Lost Two Gen 3 LS Engines in my 1986 C10 2WD

[Ricko1966]

Thing is that I watched cylinder #2 intake valve closing very slowly when turning over after the damage had occurred. That's what led me to believe it was valve to piston contact.

The other thing that strikes me as odd is that it ran good when I shut it off. It's the next time I went to start it, it turned over super easy, so either the damage occurred as I shut it off (which doesn't coincide with injectors filling the cylinders while running) or the starter damaged the motor? Just doesn't seem likely to me

See if all the pistons are parking at the same height,check through the spark plug holes.

 

[Ricko1966]

Here's something else to think about. When you tag a valve it's usualy an exhaust valve,because the piston is chasing the exhaust valve shut. The intakes are opening as the piston is moving away from them. I'd takethat engine apart and investigate. At the least I'd see if all the pistons are parking at the same height and pull the rockers on the low cylinders and manually open the valves feeling for binding opening and watching for binding closing., and usually a bent valve will park at a different installed height.

 

[1lejohn]

Are sure neither of these engines are DOD? I'm seeing or imagining I'm seeing a pattern in compression between DOD cylinders.

Thats what I posted earlier.

 

[Ricko1966]

Thats what I posted earlier.

When these things get 10 pages deep,I don't read every post but it is suspicious that the low cylinders are the cylinders that are DOD on DOD engines. It's also suspicious that #2 has had zero,90 or 150 lbs depending on which post you read.

 

[shortboxin]

When these things get 10 pages deep,I don't read every post but it is suspicious that the low cylinders are the cylinders that are DOD on DOD engines.

No one ever answered my question when the DOD question was asked and that was this, "The 2004 4.8 had 706 heads and the 2002 5.3 had 862 heads. Were those used on DOD engines?"

 

[shortboxin]

It's also suspicious that #2 has had zero,90 or 150 lbs depending on which post you read.

You're not aware of the timelines on everything, but when the engine was still impacting (making contact that I presumed to be a valve) I was getting 0 PSI on cylinder #2. When I attempted the second compression test weeks later but on all 8 cylinders, I only got 90PSI on the first attempt. I then gave it a second try once I had checked the remaining cylinders and it suddenly was at 150PSI.

Thing I can tell you for certain is that one valve on cylinder #2 was slow to close when I turned it over with the valve cover off a couple of weeks ago. In other words, it was open when it should've been closed which is where all of the compression was going and why I believe the valves made contact.

 

[Ricko1966]

No one ever answered my question when the DOD question was asked and that was this, "The 2004 4.8 had 706 heads and the 2002 5.3 had 862 heads. Were those used on DOD engines?"

You told us on post 23 it's not a DOD engine. This novel is 5 pages deep,and I'm not going to read every word,or even every post. Even if I did, I do not know everything about every engine chevy ever made by year and displacement. I assumed it was not DOD because you said it wasn't.

 

[shortboxin]

I'm basing non-DOD on the years of vehicles they were pulled out of. I understand there's a lot of posts, but I posted my response right below your question. You probably didn't make it back for a few days. No worries.

As for further teardown, it's gone to someone else already, but I will ask him what he found.

 

[shortboxin]

UPDATE:

Put in a 5.3 from a 2004 Tahoe. Replaced the chain and gears, oil pump, and front and rear seal. I am using a different computer just in case.

1. Flushed out fuel tank and fuel line as I knew the gas was questionable last October when I started all of this. Put in fresh gas and flushed line again further.

2. Tested the injectors before attempting any startup by turning the rail upside down with injectors in it and pressurized the system. Let it sit for 2 hours, never saw any leaking. Turned key on one more time and double checked, no leaking.

3. Started up and drove with no obvious issues. De-pressurized fuel rail and checked to make sure that there was no power on the injectors with key off. Disconnected negative battery cable.

4. Waited one day and started and drove again with no issues. NEVER HAD A SECOND START ON THE OTHER ENGINES AFTER DRIVING. THIS IS A FIRST! De-pressurized fuel rail and disconnected negative battery cable.

Will be starting it again tomorrow after work and follow up with de-pressurizing the fuel rail and disconnecting the cable. The following attempt will be without de-pressurizing the fuel rail, but still disconnecting the cable and will update again Saturday night.

 

[Frankenchevy]

In the future, a wet compression test after a normal compression test can help you tell if it’s rings or valve timing/seat sealing.

If the compression doesn’t go up on a wet test, it leans more towards a valve issue.

 

[chief_shotts]

Small block swap it.














Sorry, had to.

Same thought came to mind

 

[shortboxin]

In the future, a wet compression test after a normal compression test can help you tell if it’s rings or valve timing/seat sealing.

If the compression doesn’t go up on a wet test, it leans more towards a valve issue.

I'm certain that the second engine was bent valves. I witnessed cylinder #2 sticking open while turning over. Same fail mode on first engine, so likely the same issue.

 

[shortboxin]

No interest in small block. I've had new Edelbrock carbs die here in AZ in 3 months from gas drying up and varnishing the jets. Besides gas mileage isn't great.