Two Bent pushrods and valve keeper/spring retainer issues.

[NoNameYet]

This motor has run 20,000 miles on the same setup. Torn down and checked after sitting for some years. Now has lost and bent 2 chrome moly push rods on the same cylinder and dropped the lash caps after a few minutes' test runs on the stand. Taking the rockers off and noticed that the valve keepers are sinking into the retainer taper to the point that there is hardly a gap between the keepers on the exhaust side. I don't recall it was like that when assembled a week ago. On the other head all looks normal. Heads, dual springs , keepers and retainers are the ones that came with these Bugpack Street Eliminators.

One more thing I noticed is that the lash on the offending valve was too loose when reinstalling the rockers and good push rods from the other side to investigate. I'm sure that when setting them it was not loose, even though I remember seeing it funny that the adjuster was a couple of threads backed out compared to all the others. But I did check that push rod was in the adjuster cup before proceeding. (I might have missed seeing that?).

I actually suspect that lash cap was floating on the oil film on the tip of this valve, preventing it from properly seating on the valve tip. This in turn might have given me a false feeling that the setting was right. When I ran the motor that oil film probably got spitted out under the running load resulting in the loose lash I see now (about 0.80mm). Could this be?

Could it be the cause for the dropped lash caps and dropped and bent push rods?

Do you see any relationship between this and the keepers sinking into the retainer taper?

[dyno don]

  Hello there "newbie",  Bent pushrods are an example of too much tension somewhere in the valvetrain. This can be a result from keepers not interface matching in the keeper grooves. I have seen many valves that have sunken into the chamber and or broken as a direct result from this. Many companies that make one product doesnt mean they dont have another facility or vendor that makes the "other" parts, hence variable product control. My suggestion to you would be to disassemble the top end and take off the heads for inspection. Set your parts aside in an orderly fashion and take the time to inspect each and every valve and their perspective grooves. Now take the keepers and put them on the valve grooves and check to see if they are "touching" . This is more common that not if they are as I suspect. If this in fact is true in your situation, you will need to bench grind flat the keepers for a better interface fit, so they are not coming into contact with one another. Be sure to check all the retainers for any unusual anomalies that would indicate a bad retainer which would allow this to happen as well. I suspect that your valve grooves were compromised as a result from improper valve keeper interfacing. This would allow for the valve to "sink" or drop down, and it sounds like you caught it in time before it destroyed EVERYTHING. A little tip on lash caps/ The ONLY lash caps that should be used are hardened caps that have close interfit with the top of the valve. I have seen a lot of after market caps not last and can be the culprit of top end problems leading to catastrophic end results. I usually "peen" or tap the lash caps onto the tops of the valves to "seat" them in as they should be firm and not loose. The other possibility is if you have a bad seat in the chamber. Look at the chamber very close and check to see if the valve seat has shifted,cocked, or if the valve has been bouncing on the seat and destroying the valve job as a result from the keepers, retainer, or insufficient spring pressure. I wish you well and I hope some of this information will help you in your quest for a better understanding of your issue at hand. Keep everyone posted with your update findings.  Peace Out/Dyno Don            www.dynodon.net

[NoNameYet]

Thanks Don for your reply. This is a motor I built over 10 years ago, mostly new parts (First real hi-po build).  Never had problems running it daily for over 20,000 miles over about 4 years. 1915cc, CW crank, long duration cam on high ratio roller rockers, big valve BP Street Eliminator heads with Chevy style dual springs, running 48's that was a blast to drive. Then set aside when I decided to restore the car that was never completed. Torn down for a refresh and check after sitting for some years. No issues found, lightly lapped valves in the refresh process, cleaned and checked all and reassembled (supposedly) meticulously by myself, never touched by anyone else. Then this has happened.

I am mainly blaming myself for the cause since as I said earlier I had noticed that cylinder 4 exhaust adjuster was still a couple of threads further out when set on reassembly and compared to all the others (it only took like 1/8th of a turn). I did check that the pushrod was in the cup though it might have been my bad not seeing something fishy. After the worst happened I did take the rockers from that side off, did not change any adjusters settings at all, reinstalled the rockers from the 3-4 side using the still good pushrods from 1-2 side, and to my horror I find that there is that 0.8mm lash gap on the no. 4 exhaust ! All the others (7 of them) were fine with zero gap (Chromoly pushrods). That is when I started suspecting the lash cap on that valve not having seated properly on the tip on assembly. Something I MUST have done wrong there on that particular adjuster setting, otherwise from where would all that gap come from? Cam lobe still measures correct lift at valve. No issues on the other valve that shares the same lobe. Also checking with a steel rule edge the valve tips are still at the same height, but this particular retainer does sit higher than the other 3 which corresponds to the difference I see when comparing the deeper depth of the keepers in this retainer to the others. This suggests to me that the keepers are still at the height where they should be but the retainer has in fact moved higher up in relation to the valve tip, grooves and keepers on that valve. Kind of the retainer taper is wearing out and widening letting the retainer slide higher. There still seems to be a minimal gap between the keepers of this valve, but not as  much as clearly seen on the other valve keepers. It also leads me to think that this is a sign of a failing retainer more than anything else. I'm not trying to blame the part or the manufacturer. I'm trying to understand what, how and why it all happened, and trying not to repeat or having the same thing repeat itself.

