Cam trouble? Valves not staying adjusted

mmkid · Jun 13, 2023

I have a 6 cylinder I am trying to get going. Engine will
run for 10 or so seconds and then quit. Acts like
something is binding in front , by cam/water pump.
Occasional smoke/steam out front breather. After that bit
of running , valves will be way out of adjustment.
Stumped. Cam is on gear fine, key in place. Any
suggestions on what may be causing this? Thank you

rustred · Jun 14, 2023

need more info on what you mean by valves getting out of adjustment. if the valves are set they dont just change like that. plus on what tractor? plus it sounds like you have had it apart already.

molinegb · Jun 14, 2023

mmkid · Jun 14, 2023

605 b

mmkid · Jun 14, 2023

Its a 605b power unit in a GTBD. I adjust the valves and then after it quits , after it ran for a tiny bit and then quit they have 3/8 inch play between rocker and valve on a couple of them. After adjusting them, a half hour before and having it run hardly at all.

MMDEL · Jun 15, 2023

If it has 3/8 inch of play, check your push rods to see if they are bent.
MMDEL

J.Wondergem · Jun 15, 2023

Are the valves sticking open?

SWMolines · Jun 15, 2023

Are the threads stripped out in the rocker arms or on the adjuster?

mmkid · Jun 15, 2023

Thanks for the replies. The push rods arent bent , the
valves arent sticking open , and there isnt stripped
threads on any of the adjusters or rocker assemblies. I
am just as stumped. Going to take off timing cover again
and see if maybe the cam gear is sliding in or out too far?
Any suggestions? Thank you

rustred · Jun 15, 2023

i would say explain your valve adjustment procedure, cause they do not just go out of adjustment. you explain that then i have better info to go by.

T.R.K. · Jun 15, 2023

Has it done this more than once?

If it was me working on it and that happened once, I would suppose the cam was not on TDC before the power stroke -like I thought it was- but at TDC before the intake stroke. At that point, both valves can be partially open at that point, So adjusting them there will give some pretty wild valve clearance later on. (I usually get it right the second time.)

ChrisQ · Jun 15, 2023

Has it done it more than once and only on the same couple valves? If a lifter is worn crooked from not rotating it could maybe do something similar. Have you had cam and lifters out of the engine?

wore out · Jun 16, 2023

Have you drained the oil and checked for metallic debris in it and the oil sump? If something is that far amiss in the valve train there should be evidence of parts being chewed up.

Indiana Ken · Jun 16, 2023

If I understand correctly, it is the same couple of valves that get out of adjustment? To adjust these valves and remove the excess clearance, (3/8) are you always turning the adjustment screw the same direction to remove the clearance? I think the answer to this question has to be no.....? How much adjustment do you actually make on the adjustment screw?
Perhaps the push rod is missing the ball on the end and some how getting hung up on the edge of the lifter. When you adjust the valves it is hung up on the edge; when the engine runs it slips off the edge resulting in the clearance.....? You might remove the the push rod/lifter from the problem cylinders and compare them to the push rod/lifter from the good cylinders; look for any differences between the components.

rustred · Jun 17, 2023

u need to work with us,... everyone is asking questions and ur not replying. you cant get to the bottom of this by not helping us out. we have no idea on your mechanical knowledge nor do we have eyes on it.

VicS · Jun 22, 2023

I'll go with a bent pushrod

mmkid · Jun 22, 2023

Its a 605b power unit in a GTBD. I adjust the valves and then after it quits , after it ran for a tiny bit and then quit they have 3/8 inch play between rocker and valve on a couple of them. After adjusting them, a half hour before and having it run hardly at all.

J.Wondergem · Jun 22, 2023

How do you adjust the valves, when the piston is on top as is fires?

mmkid · Jul 2, 2023

There is nothing showing in oil. I have 10 times brought number 1 to tdc and adjusted those 2 and its running mate pistons 2 valves. Then on to the rest. Same thing. I have rebuilt many mm engines. Have adjusted valves same on every other one. The ball is not missing, I have taken push rods out , all straight. Nothing appears to be funny in any way with rockers. Getting oil.

J.Wondergem · Jul 3, 2023

Explain how your getting to top dead center. You must be over looking something. We're trying to help you find it without being there.

This post was edited by J.Wondergem on 07/03/2023 at 07:39 am.

Cam trouble? Valves not staying adjusted

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