Driver's side Cylinders 50-60 PSI, Drinkers side 130-140 5.7L 350 1986 K10 Suburban Crate Engine

[beastmazter]

Hello Everyone,

Picked up a 1986 suburban square body goodness from a guy off marketplace. He dropped a 350 crate engine in the truck that he pulled out of another vehicle. The engine supposedly has about 3500 miles on it and has towing cams. Those are the details I received on the engine. I picked up the project after the engine was dropped in, still needed wiring, plumbing and lots of other odds and ends. The body hadn't been on the road in about three years, I am actually not sure how long the engine sat unused. I clearly asked great questions before buying.

It now runs and drives, can take it around the block and it runs decent. Lots of blows by, oil coming out of distributor tube (probably not the technical name) oil coming out of valve covers. New PCV valve on Drinkers side, Breather on driver's side. Preformed compression test to diagnose issue.

Cylinders 2-4-9-8 130-140 PSI
Cylinders 1-3-5-7 50-60 PSI

Need to pull heads ad inspect, currently hoping for something simple like a bad head gasket. Any other ideas or things to look for?


Thanks in advance!

Michael


Some pictures

Plugs I pulled to do compression test, looks like she's running hot. Left hand side, from bottom to top are Cylinders, 1357.

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Engine

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A beauty!

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[Ricko1966]

Pressurize each cylinder one at a time with compressed air,I'll bet you 1 or 2 cylinders are going to send huge amounts of air out of the oil fill tube. That's going to wmean,most likely a hole in a piston shattered rings or broken ringlands. If you are going to do it lmk I'll walk you through the test,but not going to write it up now if you don't need the info.

 

[Rickf]

The proctologist cameras on amazon are pretty reasonable, plus you can snake it down a spark plug hole. If you make the plunge, make sure it has a stiff but flexible wand, not the flaccid type that is used with a cell phone. Good luck with your probing.

 

[beastmazter]

Pressurize each cylinder one at a time with compressed air,I'll bet you 1 or 2 cylinders are going to send huge amounts of air out of the oil fill tube. That's going to wmean,most likely a hole in a piston shattered rings or broken ringlands. If you are going to do it lmk I'll walk you through the test,but not going to write it up now if you don't need the info.

Thanks for the suggestion, probably the next best course of action. I have a broken air compressor at work I was thinking of turning into an air tank, so I could do the leak down test at home. That or I was just going to rip into the engine and take the heads off, probably overkill without more info, but figured it's pretty likely at this point that I will need to pull the heads. Unless it's something silly like valve adjustments.

The proctologist cameras on amazon are pretty reasonable, plus you can snake it down a spark plug hole. If you make the plunge, make sure it has a stiff but flexible wand, not the flaccid type that is used with a cell phone. Good luck with your probing.

I do need to get me one of these, in this case I will probably just take the heads off. I have already spent too much money on this project, and I have time this weekend to tear it apart. Sure would be nice to have a peak with a camera, though.

 

[Ricko1966]

Thanks for the suggestion, probably the next best course of action. I have a broken air compressor at work I was thinking of turning into an air tank, so I could do the leak down test at home. That or I was just going to rip into the engine and take the heads off, probably overkill without more info, but figured it's pretty likely at this point that I will need to pull the heads. Unless it's something silly like valve adjustments.


I do need to get me one of these, in this case I will probably just take the heads off. I have already spent too much money on this project, and I have time this weekend to tear it apart. Sure would be nice to have a peak with a camera, though.

The camera won't show broken rings or ring lands and if you have huge blowby it is not valve adjustment.

 

[beastmazter]

The camera won't show broken rings or ring lands and if you have huge blowby it is not valve adjustment.

I just want you to give me good news Ricko, stop ruling out the easy fixes. hahaha

 

[beastmazter]

@Ricko1966 If it were a hole in a piston or bad rings, would that cause all 4 cylinders on the one side to have low compression? That's the part that is confusing to me, is how all 4 have low compression. Wouldn't that impact the compression on the bad cylinder and not the rest?

