I am in need of some help. The 1999 vortec 350 in our suburban has a loose rocker arm and 0 compression in that cylinder. I tried a new locking nut and tightening it down while the engine is running but it seems I cant tighten it enough. Could we have collapsed a lifter? Any suggestions will be appreciated. Thanks

 

what cylinder is it on?

 

3rd one back on the passenger side.

 

How did the push rod look? It could be bent. Also that engine has a roller cam in it.

 

You say you have no compression on that cylinder. that makes me think its not a collapsed lifter if the lifter is collapsed the valve would not open there for you would be building lots of compression. sounds like you may have bigger issues than a loose rocker. get that cylinder on tdc compression loosen the rocker nuts until you can move the push rod up and down so it actually isnt tight on the lifter or the rocker. tighten the nut down until the slop is gone then go 1 complete turn that is how they are supposed to be adjusted. sounds like you may have it to tight and thats why you are not building compression.

 

Straight.

 

The compression test was done before I removed the valve cover. So the rocker arm was loose at that time. From what I understand, the cylinder should have compression even though the rocker arm is loose because the valve spring is still tight. So maybe a bad piston/broken connecting rod?

thanks for the replies. I sure do appreciate it.

 

Any engine noise, rapping etc?

 

I can hear the clicking of that rocker arm but nothing else really. When I give it a few more rpm's the clicking speeds up but that is about it.

of course it is shaking and barely running while at idle. add some rpm's and it evens out.

 

It could be a burned valve. How many miles on the engine? Is it using coolant? It could be a lifter that blew apart, I have seen that happen, just not that often.

 

Easiest thing to do is pull the intake and look at all the lifters. Get the updated intake gasket set and do not use the rubber end seals for the intake. Use a sealer called "The Right Stuff".

 

The engine has 160,000 mi. We have only owned it for 4 months so the history of it is vague.

It is not using coolant and has not overheated. Running it with the valve cover off I can see the Valve spring going up and down.

 

crate engines are fairly reasonable if you do determine that the engine is damaged such as rods or pistons it may be a better option with that kind of mileage.

 

Thanks for the replies.

 

If you have access to a bore scope get it and put it through the spark plug hole and see if you can see what is going on.

Things to ponder- if there is no compression then something is being held open or is catastrophically damaged. Burned valve, burned hole in piston, etc.

Either way to me it sounds like that head has to come off.

Post what you find, we will continue to help you out.