93flatbed

We all know how to adjust the valves to factory tolerances of 0.010" and 0.020".
But I've read about going tighter. And we all know tighter is better in most cases. I've read that some guys have gone as much as 0.005" and 0.015". The information I'm looking for is what is too close. I hear that it will hurt top end but help spool big turbos. And I'm going to try to swing a big single, but my transmission has killed my bank account so a cam is out of the question right now.
Thoughts?

crewcabxlt

i set mine .090 and .018 . you can get away with tighter but i worry more about burnining a valve than hitting i piston.

texsasdiesel

i always go .008 and .018 on mine. seems to quiet them down just a bit, i agree about worrying more about burning a valve up than hitting a piston, but i don't think that being on the tight side will hurt anything in this case.

James

92smokin blacky

Mines at .009 and .019. Not sure if it made much difference cuz I installed studs and put in 60 lb springs at the same time. It sounds a bit different but I found a few of my stock springs didn't seem to have much resistance anymore

93flatbed

The hitting of a piston was not my worries. More like stress of the valve train at higher rpm's. But mainly my question was the stories I've read, about tighter valves helping to spool bigger turbos? With my little experience and basic know how I understand how it will in effect allow more air in and out of the cylinder but don't know if its going to allow the tappets to skip off if the Camshaft. Or am I way off base here?

maybe368

I know 1 thing that is true of any type of engine, with valves, a little loose is better than a little tight...Mark

93flatbed

Back to the top, any one agree or disagree?

maybe368

What I mean is that if your are going to err, it is better to err on the loose side, it is best to set them to specs, IMO. I found this generalization on the crane site...Mark

The engine only responds to the actual movement of the valves. Since the valve cannot move until all the running clearance (valve lash) has
been taken up, the amount of valve lash you use affects the engine’s performance. For example, if you decrease the amount of (hot) valve lash,
the valve will open slightly sooner, lift higher, and close later. This makes the camshaft look bigger to the engine, because of a slight increase of
actual running duration and lift. If you increase the amount of (hot) lash the opposite occurs. The valve will open later, lift less, and close sooner.
This shows the engine a smaller cam with slightly less actual running duration and lift. You can use this method on a trial basis to see what the
engine responds to and keep the setting that works the best. Just remember, the more lash you run, the noisier the valve train will be. If the
clearance is excessive it can be harsh on the other valve train components. Therefore, for prolonged running of the engine we do not
recommend increasing the amount of hot lash by more than +.004" from the recommended setting. Nor do we recommend decreasing the hot
lash by more than -.008".
Warning: “Tight Lash” camshafts cannot deviate from the recommended hot lash setting by more than +.002" increase, or -.004" decrease.
“Tight Lash” cams are those which have recommended valve settings of only .010", .012", or .014" on the specification card. These lobe
designs have very short clearance ramps and cannot tolerate any increase in the recommended valve lash. The extra clearance can cause
severe damage to valve train components. With “Tight Lash” cams, we recommend using only the prescribed amount of hot valve lash, and that
close inspection of the engine be maintained.

93flatbed

So crane would tell me I could run them 0.016" & 0.006" and still be in the safe range.
Now mark I understand what you are trying to say to me on the error on the caution side, but hey if I break something it would give me an excuse to the wife for pulling the engine apart........again and starting over........again. honestly that would be the best, if its broke she can't say no, just no to the "but honey it will make it go faster". Man I hear NO alot!

maybe368

I think that they are saying -.008, or .008" less than specs. I think the point is that they are saying how much it affects timing. In the old days, with hydraulic lifters, you used to count turns on cold setup, then, when it was running, you loosened them until they clattered,then tightened until the noise stopped. With hydraulics the point is to get the plunger in the middle of it's travel range within the lifter. I have an idea so as to not have to break anything, loosen the adjustment until it makes a horrible racket, tell her it blew something and needs rebuilt. That way no needlessly broken parts...Mark

j_martin

Valve lash is set at the point that minimum impact damage (hammering) will occur and the valve won't be held open when it's supposed to be firmly closed, including hot, cold, fast, slow, etc. It's an engineering specification found by a combination of calculations and experience.

The effect of any valve lash adjustment within the above parameters on valve timing is miniscule.

The reason exhaust valve clearance is always more than intake valves is that the exhaust valve changes temp over a wider range, and more clearance is needed to ensure it doesn't get too tight when the valve is hot.

I think I'll stick with the factory settings.

Unrelated, but mentioned in the thread.
Hydraulic lifters use a light spring to maintain zero lash, and a piston in a cylinder with a very small or none existent exit port and a one way valve to allow oil in. During operation the piston is compressed very slightly, maybe .001", so when the valve closes, it closes completely, and the above mentioned light spring then takes up the lash, drawing a miniscule amount of oil into the lifter. When you get things moving fast enough so the valve train parts try to fly apart, the hydraulic lifters will try to take up the lash and hold the valves open. That's the dreaded valve float.

When you adjust hydraulic lifters, you adjust to zero lash, then add a turn. If you do it when the engine is running, it will miss for a few rounds till the lifter compresses back to zero lash. That's an old timer's trick to checking the lifters. If it doesn't miss, the lifter is worn out. If it misses and doesn't stop, the lifter is sticking. With a bit of experience, the proper setting can be felt and heard easily.

maybe368

I guess I should say that crane is talking about their hi-performance cams, and I would think that they know something about their cams. I think that running tighter is running "closer to the bone". Less lubrication, more heat, etc.. Any return would be erased by these things. I have never heard of anybody running tighter valves in performance settings, but I have heard of running more clearance...Mark

j_martin

It makes sense engineering wise that if you are running a cam with extremely quick lifts (square cam we used to call them) that you'd want lash to be a little tighter to limit impact damage. Like I said in my above post, the setting is a compromise based on engineering and experience. Go with the cam manufacturer.

Rick 12v CTD

I just went with cummins OE recommendations but I think I'm going to give hamilton cams a call and see what they recommend for me... Some useful info in this thread.

Bencie

I was always told a little tighter helps top end and a little loose helps torque.