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  1. #1
    Join Date
    Jul 2016
    Location
    Manchester
    Age
    48
    Posts
    52

    advice on sbc 350 engine rebuild

    hi,
    I am looking for advice on rebuilding my chevy 350 engine which I stripped today.
    its all standard inside ie shells camshaft and pistons.
    the timing chain looks stretched and the camshaft looks worn.
    I would like to change the camshaft to a performance one, without compromising on tickover and day to day use.
    and I'm not sure whether to stick to flat tappets or go to a roller follower set.
    which is best??
    Last edited by Des Mc; 11-02-17 at 10:49 PM.

  2. #2
    Join Date
    Nov 2006
    Location
    Shropshire/Wales Border
    Age
    48
    Posts
    5,942
    No reason you can't put a mild performance cam it in and it wont hurt the idle noticeably. Couple of things to check.

    1. Any performance cam will usually increase valve lift over standard. That's what you want, but you must check the valves can actually open that far! Either manually open the valves and put a dial test indicator on them or check on line for the specs if you know what the heads are. Remember the lift generated by the cam is multiplied by the ratio of the rocker arms. Standard arms on an SBC I think from memory is 1.5 (check that), but performance rockers will increase that ratio and therefore lift. So .4" lift at the cam becomes 0.6" at the valve etc.

    2. Flat tappet v roller. There are pros and cons to both.

    Pro's first.
    Flat tappet cams are cheaper
    The followers are lighter and help when aiming for higher RPMs. Not that critical in a mild performance build.
    If you have flat tappet now, then you may get away with using the same pushrods by staying with a flat tappet cam. Roller lifters are generally longer, and often will require you to buy shorter pushrods.

    Roller cams allow a more aggressive cam profile, so even if the max lift is the same, the valve will open quicker = better performance.

    The critical difference is that flat tappet cams MUST be very carefully broken in otherwise its very easy to wipe a lobe. Use a high zinc content break in oil, and get the engine instantly up to 2,000rpm when you start it and run it for a good 10 minutes at that speed. Don't let it idle or rev the nuts off it. Once broken in, switch out the oil. A roller cam by its nature means you will have non of these issues.

    If you want a more performance and peace of mind then roller cam is the way to go but will cost a fair bit more and you may need new pushrods. If you want to manage the budget/have a simple install then use flat tappets and hopefully existing rods but do be careful breaking it in. As you aren't aiming for ultimate performance then I'd go for the hydraulic version of either lifter, saves you constantly adjusting the tappets. In all probability if you have a stock SBC its running flat tappet hydraulic lifters now.

    HTH
    Lloyd B
    Current: Crendon #54 in build - 427 Side Oiler/Cobrajet Heads/Dual 600cfm Holleys/4 speed toploader/Vintage cast knock on wheels
    Dedion Dax/Clarkson 383 Chevy with roller 4/7 swap cam, AFR195 heads - SOLD

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