The Stovebolt Site Forums The Shop Area Engine Shop 235 valve/lifter question

I have a problem on my 235 that I need some opinions on. My engine has hydraulic lifters and if I pre load them the engine will miss on #5 cylinder at idle. I have narrowed it down to the exhaust valve. If I run that lifter loose to the point it ticks, the miss will not be there and it runs perfect. I have run a compression test and have 130 psi on all cylinders. I have pulled the lifters, dis assembled,cleaned, reassembled and soaked in oil. I set the preload with the engine running by loosening the valves until they tick then tighten until quiet. Thoughts on this?

The plunger is sticking in the bore, and won't accept a preload. Remove that lifter and give the piston a mirror polish on a felt buffing wheel with jeweler's rouge. Do the same thing to the bore of the outer part with a gun cleaning wool mop and rouge, chucked into a drill motor. The plunger should slide freely in and out of the lifter when the lifter cleaned of all oil with a solvent such as brake cleaner, without sticking.

BTW, your adjustment procedure is incorrect, according to the service manual. It's virtually impossible to get the correct preload on a lifter with the engine running.
Jerry

Jerry thanks for the advice. i will pull that lifter and polish like you said. I tried setting the preload like the manual I found said and all the valves were held open giving zero compression to start the engine. There are so many ways to preload on the old interweb it is a bit overwhelming. With these being aftermarket lifters, from a previous engine builder i have no clue what the proper preload is.

When you “pre-load” the lifter cold, some of the lifters may not be pumped up and will feel the plunger spring before you get any real resistance. I spin the push rod until it takes out any play and I feel a slight resistance, then turn it down the specified amount. I prefer 3/4’s of a turn but others have their preferences.

Edit: You need to just feel the plunger spring without compressing it, and that will be your zero lash starting point. Thanks Pre ‘68 Dave for pointing out my unclear instruction.

A week valve spring can cause the same problem.
The extra pressure from the spring you compress in the lifter when it is set, can over power the valve spring, holding the valve open.

Kinda have the same problem hope someone can help
I’m new to the forum I have a 69 c10 with the 250 4.1 L6 we just rebuilt it and upon first start we found number 2 cylinder had a miss and virtually no compression. Took the head off found a crack. I purchased a rebuilt head from tom at 12Bolt.com upon first start we found the identical problem a miss in number 2 and virtually no compression (my guy says he got 30lbs) is this a coincidence or is there something I missed…I need help ….please any suggestions are welcomed
Pacman

Turned out to be a bad seat on #5 exhaust valve. Head has been rebuilt.

Pacman Learned that if that version of 6 gets hot it can crack between the lifter bores along with the head,saw it on a 292 combine engine in about 1971.