308s valve clearance

Discussion in 'Race 400/430/455' started by BQUICK, Oct 5, 2020.

  1. BQUICK

    BQUICK Well-Known Member

    What clearance do you like to run (cold)?
    Cam card say much more clearance like .024/.028 but I run .014/.016.
    If I run what what is on card it gets real loud when hot....
     
  2. Bens99gtp

    Bens99gtp Well-Known Member

    Are you running iron heads or aluminum... the aluminum grows much more when warm which will give you extra clearances there.

    I have aluminum heads and on my solid cam I run .012/.015. I still need to take the time to check the warm measurements so I know what to set too after its started if I ever have an issue at the track.

    I run my a little tighter to gain a touch more duration.....my cam isn't a 308s but still solid setup
     
  3. BQUICK

    BQUICK Well-Known Member

    Yeah aluminum Ben....

    Idled better with loose clearance but embarrassingly noisy. Unsure why TA shows such loose numbers....
     
  4. Bens99gtp

    Bens99gtp Well-Known Member

    well it wi idke better/ smoother......effectively with looser setting you are reducing duration and lift slightky as the valve doesn't move till the slack is taken up and things are shorten by the same amount in the other side.....its minor but it is there

    I think my old 308 card had similar number and listed as warm then crossed out and had some other numbers writen as cold
     
  5. Tom Righter

    Tom Righter Well-Known Member

    BQUICK I’ve always set them .005 tighter with aluminum heads.
     
  6. Thumper (aka greatscat)

    Thumper (aka greatscat) Well-Known Member

    Me too
     
  7. BQUICK

    BQUICK Well-Known Member

    Still that would be .019/.023. Tried that and quite noisy hot. Like I said, I ended up with .014/.016 cold.
    Would having 1.65 rockers play into it?
     
  8. Tom Righter

    Tom Righter Well-Known Member

    .014/.016 Cold would be fine. I don’t believe the rocker ratio would play into it. Although I would say the geometry isn’t ideal with the factory Shaft set up.I know with my old race motor and having the jesel set up the valve train was quieter.
     
  9. Thumper (aka greatscat)

    Thumper (aka greatscat) Well-Known Member

    I have the 308 in our cars and I set them about the same as you.
     
  10. BQUICK

    BQUICK Well-Known Member

    Seems odd that TA specified such loose clearances.....and people are going alot tighter.
     
  11. Tom Righter

    Tom Righter Well-Known Member

    BQUICK, Are your adjusters pretty close to being flush with the bottom of the rockers?
     
  12. BQUICK

    BQUICK Well-Known Member

  13. Stevem

    Stevem Well-Known Member

    Yes running a high lift rocker does play into it if your looking for the most added peak hp!

    Setting on high lift rockers with there faster opening rate hitting the Intake valve makes the engine think that the Cam has been advanced and to correct for that the Cam needs to be retarded 1.5 degrees and .002"to .003" lash needs to be added to the Intake valve setting.

    With most motors if you have not done the build norm of advancing the Cam 2 degrees to compensate for normal timing chain run stretch then you can leave the motor as is and just add lash, of course this all assumes that the motor was run on the dyno in the first place before high lift rockers where installed to determine where the best installed point of the Cam in question was calling for.
     
  14. BQUICK

    BQUICK Well-Known Member

    Never knew a higher lift rocker would change things that much. I just put cam in at 4 deg adv and walked away......
     
  15. Bens99gtp

    Bens99gtp Well-Known Member

    Yes about the only thing that doesn't physically change on cam numbers when you change rocker arm ratios is seat to duration.....and lobe separation angle......I think every other measurement is effected
     

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