 

[Ricko1966]

Pressurize the cylinders, I didn't read close enough didn't notice you had one whole bank down. But I s

 

[Ricko1966]

Pressurize the cylinders, I didn't read close enough didn't notice you had one whole bank down. But I s

Okay the pop-ups are so bad I couldn't finish replying so let's try again. A whole bank down and big blowby my guess would be one bank leaned out,due to an intake leak or a plugged jet so they either melt holes in pistons melt the top ring land or shatter rings or ring lands when they start detonating from being hot because they are lean. I maybe wrong,I hope I am but it's the first thing I'd check.

 

[beastmazter]

I will see what I can do to get a compressor or air supply of some kind. Thanks for the advice. If that doesn't pan out, I will probably rip the heads off to see what I find and hope I don't regret not doing the leak down first.

 

[Ricko1966]

Okay since it sounds like you're going to attempt it, pull the valve cover and loosen all the rockers on the offending side,put the valve cover back on. Put a rag in the tailpipe, put a rag over the carbureator,take off the oil cap and radiator cap and put rags there.Hook your compressor to a cylinder and hit it with pressure watch and listen. Air through the carbureator is an intake valve issue out the tailpipe is an exhaust valve issue,through the radiator filler its a cracked head,cracked block,blown head gasket,through the oil filter it's pistons or rings 99 percent of the time. Just for fun a new service writer was watching me with big eyes asking Dave what was I doing? Dave said he's blowing air in the cylinders if that comes out of the tailpipe it needs an exhaust valve if that rag blows off the throttle body he needs an intake valve,and if the rag blows off the valve cover he needs a new oil cap. This tool looked at Dave and said Really?

 

[Ricko1966]

I will see what I can do to get a compressor or air supply of some kind. Thanks for the advice. If that doesn't pan out, I will probably rip the heads off to see what I find and hope I don't regret not doing the leak down first.

What's wrong with your compressor? Is it separate motor and pump or? I know some dirt cheap hacks for diy get by air compressors. Post a p8c evennifnits a just a similiar model,and what doesn't work.

 

[beastmazter]

HAHAHA that's hilarious!! I love this test, I will try to get my friend to bring the air compressor that I gave him over to my house. I sold my house and gave all my tools to friends, so I could borrow them when needed. I may be able to convince him to load it up and bring it over, it's a big boy, though.

 

[beastmazter]

I have a broken one at the shop, it's a small craftsman but won't build pressure past 30psi. I tore it apart to see if I could replace a valve etc. but it's cheaply built and didn't have anything replaceable to fix the issue. Was going to use our good compressor here to pressurize it and use it as an air tank, but I don't have the parts on hand to make it happen. Probably easier to borrow back my good compressor if I can convince my friend to load it up.

We threw out the compressor part and kept the tank. It was a cheapo unit that we didn't care to fix.

 

[Ricko1966]

I have a broken one at the shop, it's a small craftsman but won't build pressure past 30psi. I tore it apart to see if I could replace a valve etc. but it's cheaply built and didn't have anything replaceable to fix the issue. Was going to use our good compressor here to pressurize it and use it as an air tank, but I don't have the parts on hand to make it happen. Probably easier to borrow back my good compressor if I can convince my friend to load it up.

We threw out the compressor part and kept the tank. It was a cheapo unit that we didn't care to fix.

I wanted a pic so I know what I'm dealing with. If it's just one of those little hot dog compressors or pancake compressor with pump and motor as one unit,you can rob a compressor from a junk refrigerator or a/c unit. It will be your pump and motor hopefully you still have your pressure otherwise you are the pressure switch watch the gauge flip the switch. Use an automotive fuel filter on the inlet line as your air filter. Separate pump and motor situation grab a junk yard York style a/c compressor use switched 12v to the clutch or tack weld the clutch they're good for at least 150lbs.