Tomorrow I'll start by pulling the springs out with the head still in place, and check the keepers as you suggest. I might even try switching keepers and retainers as sets between valves to see if this problem shifts with the parts. Still can't see any relationship at this stage between this keeper/retainer problem and the loose lash FACT. I want to know if one caused the other.

Please excuse the long post, but hopefully it explains things better now that I am calmer.

[dyno don]

I recently tore down a similar engine that experienced almost the same conditions as you explained and could not find anything wrong other than the lash caps were aftermarket  and wiped out the tops of the valves. In your case this could be the problem or valve train fatigue from miles driven. If you logged in some 20K miles with early production heads,and (with chevy springs,ratio rockers, big cam), they could have had premature metalurgy problems from the foundry which I have seen a lot of. Heat cycling can be the worm in the apple syndrome as with most after market heads, and although you logged 20k miles perhaps the metal has met its life cycle. Kudos to you for a good enough engine prep and assembly to reach 20k miles and I KNOW you drove the HECK out of it,(dont we all?) The sinking of the valve into the retainer sounds more like the seat sinking than anything else. All things being what they are, you drove a fair amount of miles with a highbrid VW engine.  Keep smiling my friend, you still own a VW.  Good Luck, Dyno Don

[spanners]

Hi, just some info on a similar problem to yours from which you may be able to extract some data, but your motor was only test run at low revs?  could the retainer keeper problem have been overlooked on the re build ?, i fancy the problem was already extant,as how could that damage occur on a test stand at modest revs and load and a short test period?  ive come across the keepers sinking into the retainer fairly often, but it was due to too weak on the nose v/ spring pressures, it was accompanied by 'knocked down' valve guides as the valve gear orbited the cam nose, the guides had sunk to the guide boss top, which in turn had witness marks from the retainer hitting it, all this contact had jarred loose the taper interface and worn the retainer, this then rose up the keepers and further compromised the spring pressures, no clue is evident when this happens as the seated pressure can be enough to stop valve bounce, you only know its going on when a valve breaks at the grooves and goes down to it and the motors death. as Don says, you still have a motor, hope the info helps anyway.
best regards Johnny.

[Dominick Luppino]

Hi, just some info on a similar problem to yours from which you may be able to extract some data, but your motor was only test run at low revs?  could the retainer keeper problem have been overlooked on the re build ?, i fancy the problem was already extant,as how could that damage occur on a test stand at modest revs and load and a short test period?  ive come across the keepers sinking into the retainer fairly often, but it was due to too weak on the nose v/ spring pressures, it was accompanied by 'knocked down' valve guides as the valve gear orbited the cam nose, the guides had sunk to the guide boss top, which in turn had witness marks from the retainer hitting it, all this contact had jarred loose the taper interface and worn the retainer, this then rose up the keepers and further compromised the spring pressures, no clue is evident when this happens as the seated pressure can be enough to stop valve bounce, you only know its going on when a valve breaks at the grooves and goes down to it and the motors death. as Don says, you still have a motor, hope the info helps anyway.
best regards Johnny.

My exact thoughts, possibly valve float.

[Jim Ratto]

Hard to say without taking head down and pulling valve out/inspecting. Unless the grooves in valve stem widen out, the keepers shouldn't move in relationship to stem... if they have 'sank' then, in relationship from stem tip (where lash cap goes) then the grooves are probably wiped out. OR the retainers have pulled through at ID at lower edge, destroying the wedge. If the grooves wallowed out, it's usually a symptom of keepers not being set up as a locked interference fit, meaning when you look down on them from end of valve, they are meeting, or touching. Anytime HD springs or faster ramp cams are run, it's a good idea to check fit of the keepers to the valve stems and make sure the OD of the stem is keeping the two halves from touching. You can use a bench grider or coarse belt sander, or even a good hand file to do it. if the retainers pulled through, it's like Dom and others said, probably valve float. I'd check to see if valve is bent too? How much piston to valve clearance are you running? is the excess valve lash after the pushrod bent or before? Is your geometry on, so pushrod is traveling in same plane as valve stem @ 50% lift?
Good luck, it's rough when things like this happen, cause a guy to lose sleep for sure.

[NoNameYet]

Pulled head, no sinking seats and valves, no loose valve seats or any signs of shifting as far as I can see. Only number 4 exhaust retainer and keepers show signs of wear where they are in contact with each other. All the rest still show machining marks and the black coating. No contact between valve and piston on the problem number 4 exhaust. Valve is free to slide up and down the guide, rotates freely, checked rocking and it's just the same as the others. Rolled valve stem on the table of my mini mill, with no signs of stem bend, though I will check it on a high quality surface table at work tomorrow along with checking for any stretch which I did not check with instruments yet although it does sit at the same height as the others at the tip when checked with a straight edge rule. Spring height measures the same as others too. Keeper grooves check out OK when checked with the keepers from other valves, the damaged pair of keepers sort of bind on all valves, but all other keepers are a snug fit on the number 4 exhaust valve.

