boxtruckcamper

Hi all-

This is my first time owning a chevy. I have a 5.7 v8 in my 96 g30 box van. When I bought it, I thought I was going to need to replace the whole engine. But as I've been tinkering, I'm starting to think I might be able to save this engine after all.

Here's the situation: cylinder 2 has low compression (30 psi). All the other cylinders are good, over 150 psi. I did a wet compression test and it stayed at 30 so I'm guessing its a valve train issue. When it's running, the engine makes a clattering noise only on the top end at that cylinder. It sounds a lot like lifter tick to me, and it doesn't go away when the engine is warmed up. It's consistently ticking at idle, when revving, and when letting off the throttle.

Are these problems related? Is it possible that a bad lifter could cause low compression? Or is it possible for a stuck valve to cause lifter tick? I haven't been able to find any forums or videos that answer this question.

Here's some other context about the overall state of the engine. I already replaced spark plugs, wires, distributor cap and rotor, and the ignition system is running great. The spark plug in cylinder 2 was shot when I replaced it. I tested fuel pressure and it's good. The check engine light is on, but the only code that comes up is for an oxygen sensor circuit. No misfire codes. There is a pretty substantial oil leak at the base of the distributor where it goes into the intake manifold. I've been waiting to address that until I know if I need to do a full engine swap. In the meantime, I'm just keeping the oil topped off.

Any help is super appreciated!

oilcanhenry

I'll bet you have a piston or ring issue myself. 30 PSI means that the cylinder is not holding much pressure at all. It could be a valve issue, but I doubt it. Be willing to bet your piston itself is the problem. I don't like indicating this to anyone then you do, but that is indeed the issue, IMO.

boxtruckcamper

Could be, that's what I was trying to rule out with the wet compression test. I'm planning to do a leak down and I can update this after I confirm where I'm losing compression. Do you have any ideas about the lifter noise? Could that be related to a valve problem, or is it just a coincidence to have these two problems in the same cylinder?

ray caldwell

Have you adjusted your valve lash? My 92 had slack lifters when I got it. Ran alot better after I got movement out of it

boxtruckcamper

I haven't, I'll add that to my list. Any tips for me before I start taking things apart?

boxtruckcamper

Update: A leak down test revealed the intake valve is stuck open, next step is taking the valve cover off and checking the adjustment, push rod, rocker arm, etc. Wish me luck!

oilcanhenry

Yeah, the intake valve being stuck open would do this. It's not often that this occurs, however, but at least some headwork is all that needs to be done. Thing is, however, was how it got stuck that badly. Not getting enough oil would do that, or carbonation. I'd recommend a new lifter. Possibly a new push-rod and rocker arm as well, depending on your judgment. Might be even a new or rebuilt head, but I'll leave that up to you.

boxtruckcamper

Hopefully I can avoid a head rebuild. Could a bum valve spring lead to lifter noise? I haven't had a chance to take things apart yet, mostly I'm wondering if I have two separate issues (stuck valve and noisy lifter) or if they are really the same issue. Guess we'll see once I get under there and take a look.

oilcanhenry

I suppose or think the lifter is bad. How do the valve seals look? Are they hard yet? Might at least replace the one on your valve.at least.

I'm also kind of worried about the valve guide. It's likely got resin deposits left by oil caught in between the valve and valve guide.

William Kisselstein

If you can find a borescope you can pull the plug and have a look inside. There are some as cheap as $20 but no idea how good they are. #3 has to be up under there so probably a pain to get to. and of course taking the valve cover off will answer some questions too. Maybe you can tap it with a hammer and free it up.

It probably makes noise because with the valve stuck open the rocker is loose.