Heads pulled
Thread Starter
Drifting
Joined: Jul 2005
Posts: 1,375
Likes: 2
From: Austin Texas
Heads pulled
So when I broke a valve spring a week ago, I decided to increase my LS6 education and pull the heads myself. It's been a good task so far; got them out last night and to the machine shop this morning.
The inside of the cylinders look very black and there's a good amount of flakes of black stuff too. Looks like it's not burning clean, but I have nothing to compare it to, as I've not pulled heads before on this motor.
Question: What should the inside of the cylinders look like? How clean?
Lastly, what should I do to clean the piston tops while the heads are off? Thanks.
The inside of the cylinders look very black and there's a good amount of flakes of black stuff too. Looks like it's not burning clean, but I have nothing to compare it to, as I've not pulled heads before on this motor.
Question: What should the inside of the cylinders look like? How clean?
Lastly, what should I do to clean the piston tops while the heads are off? Thanks.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Start with the softest cleaning methods first. I would use some SEA FOAM spray (Creep) and a GREENE SCRUBBING PAD to remove The carbon. If there are any tough spots, use a small tooth brush type brass wire brush.
Then some carb cleaner to flush out all the junk.
MAKE SURE THAT YOU ABSOLUTELY CLEAN OUT ALL THE HEAD BOLT HOLES!!!!!!! There can NOT be any moisture/water in the bolt holes when you reinstall the head bolts!!! I use a compressor with an air nozzle attachment with a long metal tube to blow out the holes until they are DRY! If there is any water in the holes, you could crack the block! Look in the hole with a light and if you cant see the bottom of the bolt holes, keep cleaning.
BC
Then some carb cleaner to flush out all the junk.
MAKE SURE THAT YOU ABSOLUTELY CLEAN OUT ALL THE HEAD BOLT HOLES!!!!!!! There can NOT be any moisture/water in the bolt holes when you reinstall the head bolts!!! I use a compressor with an air nozzle attachment with a long metal tube to blow out the holes until they are DRY! If there is any water in the holes, you could crack the block! Look in the hole with a light and if you cant see the bottom of the bolt holes, keep cleaning.
BC
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
I agree completely. I used a vacuum modified to hold onto a piece of copper tubing to get the coolant out of there.
Black flakes in the cylinders is a bit worriesome. No idea where it came from? Was there black carbon on the tops of the pistons? I'm sure there will be some, but how much? On the cylinder side of the heads, any significant carbon there...flaky stuff that would have fallen off? What about the intake manifold...looking for garbage in there?
The inside of the cylinders should be prefectly smooth. No scars, no abnormal marks or discolorations and certainly nothing raised on them. Was there any marks or obvious damage to the top of the piston of the cylinder with the broken spring?
Black flakes in the cylinders is a bit worriesome. No idea where it came from? Was there black carbon on the tops of the pistons? I'm sure there will be some, but how much? On the cylinder side of the heads, any significant carbon there...flaky stuff that would have fallen off? What about the intake manifold...looking for garbage in there?
The inside of the cylinders should be prefectly smooth. No scars, no abnormal marks or discolorations and certainly nothing raised on them. Was there any marks or obvious damage to the top of the piston of the cylinder with the broken spring?
Thread Starter
Drifting
Joined: Jul 2005
Posts: 1,375
Likes: 2
From: Austin Texas
The inside of the combustion chambers is pretty black. The flakes appear to be on the piston tops, could have flaked off from the top of the cylinders. The walls are smooth and clean; no issues there. I'm mostly worried the engine is running rich, or that I need a catch can to pick up excess oil blowing into the intake.
The top of the piston that took the valve hit has a faint eyebrow on it; no deformation compared to the others, that I can see or measure. Going to start cleaning the block tomorrow! Very excited to be turning the corner and getting it back together.
The top of the piston that took the valve hit has a faint eyebrow on it; no deformation compared to the others, that I can see or measure. Going to start cleaning the block tomorrow! Very excited to be turning the corner and getting it back together.
