'90 5.7L missing since new

droptail · July 10, 2004

The #8 plug loads up with oil. Had it fixed under warrenty twice. First time they pulled the heads and rebuilt them with seals (new valves too) but that didn't fix it. The second time they said they re-ringed #8, of which I doubt at this time. They said the ring gaps were lined up and sucked oil. What do you guys think? Has always run great, just rough at idle.

Are Vortec heads a typical upgrade when rebuilding for smog legal?

quadhauler · July 10, 2004

I suppose the ring gaps could have been lined up..... This is a 1990 truck, when did the warranty work get done? It seems to me that if they had to go into the truck when new and do a head job, they should have just replaced the whole thing. Thats what I would have expected anyway. If this is a warranty on a rebuilt motor, it could be anything. Too loose an overbore, ring problem, or some remaining scoring from the previous bore. How many miles are on it now?

My 93 had a headgasket problem on the 305, and no matter what I did to it... Vortec, new heads or whatever, it would always be a 305. I put in a Caprice replacement motor (about $1600). Its a 5.7, has a roller cam and a one piece rear main... not a Vortec, but then I didn't have to spend $$ on expensive TBI vortec intake and HAVE to do ECM mods...

snoman · July 10, 2004

I really doubt the ring gap thing. Yes you stagger then when you build a engine but they will float around in there with a few 100 million trips up and down the bore as there is nothing to keep them in place.

02 Silverado Z71 · July 10, 2004

Go about this the right way, and stop guessing. Perform a cylinder leakage test, and resolve this problem.

snoman · July 10, 2004

I would pull head of and inspect cylinder walls and head valve guides.

02 Silverado Z71 · July 10, 2004

snoman...

Why in the world would you start tearing an engine apart BEFORE you do the basic tests on it??

DO A CYLINDER LEAKAGE TEST FIRST

snoman · July 10, 2004

snoman...

Why in the world would you start tearing an engine apart BEFORE you do the basic tests on it??

DO A CYLINDER LEAKAGE TEST FIRST

It has a re-occuring problem with number 8 cylinder as poster said. This is not a new problem. Doing compression test now is a waste of time. He either has badly worn or improperly reamed valve guides from the factory or possible a broken ring. Head needs to come off and fix it for good. It may have a burnt valve too. Regardless whether is is rings or guides or valve or even the head itself, the head needs to be removed and a compression test is a waste of time. If this was a new problem I might go along with a test but in this case it will have to come apart. Head need to be checked for creaks or casting holes too. Anything else is wishfull thinking as this is pretty cut and dried here, sorry.

02 Silverado Z71 · July 10, 2004

Snoman...

You are reading this ALL WRONG...

A compression test is NOT a cylinder leakge test. Here's how a cyl leakage test works...

Get the affected cylinder to top dead center with both valves closed. Install threaded adapter into spark plug hole. Install pressurized air(shop supply) into cyl leak tester. Adjust incoming pressure to certain spec(chart comes with tester)

You will now have a result of how much leakage is within the cylinder.

Now, you go to the chart that comes with the tester to determine what your problem area is. When the cylinder is pressurized with shop air, you can also LISTEN to where the air is escaping. Such as :

rings: remove oil fill cap and listen

exhaust valve/guide: hear at tailpipe

intake valve/guide: hear thru throttle body

snoman · July 10, 2004

Snoman...

You are reading this ALL WRONG...

A compression test is NOT a cylinder leakge test. Here's how a cyl leakage test works...

Get the affected cylinder to top dead center with both valves closed. Install threaded adapter into spark plug hole. Install pressurized air(shop supply) into cyl leak tester. Adjust incoming pressure to certain spec(chart comes with tester)

You will now have a result of how much leakage is within the cylinder.

Now, you go to the chart that comes with the tester to determine what your problem area is. When the cylinder is pressurized with shop air, you can also LISTEN to where the air is escaping. Such as :

rings: remove oil fill cap and listen

exhaust valve/guide: hear at tailpipe

intake valve/guide: hear thru throttle body

It is oil fouling plug and is a REOCCURING PROBLEM which you seem to miss here. It could check fair to could and still have bad valve guides duh.... IT has never been fixed correctly from day one because it was never properly insepted and you never will either without a proper visual inspection of that bank. It is just plan dreaming and I can tell that you have not dealt first hand with problems like this. Experiance tells you when to tear down and when to look elsewhere and this is not the time to look elsewhere or for other causes. Once again, if this was not a reoccuring problem, I would go for test but it is not the case here. There is a track record here. Give me about 5 minutes with head of and I will tell you EXACTLY what needs to be fixed!

02 Silverado Z71 · July 11, 2004

...or he can just bring it back to the dealer and THEY can fix it; maybe for free. They did have this engine torn down twice: should be a no-charge fix.

OUMike · July 11, 2004

...or he can just bring it back to the dealer and THEY can fix it; maybe for free. They did have this engine torn down twice: should be a no-charge fix.

On a 90' model they'd probably look at him like he was