NightmareTA

iTrader: (20)

Recently gave my turbo 5.3 a few good rips and on the last pull, it felt like it was hesitating. Pulled into a gas station and saw a bit of compression blowing out of my oil cap breather, and the antifreeze was bubbling in my overflow container. Temp gauge showed 210* and oil press was normal the whole time. Did a compression check and all cylinders were between 135 and 145 PSI except 3 and 5 which were both 60 psi. I am hoping and praying it's just a head gasket but I have a feeling I lost a ringland...hope for the best, expect the worst is what they say. My oil was clean and my antifreeze looks clean as well. Gave the car another rip on the way home after this happened and it felt strong, but there is still noticeable compression coming out of the breather. Thoughts or opinions?

Heres a few shots of the plugs. Never seen the yellowish/green tint before, but I have heard thats normal from the cleaning agents in gasoline.

Cylinders 1, 3, 5, 7





cylinders 2, 4, 6, 8





Ignore the black soot on the ceramic outer part of the plugs. I had a pass side exhaust leak from the manifold.

NightmareTA

iTrader: (20)

Bump...anybody?

TX RED

iTrader: (19)

are you running e85

rotary1307cc

iTrader: (5)

Id say you lifted between 3 and 5 and the outer water jacket, chance pistons are alright going by the plugs are still intact

Before you pull the head i would do a leakdown to verify you have low compression because you are leaking from cylinder to cylinder

rotary1307cc

iTrader: (5)

Didnt see the blowby originally... sorry atleast one ring pack isnt intac

NightmareTA

iTrader: (20)

Nope, straight 93 pump

So basically if it was just the head gasket that blew, there would be no blowby through the breather? I pulled the head and the pistons are all perfect from the top, but I know the damage can be underneath as well. I just want to be sure that if I pull the motor, it actually is bad rather than do all the work and find out it's fine.

denmah

iTrader: (2)

looks like alot of noise and spots from pinging on those plugs

smoke out the breather and 60psi means pooched

how much boost and timing on what gas?

denmah

iTrader: (2)

also when i knock a cyl it usually idles like **** all stumbly like its missing a bit

rotary1307cc

iTrader: (5)

you could leak into the lifter area and pressurize the case

usually will lift outboard though


should easily be able to tell from the gasket and deck surfaces to see where it was leaking

67Firebird455

iTrader: (27)

Definitely look at the gaskets and deck since you've got the heads off. I agree with these guys.

NightmareTA

iTrader: (20)

93 pump gas, 11 PSI through a T-netics 76mm, and I believe 22-23* timing.

The car idled and ran perfect after I noticed the compression coming out the breather. Even drove it about 25 miles home at 80 mph on the highway and honestly felt like it drove perfect.

The head surface and head gaskets both looked fine. Not really sure if I'm missing something, but nothing looked out of place...no cracks, melted areas, etc on either. I did notice what looked like a very fine scuff on the cylinder wall of #3, but you can BARELY catch a finger nail on it.

Ryans99ls1

iTrader: (16)

what headgaskets? i lifted the drivers head on mine and the stock gaskets looked like **** when i took them off, im surprised the motor didnt blow. If you dont see anything abnormal when the heads come off, put ls9s in and have at it.

a4ls2goat

Was it smoking ??

itsslow98

iTrader: (18)

That is a ton of timing for pump gas. Thats race gas type timing. Im thinking you got lucky and its a head gasket but that timing needs to come back down.

NightmareTA

iTrader: (20)

I don't see anything abnormal but there has to be a reason that the two cylinders both had only 60 psi in the compression test. Will probably be going with LS9 gaskets next time.

Nope, no smoke at all out the tail pipe

I wish I was certain about the head gasket though. I would hate to put it back together and find out it was the ring lands. It's weird that two cylinders next to each other would both blow a ring lands at the same time though.

I'm posting a few pics of the cylinder wall and head gasket. Maybe some of you will see something that I'm not.

NightmareTA

iTrader: (20)

Heres the mark on the wall of cylinder 3


Heres cylinders 3 and 5 and the area between them


Close up. You can see it looks like the intake valves were slightly touching the pistons as well. Odd since they are 317 heads and a stock LS6 cam??


One side of head gasket between 3 and 5


Other side of gasket between 3 and 5

TX RED

iTrader: (19)

That's a ton of timing...most people run 14-16 max

jay7199

iTrader: (9)

ring land... I just bought a 5.3 that was boosted, he drove on the car for awhile and it felt fine.. took it too the dyno, graph was out of wack.. did a compression test, #7 had 60PSI.. drove home just fine, i took it apart and sure enough.. ring land.

Lotta timing for pump gas! sucks, i know you just got this car on the road.

NightmareTA

iTrader: (20)

Yea it does suck donkey ***** man. This is the last thing I wanted to do after just getting to feel the power. Not gonna let it get me too down though. Just have to make it better now. Really considering going with H beam rods and wiseco forged pistons and pushing this 5.3 to 700+ rwhp reliably. We'll see.

lavoy

iTrader: (2)

drop the pan pull those two pistons drop in two used/new ones and lower the timing to 16 at that boost and have at it again. im sure you will find cracked ring lands down low probably from butting the rings, i like to gap the top ring a little on these junk yard motors.