proably stay around 13.0 to 14.0. with the 4.10 gear i think the rpm should be around 6800 to 7000 but i also have a set of 488 if i need to increase that. i've noticed alot of engines that are using the 4/7 swap cams, i'm going to check them out. i've used isky, crane and lunati in the past. ihave a comp cans solid flat tappet cam in my steet camaro... i haven't had bad luck with any of them.

  7. #7
    Senior Member MASTER BUILDER
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    combo

    My 572 has the 4.50 crank, 6.800 rods, and 1.12 piston height.

  8. #8
    Member JOURNEYMAN
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    the 4.5 crank with 6.535 rods and either 4.560 or 4.600 sounds like a good combination....6.800 thats a pretty long rod , how high do you crank it?

  9. #9
    Senior Member RACING JUNKIE
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    I am still voting for the 582 tall deck or not. Get a cam from Reher Morrsion they have a good selection of Erson cams.
    David Lanning
    IHRA NHRA 387B

    Fleenor Racing Transmission
    419-280-1406
    Lanning Electric
    Complete Drag Car Wiring
    APD Race Engines
    www.apdracing.com

  10. #10
    Member JOURNEYMAN
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    i like that combo too ! is that what you run in your car? i'll check out reher & morrison and see what they think on a cam.


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