Technical Chevy 250 valve adjustment problem HELP!?

I was adjusting valves on my chevy 250 while running. Engine started missing and stalled half way through adjustment. Now it misfires and will not run without idle way up, and still wants to stall and backfire. I may have adjusted the rocker nuts too fast. What can do I do to check for damage?

 

Sounds like you bottomed out some lifters. Back them off until they are loose and go through the adjustment procedure over again. You should be fine.

 

I have to go with what he said in post 2. Back them off and start over.
I'd have to think that you cranked them down too far after they quit clicking. I usually go 1/2 a turn after they stop clicking.

 

Yes


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Hydraulics are normally maintenance free, as time goes on.
Why the need to readjust hydraulic lifters to begin with ?
Were you having a problem that led you to the lifters ?
Adjusting lifters is a slow, methodical process, not like torqueing wheel lug nuts down, as fast as you can, as a comparison.

 

Eric, how many turns did you put on the nut after the click went away ? I ask because even though that engine should have a hydraulic cam and lifters I've run into surprises that suggested differently.

 

Was the engine at operating temperature??
Oil has to be HOT, to allow for the lifter to bleed off while adjusting..
As you say you may have turned the adjusting nut too fast and "hydrauliced" them, back off and try again slowly..
Or, maybe the internal piston/valve has jammed up on the carbon / gunge buildup inside the lifter..
If this is the case, back off a couple of turns till the offending valve rattles, they should free themselves with a fast idle, then, take them down 1 at a time till the rattle just stops, then SLOWLY down 1/2 to 3/4 of a turn..

 

I don't recall having tried to adjust valves with the engine running, since I was a pup.

 

I had noise from the rockers, and a mechanic friend reccomended that I check the valve lash. When I was adjusting the rockers, I went 3/4 turn past zero lash.
When I run the engine it is missing badly (I can hear the miss out the exhaust pipes) and it will backfire out the carb and then stall. It started doing this just after tightening the rocker on cylinder three, or maybe four, I am not exactly sure.
My brother built engines and he reccomended the EOIC (exhaust open, tighten the intake, then intake closed, tighten the exhaust rocker, do them by firing order) method to set them cold. I would like to try them cold, since it is difficult to keep the engine running, and with the missing it is loud enough to make it hard to hear the rockers clack.

 

I found this on another message board. Does this sound like a reasonable way to set the rockers?
Assuming it's a stock engine, put the #1 cylinder in firing position, then set both valves on #1, intake on #2, exhaust on #3, intake on #4, and exhaust on #5. Turn it over one full turn so #6 is in firing position. Set both valves on #6, intake on #5, exhaust on #4, intake on #3, and exhaust on #2.

 

THat's one way to do it....I just start with #1, adjust both of the #1 rockers, turn the crank 1/3 turn, the do #5 rockers, then another 1/3 turn, do #3, etc all through the firing order.

One thing is that it kind of takes a "feel" to know when there is just zero play. Some folks do this by twisting the pushrod, but that doesn't work for me...I prefer instead to "rattle" the rocker arm--back off the nut so the rocker can clack up and down a bit, then slowly tighten until it just can't move. Then move to the next one. I set them all to zero, then when I'm done with that I just go and tighten all of them the 1/2 turn (or full turn, or whatever) preload.

It's worked for me for decades, doing it this way.

 

Thank you. I'm going to give it a try today. Hope it works!

 

Also, try to find a couple more "mechanic friends" so you'll have several opinions.

 

the 250 has hydraulic lifters, doesn't it? If you needed to adjust at all I think you would want to know which lifter might have been giving you trouble and give that one attention. Not all of them. Also, I do believe hydraulics are adjusted while running and no tighter than what it takes to quite it.

 

Just to further talk about this. I had a person ask me to check his 283 after doing exactly what OP had done and is experiencing. His problem wasn't as bad as Erik's because he stopped at zero lash on a solid lifter cam. I find it odd that OP's lifters have not bleed down on there own from just sitting ? We'll just have to wait and see.

 

Yes, agree to not over tightening and to adjusting the hydraulic lifters, only while running.

 

I'm betting you have all the adjustments set WAY too tight.
The adjusting sequence shown above is the way to go ..... for mechanical lifters.
For HYDRAULIC LIFTERS ONLY, before starting the engine, I would back off each rocker, one full turn, then start the car, let it clack away, run engine until its at normal operating temperature.
Then begin the adjustments.
WORKING WITH ONE ROCKER ARM ONLY, rotate the rocker nut SLOWLY, until clacking noise goes away, on that specific rocker.
Then SLOWLY ...... tighten that specific rocker 1/2 turn to 3/4 turn. You're finished with that rocker.
Onto the next rocker arm. SAME PROCEDURE, as written just above.
On hydraulics, all rockers are adjusted easily, while engine is hot and running.
If a rocker does not quiet down, after an adjustment, you may have a defective lifter, a bad cam lobe or a filthy engine, with plugged oil passages.

 

Thank you, every one. I adjusted the rockers with the engine cold and not running, by the method given by squirrel.
I found the #4 exhaust rocker was almost a full turn too tight!
I also found that two of the spark plugs were slightly loose. This is what was originally causing the ticking noise that I suspected was a loose rocker arm.
It ran great after the adjustment, with the spark plugs now tight, and the rocker arm 1/2 turn past zero lash.
Thank you again

 

thanks for the report! Yeah, fixing cars is fun...don't worry, you'll keep learning new things, every time you work on one. I do.

 

That's exactly how my Cousin used to do it. He just passed away last week but he was a damn good Mechanic and Troubleshooter. And anytime we needed the valves adjusted, we would call him up and he never failed to show up and do the job. God Bless him!

 

Sorry for your loss.

 

Thank you.

 

Learning is always a good experience, when you enjoy what you're doing !