just finished head gasket now the valve keepers fall out?

[turbo_420a]

This is my probmlem in a nut shell me and my mechanic are lost... I bought my 08 nytro two months ago and as far as I know I blew the head gasket on my first ride because the fan relay was broke and it overheated. I diagnosed it as a head gasket and brought it in 1200$ and three weeks later I go to pick it up. He ran it through a few heat cycles and all is good with the head gasket, got to put it on the trailer and it drops a cylinder...we pull it back into the shop and diagnos that one of the keepers on two different valves have some how outside of the retainer and holding the valve open causing lose of compression. How is this possible he never touched the valves....never took the head appart just pulled off the head and replaced the gasket. So we tore it back apart put all the keepers back in and retainers and put it all back together not sure why it happened took it back out and ran it again and same thing happened somehow the keepers are fallingl out...has anyone ever heard of this happening...does it probably have to do with the valve shims or cups that cover them????

 

[rrxx-1]

Is he sure he has the valve timing set correct, so that a valve is not hitting a piston?

 

[5valve]

Is he sure he has the valve timing set correct, so that a valve is not hitting a piston?

Thats exactly whats going on.

 

[turbo_420a]

both times the timing was set and checked rotated manually so the timing chain tensioner could preload then the engine was rotated again timing was checked it was put back together and ran for a few minutes so the carbs could be vac synced and it purred like a kitten. then we test rode it ripping on it at high rpm for 10 minutes after that is when it started to miss and we determine the keeper was holding the valve open. So tore it back apart and reset everything resync throttle bodies and I ran smoothly like normal and once again after the ride is when the keeper came out. How is it possible for this to happen without internal engine damage. We were able to put keeper back in and reset timing and have it run good again doesn't make sense if timing was off it would have bent a valve and it would have been done?

 

[grizztracks]

Being new to you, do you know the history of the sled? When you pulled the head did you remove the cups on the valves, was the head surface machined, the two times it happened was it the same valves? Do you have broken valve springs? The springs are what hold the keepers in place.

Never heard of the Nytro engine having this issue.

 

[turbo_420a]

i now most of the history of the sled no major engine work, valves were not removed for gasket job and head was not machined and at inspection everything looked good as far as a broke spring he never removed them so I guess thats were we should start.....

 

[turbo_420a]

I cant believe that its coincidence that two springs broke or somthing unrelated to the head gasket job just happened to happen at the same time. its it possible that as a result of somthing he did I was able to over rev the motor and float a valve.....I was working it over quite good to make sure it was good before I brought it home. I think the highest rpm I seen was 8000 I think maby 8300 somewhere in that range...are these engines electronically limited to a certain rpm...

 

[grizztracks]

If I remember right the rev limit is set at 9400 rpms so you are well below that. The engine is designed to run safly up to that point without floating valves so if you are dropping a valve at a lower rpm there is a underlying problem that possibly could have resulted from overheating it. You didn't say if both time it was the same valves and if so was it specific to intake or exhaust? A head gasket replacement shouldn't have anything to do with the keepers falling out.

 

[turbo_420a]

it was two different valves same cylinder exhaust side.

 

[turbo_420a]

if in fact it is dropping a valve at a lower rpm what could that possibly be broken valve spring bad keeper are these motors known for weak springs

 

[turbo_420a]

ok update.....after taking it apart we again found that the second time it started running rought it was only a vacuum line that had came off the throttle body not another keeper falling out, so we pulled valve cover back off and Springs retainers and keepers all look good so now I'm trying to decide if its worth replacing them all just to be safe. what do you guys think I should do $250 for springs and retainers when mine look fine...the only possibility I could fathom is that when the cams were removed somehow I sprang stay depressed and the valve moved causing a keeper to fall out other than that don't understand how its possible for a keeper to come out while the engine running. even if it floats a valve somthing would have t return the valve up wile the spring stayed down...

 

[grizztracks]

When you float a valve the rpm's reach a point that the valve spring can't keep up and essentially floats. A weak or broken spring may float at lower rpm's and It only takes a split second to release the keepers. It's unusual to have the keepers fail on a stock engine so I'm wonder if you got some debris under the lifter or if somehow the pad shifted to the side and pushed down on the spring rather than the valve stem. I don't think I'd worry about it but if I was going to replace parts it would be keepers and valves on at least the ones that dropped.

 

[turbo_420a]

ok I think with over half my season spent in the shop ima chalk it up to a fluke and put the next few hundred miles on slow and easy and keep my fingers crossed and if ut happens again go from there. thanks for all the help..