Odd piston color

[jojo-munson]

Hey all, I pulled the heads off my 72 c20 with a 350 due to it blowing white smoke, bubbling in the radiator, and lots of milky gunk under the valve covers. So I figured I had a blown head gasket. When I got the heads off, my numbers 5 and 6 pistons are a different color than the rest. I'm assuming this is a side effect of the head gasket leaking and coolant getting in there. Is this anything I need to worry about? Or should I be okay with slapping the re-machined heads back on with fresh gaskets?

[BCOWANWHEELS]

You need to do alot of cleanning, straight edge block top, check for cracks... Theres a crack somewhere

[Artofdeath]

Yepp, you need to find the leak. Check the head gasket, see if you can find the path the coolant was taking to get into the cylinder. Could be more than one point of entry. Best case, it was the gasket, worst case, a crack in the head or block.

[Grumpy old man]

The pistons look different from the "steam cleaning " caused by the leak into those cylinders , Usually you'll only find it on one bank but with seeing it on opposing cylinders and the amount of sludge seen on the outside of the engine it probably is time for a rebuild ? Slapping fresh heads on a worn block will just increase blowby with a tight top and worn bottom end and result in blue smoke (oil) when reassembled . How many miles are on it ? Back in the day we considered any car or truck with 100,000 worn out ! I'd rebuild it if no cracks are found .

[scott123]

On the gasket where the off colored pistons are at check it thoroughly under a light. If there are odd wear patterns or cut patterns then it could have been the gasket alone.

If the heads are being re-done ask them to be checked for cracks.

The decks of the block can take a brutal beating but needs to be checked. Like posted above, clean the deck surfaces.

Use a straight edge, framing square, and slide it back and forth and top to bottom across the deck. It is about the best option with the block still in the truck.

Pull each piston up to TDC so you can clean them as well, especially the off colored ones.

Most of the time the issues you describe comes from the head or the head gasket.

Best of luck.

S

[100%Chevy]

The plugs from those cylinders should be the same color as the pistons!First sign of a water leak in the cylinder.
I'm guessing with it leaking on both banks,someone got the engine very hot!
Just did a top-end on my 454 because of a leak.I think it was .005 or less to be straight.
As said above,use a known good straight edge to measure to out of flat on the heads and block.Too much and you need to have them machined.
Mike.

[jojo-munson]

Thank's for all the advice guy's! The engine was supposedly rebuilt less than 30k miles ago, so hopefully the block is okay. Here are pictures of the gaskets themselves. There are a couple holes that look like they don't belong. I went and wiped down the surface of the block and couldn't see any cracks, but I'll go and clean it better after work. Need to pick up straight edge too.

[BCOWANWHEELS]

30k............ I,d down it to bare block. its been jack leged I bet

[Grumpy old man]

Before someone asks


Jackleg, adj., is a Southern adjective meaning inept, unprofessional, or dishonest. It is usually applied to members of a particular occupation. You do not, for example, want to take your car to a jackleg mechanic. The term dates to 1837.

[BCOWANWHEELS]

close enough I RECON

[jojo-munson]

Thanks for the jackleg explanation haha, always fun to have a new word to throw around. So just got a call from the shop, both my heads are cracked! I live in a small town with no real junkyards, so I might have to buy a pair online off of summit racing.

[scott123]

Odds are the block is fine. I'd check it with a straight edge.

If it was running when you pulled it down, again, odds are the bottom end is OK.

When water enters the cylinder in smaller amounts it is pushed out. If it were a deck problem it would be larger amounts.

Air will compress. Water will not. If it were larger amounts of water odds are a piston or piston wall would have given up.

I'd clean it up and put another set of heads on.

Clean and dry and torque in the correct order.

Looking at the gaskets, I would think they were torqued right up to the point the asshole puckered. Then a 1/4 turn.

The preferred method for most jack legs.

S

[weq92f]

So the jack leg would have known about the cracks and installed the heads anyways? Maybe followed up by some liquid glass in the cooling system and a quick push out the door?

-klb

[scott123]

Never thought about the liquid glass.

I will keep that in mind. LOL

S

[CaptRMW]

Het Grumpy I had a Jackleg that rode a jackass to work build my engine (GM engine plant south of the reeever) I am on my third one and hoping he got this one right. $5.00 per hour what do you expect.

[dan s]

Tough to tell from the pics, but it looks like dark areas on the head gasket fire rings and also some strange looking stains. Check insde edge of fire rings for cracks. Did you have the heads checked for cracks? If it was me I would put some new quality head gaskets on some new head bolts (sealer on bolts that go into the water jacket) torque it properly and run it. It would be nice to find some obvious damage to the head gaskets, but if not you have already got money into the cylinder heads so add new gaskets and go!

[HO455]

Sounds like it may have gotten real hot at some point.

[OBS454]

Originally Posted by dan s

Tough to tell from the pics, but it looks like dark areas on the head gasket fire rings and also some strange looking stains. Check insde edge of fire rings for cracks. Did you have the heads checked for cracks? If it was me I would put some new quality head gaskets on some new head bolts (sealer on bolts that go into the water jacket) torque it properly and run it. It would be nice to find some obvious damage to the head gaskets, but if not you have already got money into the cylinder heads so add new gaskets and go!

X2 Fel-Pro - Quality torque wrench - take your time

[BCOWANWHEELS]

I,ve got a lot of nice gm heads 4 sale, cleaned and maged