valve to piston clearance with high lift camshafts

Discussion in 'Small Block Tech' started by Buickboy69, May 13, 2018.

  1. Buickboy69

    Buickboy69 Active Member

    Ok guys so was wondering how big of a cam can you run before you need notched pistons just some food for thought.
     
  2. Mart

    Mart '71 350 GS, almost stock

    I run .584 lift. Don't think I can get away without notches.
     
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  3. Buickboy69

    Buickboy69 Active Member

    I was looking at running the ta 413-350 cam which is 0.500 lift intake and exhaust with 10:1 shallow dish pistons my heads have been milled 0.030 as well so was really wondering if i would have any clearance issues.
     
  4. hugger

    hugger Well-Known Member

    Best way to tell is put some play doh in there and see, I feel better visually seeing the clearance vs using checking springs. But with the tiny 350 valves I'm guessing it will clear. Don't forget get you move cam timing to increase distance

    Duration gets people in trouble more than lift alot of times
     
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  5. Buickboy69

    Buickboy69 Active Member

    thanks hugger yea definitely will be breaking out the play-doh to double check i have the ability to retard or advance the cam 4 degrees with my timing gear really didn't know where the point of no return was as far as cam size and piston sizing the duration on that cam is 234 int. and 244 ext. at 0.050 and advertised is 286 int. and 296 ext.
     
  6. Jim Blackwood

    Jim Blackwood Well-Known Member

    Don't know why the 350 should be much different from the 340. With the aluminum 300 heads on my 340 block, zero decked pistons with a shallow dish, .050" head gasket and .436" valve lift the clay showed about 1/4" of valve/piston clearance. Pretty sure that makes it a non-interference engine.

    You can bring the piston to TDC, remove the intake valve spring, and measure how far the valve drops before contacting the piston.

    Jim
     
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  7. Buickboy69

    Buickboy69 Active Member

    thanks Jim i wouldn't think that it would hit the top of the piston but I guess I wont know until I check it I was just fishing for info more than any thing before I start ordering parts my oil pump went out and killed a couple of cam bearings so i figured I'd upgrade while i had the motor out.
     
  8. Mark Demko

    Mark Demko Well-Known Member

    That's exactly what I do, I didn't know if anyone else did it this way:D
    I figure that's the closest the piston will ever get to the valve, if the valve doesn't hit the piston in that scenario, it never will.
     
  9. Stevem

    Stevem Well-Known Member

    Many times it's not the max valve lift where the tightest clearance happens, its at around the 200 duration point!
     
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  10. 87GN_70GS

    87GN_70GS Well-Known Member

    Maximum lift has nothing to do with v/p interference. It's duration. At max valve lift, the piston is some 2+" down in the bore. At TDC, during overlap, is where interference occurs, and the valves are only open a little.
     

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