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How sensitive is the valve adjustment?

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sparkydave

sparkydave

Jedi Knight
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I checked on the valve lash this evening, partly because it sounded like I had at least a couple of loose ones, and because it had been a couple thousand since I last checked. The book says 0.010", but most were more like 0.013", and two were at 0.016". I got them tightened up, but without changing anything else, suddenly the engine seems to be running more evenly, and the slow idle was now up around 1500 RPM when it was 800 before. I'm not griping about the smooth running though, it would be bucking occasionally at speed, and once I backed the idle back down, it just sounds better overall. Now I wouldn't have guessed that a few thousands of an inch would have changed valve timing that drastically, but did it? I know you don't want them too tight or they won't seal when hot.
 
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Now I wouldn't have guessed that a few thousands of an inch would have changed valve timing that drastically, but did it? I know you don't want them too tight or they won't seal when hot.

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Iguess it could make that much difference. Especially at idle. Idle would be the condition that is most sensitive to small changes in valve timing.
D
 
Sparky:

Resetting the valves to stock spec is fine, but if you're not sure, it's always safer to be a little loose (even if it is "tickey"). Less chance of burning a valve.
I run my 1500 at 0.016" for racing. Taps a bit, but valves hold up nice.
 
Ditto that. Actually, I recall that Kent recommends (for their TH5, at least) that you set valve lash to .022 to .024. This is more than double stock valve lash. I set mine around 15-16 thousandths, like Nial.
 
Hmm... Now I'm puzzled. Is 0.010" not a good spec to go by? Do I need to go make sure I can still get a skinny feeler gauge inserted while they are hot? Sorry for all the questions, I'm just puzzled by the big change in idle speed and wanting to make sure I don't burn valves.
 
0.010" is the correct number and if you are sure the feeler gauge fits, then that's fine.

If you are not sure if the 0.010" has enough "drag", make it just a pinch looser, just to be safe.

If I were doing it, I'd make it so the 0.010" would slide easily but a 0.013" would have a noticable "drag".
 
Thanks, Nial. I think I may have them too tight then; the 0.010 fits snugly, and the 0.012 is almost a no-fit.
 
Oh boy! It looks like I get to do my valves again. Ughhh!
 
If they seem worn use a wire gauge to set the gap. You will eliminate the "low spot" factor of the equation.
 
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If I were doing it, I'd make it so the 0.010" would slide easily but a 0.013" would have a noticable "drag".

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Nial, you are an absolute genius! I tried this technique last night, and my car runs smoother and better than EVER!!!!

Don't tell the other guys, but you are my favorite.
 
:p !!!! /ubbthreads/images/graemlins/lol.gif
 
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