BBC Cam
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BBC Cam

  1. #1
    Senior Member APOLLO's Avatar
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    Default BBC Cam

    Can someone tell me what the benefit is for a 4-7 swap on a cam is for and what the benefit is. For what ever reason, I see a lot of them.

    Thank you

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    Senior Member ap67et10's Avatar
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    from what i hear there isn't all that much to gain power wise. its just easier on the crankshaft. i don't remember all the details, but i'm sure there are people here that know more than i do about these.

    i do know that gm made the switch on the new LS engine, so that has to say something right there.

    AP

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    The will help to prevent crank harmonics in large stroke engines. HP gains are minimal in most cases.
    Chris Straub
    Straub Technologies

    3HP is an A$$ Whooping!!! JW

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    I've never heard of this 4-7 cam? Can someone tell me what it is?

  7. #5
    Senior Member Factory1's Avatar
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    The actual cam core has the 4 and 7 lobe positions changed up which changes the firing order. The result is a smoother running engine. Nothing you will notice with your ear, but your engine will. I've also heard of changing up one other set of cylinders as well, but can't remember what #'s.

  8. #6
    steelcomp was here
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    Quote Originally Posted by Factory1 View Post
    The actual cam core has the 4 and 7 lobe positions changed up which changes the firing order. The result is a smoother running engine. Nothing you will notice with your ear, but your engine will. I've also heard of changing up one other set of cylinders as well, but can't remember what #'s.
    The Pro Stock guys tend to swap another pair, and it's the LS1 firing oder. Those cores are hard to come by and expensive.
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  9. #7
    Senior Member Jim W's Avatar
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    Quote Originally Posted by steelcomp View Post
    The Pro Stock guys tend to swap another pair, and it's the LS1 firing oder. Those cores are hard to come by and expensive.
    Steel,

    is there a actual "core" with a billet cam????

    Jim
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  10. #8
    steelcomp was here
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    Quote Originally Posted by Jim W View Post
    Steel,

    is there a actual "core" with a billet cam????

    Jim
    Material wise and heat treat depth, yes. A "core" for a lobe that never gets ground smaller than .550 isn't going to be the same as a core with a lobe that might get ground to .450 or smaller. Materials also vary, depending on whether or not the cam is on rollers or flat bearings. 55mm roller cams are rare and take a special core, then add to that the LS1 firing order. I'm pretty sure the lobes are roughed in, then the "core" is shelved, awaiting a final lobe grind, so even though you may have billet cams, they're with different firing orders, materials, heat treat, etc. Heat treat is done before the final grind.
    There have been issues with the 55mm cam cores and the LS1 firing order being ground to smaller lobe profiles than they were designed for by a certain company. They were being ground through the hardness.
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    New here Beer:30's Avatar
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    Quote Originally Posted by PowerAddict View Post
    I've never heard of this 4-7 cam? Can someone tell me what it is?
    Wow.

    As mentioned, cyls 4 and 7 are swapped along the cam lineup, so the spark plug wires get moved also.

    The firing order changes to 18736542 from 18436572.
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