Cam reccos for 1970 z28 w/ m21 and 4:10s

Discussion in 'High Performance Modifications' started by Rosster, Jan 12, 2021 at 9:50 PM.

  1. Rosster

    Rosster Veteran Member Gold Member

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    As some of you know I'm deep in the throws of rebuilding the original engine and the car will be returned to stock condition except for hooker headers and flowmasters. I’ve gone back with stock components (forged 11:1 pistons, 186 heads w/ SS racing valves and howards springs/retainers, forged rotating assy, etc. I purchased a howard’s copy of the original cam (going to keep with my spare parts) but am thinking I’m wanting something with a little more aggressive idle. I used the GM 140 cam in my last build and it was too radical for my tastes. Any thoughts on which howards flat tappet cam might be a good pick to gain a little power and sound a little hotter?

    my intended use is as a casual driver for local cars shows and short cruises.
     
  2. 70lt1z28

    70lt1z28 Veteran Member Gold Member

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    You will be getting many comments about going to a roller cam setup, and with good reason due to the risk of flatting a lobe since you are willing to go away from a 100% restoration cam. If you want to stay with a flat tappet, you may want to consider the 1969 Z28 "30-30" cam GM PN 3849346. It has a bit more intake lift and duration and a 114 degree lobe separation. This will also bleed off a bit more cylinder pressure and allow you to run pump 93 octane without pulling the timing back too much.
    Cam comparisons:
    https://www.summitracing.com/parts/crn-967251/overview/make/chevrolet
    https://www.summitracing.com/parts/crn-110951/overview
     
    Last edited: Jan 13, 2021 at 9:15 AM
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  3. Rosster

    Rosster Veteran Member Gold Member

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    funny, I was actually looking at that one! Looks like a good choice with a little more radical idle
     
  4. Lowend

    Lowend Administrator. .a car, a man, a maraca. Staff Member Lifetime Gold Member

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    If you want a period correct cam that's a small step up from the Factory Z28 model I recommend the Isky Z-50
    It has a little more duration than the factory LT-1 cam (less than the 140), but with much more aggressive ramps and a 108 Lobe Separation. The idle isn't for the faint of heart, but I've seen it used in similar engines on streetcars many times before.

    I'll spare you the "don't use flat-tappets" speech for today
     
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