Tech Contributor
Joined: Dec 2006
Posts: 10,962
Likes: 29
From: Van Buren Arkansas
Wounded Warrior Escort '11
The one that took the hit might need replacing which is a more involved job by far. I don't think there is an allowance for this but a more formal engine guru can better advise. I would look at it as a possible weak spot which could spell disaster if it lets go. I've never seen one of these pistons out so I really don't have a clue if you have an issue or not. Clean everything off carefully. I used razor blades and took my time doing so. I also lightly pre-lubed the walls just before reinstalling the heads to insure they weren't dry for the first start. Make absolutely sure those block to head surfaces are totally clean and like others have already said, be sure that the bolt holes are empty of any debris and fluids. Take your time to do it right. ps..I had my heads off to change the lifters.
Team Owner
Joined: Mar 1999
Posts: 22,025
Likes: 192
From: At the beach in little Rhody
I actually use a bamboo chopstick ground to look like a chisel to get the carbon off. Works well and won't scratch the aluminum. The carbon usually comes off in small chunks and then you can clean the piston top afterwards.
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Thread Starter
Drifting
Joined: Jul 2005
Posts: 1,375
Likes: 2
From: Austin Texas
Symptoms:
Driving the car at 65 mph on the freeway. Slowing for an exit ramp. When I came off the gas, the check gauges lite came on, and the engine stumbled. I knew something was very wrong so I shut down and coasted to a stop, then pushed the car to the side of the road.
When we got it to the shop, the mechanic attempted to start the car (!) and it sounded very, very bad. It did start up. We shut down after 10 seconds or so. No codes whatsoever, save a broken wheel sensor where the tow truck guy had hooked on wrong (free tow from that; had to replace the sensor).
Compression test showed wildly variable results, including one zero reading, on cylinder #5. Other low spots were #8 at 75 psi and another at just 105. Pulled valve covers, and saw the broken spring. At that point, I decided to pull the heads.
When I got into the motor, I found just a small "eyebrow" mark on the #5 piston, no deformation (I've rotated the engine so that that piston is at the top). One bent pushrod on that cylinder. And the broken spring, of course.
Driving the car at 65 mph on the freeway. Slowing for an exit ramp. When I came off the gas, the check gauges lite came on, and the engine stumbled. I knew something was very wrong so I shut down and coasted to a stop, then pushed the car to the side of the road.
When we got it to the shop, the mechanic attempted to start the car (!) and it sounded very, very bad. It did start up. We shut down after 10 seconds or so. No codes whatsoever, save a broken wheel sensor where the tow truck guy had hooked on wrong (free tow from that; had to replace the sensor).
Compression test showed wildly variable results, including one zero reading, on cylinder #5. Other low spots were #8 at 75 psi and another at just 105. Pulled valve covers, and saw the broken spring. At that point, I decided to pull the heads.
When I got into the motor, I found just a small "eyebrow" mark on the #5 piston, no deformation (I've rotated the engine so that that piston is at the top). One bent pushrod on that cylinder. And the broken spring, of course.
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
If it was an intake valve that was the culprit, that allowed exhaust gasses to enter the intake manifold which caused the cylinders to all run very badly. That could account for the excessively rich looking cylinders. Once you get it all back together again and running, check the plugs andsee how they look!
When ENGLANDGREEN bent one of his valves, he had the same carboned up cylinders. They cleaned up fine and the engine ran great afterwards.
BC
When ENGLANDGREEN bent one of his valves, he had the same carboned up cylinders. They cleaned up fine
and the engine ran great afterwards.BC
Thread Starter
Drifting
Joined: Jul 2005
Posts: 1,375
Likes: 2
From: Austin Texas
So on a compression test, what values should I be seeing? Once I get it buttoned back up, I want to test again. Should I be looking at 150 all round? 180? Just consistent numbers? It's an unmodded engine; I don't even have an aftermarket intake on it.