I always ask here first because I trust your opinion, skills & experience.
My car started popping through the carb, right after I put on a new set of Edelbrock heads. My first thought was a valve spring broke. I took off the valve covers and discovered the rocker on #2 exhaust was loose. The rocker arm nut did not back out. I tightened it 1/4 to 3/8. So my thoughts were then I lost a lobe on my cam. However the more I think about it, the more I think I lost a lifter. Once I snugged the rock to the point that the pushrod wouldn't spin by hand I could actually push it in by pressing on the rock arm. I don't ever recall being able to push a lifter in and out with hand pressure. I slowly snugged the rocker arm until the valve started moving up and down again.( while running) It will now run without popping. I call it my mechanical hydraulic lifter. If it starts popping again I know the lobe has worn down more.

Do you think the lifter has collapsed or the cam is bad? I don't know if it's wishful thinking but I think I may only have to replace the lifter.

 

I would measure the movement of the rocker at the valve tip or the end of the pushrod and compare it to a known good one to see of you have a bad lobe.
Use this:
https://www.harborfreight.com/1-in-travel-machinists-dial-indicator-63521.html
or this if you don't have a base or some way to hold it.



A lifter can be compressed if it doesn't have oil in it. So your lifter may have just not been pumped full of oil when you noted you could compress it.

 

Thanks that is really what I needed to know. I guess I just never tried on a lifter that wasn't pumped up before.
​​​​​​​

 

The valve springs that your running are they matched to the camshaft.
Post the process that you used to adjust your valves. The pushrod should still be able to spin between your fingers at the point of zero lash.
Zero lash is the point that pushrod and rocker arm are just touching a slight resistance should be felt.

 

I slowly tightened the rocker arm to the lash point ( it clicked loudly and the the pushrod just stopped being able to spin by using my fingers) then I slowly turned 3/4 more.
A week later the engine started popping through the carb. So I removed the valve covers and found #2 exhaust valve loose and no longer moving up and down keeping the valve closed. So I played with it. I found the lash point and turned it 1/4. Keep in mind the rocker tip is lower than the others now. I basically tuned it by ear as this was the smooths spot the engine will run. I know I need to fix it. I even asked for some help picking a cam. Its just that I have been thinking about this so much I now recalled having a collapsed lifter 2o years ago and only had to change the lifter and not cam & lifters.

 

Zero lash is not when the pushrod stops turning. Zero lash is when the pushrod will not move up and down LOOSELY anymore. Below is an alternate way to explain how to do it.

You can use a .003" feeler gauge between the valve stem and the tip of the rocker and tighten the rocker nut until you can tell the feeler is is just starting to drag in there, then go a half turn tighter.

 

To find the lash point I have always relied on it still being loose rather than at the point that the push rod stops turning. However if the engine is running I would back it off until it made the clacking noise. I would find that fine line of it clacking and not and use that to move forward. I see the difference though Spinning and moving up and down are very different but in my case this seamed to be almost at the same point. I appreciate your explanation for me.
It kind of reminded me that years ago we had a difference of opinion in my family on how much to turn the rocker arm nut after finding zero lash. Dad insisted 1 full turn. One of my uncles said 3/4 of a turn. I actually emailed Crane once they gave me the specs. Both seamed to be within the tolerances and correct
.
In this case there was an obvious difference a week later when I reinspected to find the cause of the popping.
I could tell the lobe was wiped or the lifter collapsed.
With the first reply I received I'm thinking the issue lies with the cam because I did try to readjust the valves while running and clearly lost the height that the others have.
Since the engine was running the lifter should of pumped up, Of course maybe there is mechanical failure of the lifter. So that's is what as me going back and fourth, is it the lifter or cam? Ugh!!

 

nevermind

 

Hey 1860army i saw your reply. I appreciate what you wrote. A friend of mine is worried that metal maybe getting into the bearings too. I never heard of that paint trick but I will do it. If I understand correctly after I put a painted witness mark on the pushrod it should be spun after I run the engine. Should I be able to see it spin while running? If so that is a good sign meaning the cam's lobe is still good. How long do I need to run the engine for this test? I would love for it to be a lifter.
I was concerned by making the lifer act like a solid lifter I could hurt the cam. I appreciate that your replay addressed that too.

 

Dave,
Glad you saw it and hope it helped.... I re-read it after I posted and it sounded like I was preaching or something and I was late for an all you can eat Oyster Dinner (OMG was it good)- so I deleted it.

I know you want it to be a collapsed lifter and I do too, for you.... But you have to make sure and cranking the adjustment down like you mentioned is not going to do your engine any good. I don't know what your experience level is but make sure you fully understand the proper or accepted way to set the lash on these valve trains so you are sure your are doing it right. Once you do it the right way if there is still an issue you can try the good old, loosen it till it clacks, ease it down until it stops clacking and give it half a turn more. I've done it both ways, depends on the circumstances. You are using high zinc oil, right?

So at this point I would spin off the oil filter and remove the media, stand it up on a thick wad of paper towels which will help drain the oil out, takes a couple days but once most of the oil is out you can clearly see how much metal is in the media. There is usually a fleck here and there but it should not be loaded with it. Cam/lifter metal is like mud and the flecks are small, I use a magnified bench light to look.

If the filter checks out OK then readjust the suspect valve the correct way, #2 exhaust rocker arm nut will probably be lower than the others, not a good sign but does not tell you what's wrong. I pull the plugs and spin the engine with a large ratchet on the harmonic balancer nut. Then I would measure the cam lobe lift as mentioned above and also check the valve in the other cylinders of that bank to see how they compare(see Pic below). Remember intake and exhaust have different lift values so make sure you are checking the exhaust valves...If #2 is significantly less than the others then its time to get the wrenches out, most likely the cam. If #2 is the same as the others but you have to crank the rocker nut down further to set lash then you have a shot at it being a lifter issue. Either way you have to fix it, just cranking it down until it stops making noise will lead to more trouble.

If you choose to check the pushrod spin, mark a number of them so you can see the difference, they don't spin fast. The cam lobes of a flat tappet cam are cut at a slight angle that imparts a spin to the lifter riding on it, promotes even wear. When it gets wiped that angle is gone and the lifter does not spin. Start the engine and they will spin, if not the cam/lifter is probably wiped and/or the adjustment is way too tight.

Bottom line to all this is you have something wrong in there and you have to take the intake manifold off to get to the lifters at the very least, Once there you can see the cam and determine what the lobes look like. Good luck with it...

60