Topic: ? on setting valve lash

[Roger S]

But what are the pushrods doing in relation to the crank and piston? that's the other 1/2 of the situation. Make sure you're turning the engine in the right direction. The intake pushrod moves outward/opening valve, then goes inward. After it stops moving inward, continue moving the crank till the piston comes to the top. That's top dead center of the compression stroke and where we're saying move the piston downward a 1/4" from here and set valves.

If you turn the crank another full turn till the piston is at the top, the exhaust valve will just be closing and the intake just opening at the same time. You can't set the valves here, at the end of the exhaust stroke and beginning of the intake stroke as the valves are not both fully seated. The cam turns 1/2 the speed of the crank; the cam lobes will only be in the same relation to the piston on every other revolution of the crank.

[hiflyer727]

I am turning the crank in a clockwise direction. At TDC both valves would be closed, I then go past that to set the valve lash. However, as I continue turning the crankshaft thru the strokes and come to the intake stroke the valve will open  1/2 to 3/4 of the way then that is all the further I can turn the crankshaft, unless I want to bend another pushrod. I can not figure out what is the problem!

[Roger S]

Have you done anything to the heads.. is there enough valve travel, guide, springs, retainers related.

[hiflyer727]

I had George do all the head work. I believe he shaved .075" off of them. He also replaced the stock springs with he heavy duty ones, etc.

[George Herrin]

The only thing that could be happening is the retainers might be bottoming out. Check that to see if its happening. I have yet to see this be an issue. Without b eing there to see specifically whats going on this is stuff trying to diagnose. If I were there it would be an easy issue to resolve I am sure.

[Roger S]

At this point we have to ask what might seem like dumb questions, as we aren't there to see it. Have you backed the rocker adjustments off as far as they'll go, or not touched them since it ran stock. That would cause a valve to run out of travel or hit a piston since the heads were cut, maybe thin gaskets added, and cam has increased lift.

[George Herrin]

good point

[hiflyer727]

Well, believe me, any question you ask is not a dumb one, it would be very easy for me to overlook something obvious here. Now to answer your questions: The stock rockers were replaced with roller rockers from EC. So I did set the valve lash at .004" when I installed them. Looking in the spark plug hole I can see that the valve is not hitting the piston. The head gaskets used are just stock Briggs gaskets, and the cam I have came from this engine, sent it to Precision, and returned. All I know about it is that Precision says it's a "373 Special Grind" cam. I do not know how much the profile has changed from stock.

I suppose I am coming down to two options here soon; one would be to spend 10 hours driving down to you, George, and have you take a look at things. I know with gasoline prices being what they are that would be a costly trip, especially if the problem is a simple fix.

[George Herrin]

373 CAM IS a common grind put several in. Try this just for giggles. add a lock washer for a 1/4" bolt under the roller rockers I bet that will solve the issue, if so let me know I will send you longer pedestals (square mounts) for your rockers. I have run into a situation where with all the mods and new cam the end result is the rockers had to be raised a tad meaning that with all the mods the push rods wound up being a bit too tall... So add the 1/4 inch lock washer under the pedestal and retighten and tell me if this fixes your issue.

[hiflyer727]

You had sent me the taller pedestals, and the problem still exists. Do you want me using a lock washer under these also?

[George Herrin]

NO if it has the taller pedestals then thats not it look at the retainers and see if they are bottoming out...

[hiflyer727]

That does not seem to be an issue. The intake valve will open about 3/4 of the way then stop. If I back out the adjustment screw maybe 4 or 5 turns then the valve will completely open. As I continue turning the crank the valve will close, however; now the push rod just wobbles because the adjustment screw is backed out too far.

[George Herrin]

It just sounds like either the retainers are bottoming out or the valve is binding. Wish I could see it.

[hiflyer727]

Well, George, upon further checking, I believe you are right; the retainers are bottoming out. What can be done to correct this? Thanks.

[nor66]

grind the valve guide down.