There seems to have been some contact between the keepers and the top of the valve guide. Still not sure if I must replace the valve due to this.

Can you guys think about some other check I might have missed?

All points cause to be the loose lash on the number 4 exhaust lash setting. I'm almost convinced the lash cap was unseated and probably floating on a drop of oil when setting lash clearances. My bad decision not to take parts off to check when I noticed the adjuster further out from all the others.

I'm hopefully now a little wiser and definitely poorer.

[spanners]

ahh, good info, now were getting somewhere, so the keepers HAVE hit the guide as i suggested, this MAY indicate a tired spring on that no 4 exhaust, probably the heaviest valve also, but not always,depends on the brand,, the v/s  life is over at the milage you quoted anyway, so a new set is required,  then the lash cap fell out and the p/r slipped onto the edge of the cup, the valve normally hits the piston  at this point, but theres no sign of this??  so  now the thing is, how did the p/r's get bent then,?..

As to replacing the guilty valve, yes certainly, it will be stressed at the lowest keeper groove, it wont break at a co-operative time when idling in traffic, it will break at high revs with the end result we all know about, cry once as they say..

[Big Power]

From what you are saying, I would say you experienced a valve float condition. Remove the spring that had the issue and see what pressure it has at installed height and also open pressure.

[NoNameYet]

Pat and others, I think you are either missing or ignoring the fact that the lash was set too loose on that valve. If you are ignoring it can you please explain why do you feel it was not the original contributor and was not an issue? If you missed that I mentioned it in my 1st and 2nd posts.

[spanners]

i see it thus so far, A two minute no load test stand run wont have cause the retainer/keeper interface wear you mentioned, it must have happened earlier.
reset the valve gap to as you think it was when the damage happened and try to replicate the lash cap falling out by cycling the engine by hand, if that conclusively  did happen, then the pushrod could come out too the edge of the cup, as i said earlier,  then actuate the rocker on the cup edge giving excessive lift, but there should be contact marks on the piston from the valve, how else would the push rod get bent? and then what happened with the second bent push rod you mentioned?

[Big Power]

Pat and others, I think you are either missing or ignoring the fact that the lash was set too loose on that valve. If you are ignoring it can you please explain why do you feel it was not the original contributor and was not an issue? If you missed that I mentioned it in my 1st and 2nd posts.

I didn't ignore anything in what you said but after that remark, I'm ignoring you now

[K-Roc]

Pat and others, I think you are either missing or ignoring the fact that the lash was set too loose on that valve. If you are ignoring it can you please explain why do you feel it was not the original contributor and was not an issue? If you missed that I mentioned it in my 1st and 2nd posts.

I didn't ignore anything in what you said but after that remark, I'm ignoring you now

Would have loved to see the reply before you edited it !   

Parts are cheap, take it apart check everything and replace what you don't trust..........

[NoNameYet]

I only edited some spelling or punctuation or added some portion most probably. Surely nothing offensive or unpleasant. It was a couple days ago and honestly I don't remember such irrelevant details. Mods can probably check that if in doubt.

I have not worked on it since, too busy with the job that pays the bills this week.

[NoNameYet]

In the meantime I bought some parts I'm surely replacing like the spring retainers and valve keepers, a new exhaust valve, new CrMo pushrods, new adjusters and some other small stuff.

[NoNameYet]

i see it thus so far, A two minute no load test stand run wont have cause the retainer/keeper interface wear you mentioned, it must have happened earlier.

Everything was being hammered due to the loose lash I believe, and that was from the very start. First time running a stinger (too loud for me) and I must have missed the clicking sound. The valve tip shows some wear too.

reset the valve gap to as you think it was when the damage happened and try to replicate the lash cap falling out by cycling the engine by hand, if that conclusively  did happen, then the pushrod could come out too the edge of the cup, as i said earlier,  then actuate the rocker on the cup edge giving excessive lift, ...

The push rod did at some point ride on the edge of the cup, the cup shows that clearly. The shim and washer at the end of the rocker shaft and the rocker bear some push rod marks too, so there was excessive lift at some point. Then I found the push rod end wedged between the rocker box side and the rocker shaft end.

but there should be contact marks on the piston from the valve, how else would the push rod get bent? and then what happened with the second bent push rod you mentioned?

There are definitely no contact marks between piston and valve. I saw that and what it looks like, and can see it even if it was slight. I even took high resolution and high magnification photos of the piston crown and examined them on a 24 inch screen at 100%. That would have shown even a 1mm mark at a much larger scale on screen. I consider myself lucky about that. Running 8.6:1 compression with non fly cut heads may have saved me.