ok I pulled the heads off on both banks had the machinist re-check all his work and one of the heads the head that was part of the bad cylinder had a crack in it right in between the valves for that cylinder that had the piston replaced. after pulling the two valves out that where next to the crack you can see that the vavles where a blueish color from being exposed to to much heat. anyone have any ideas on why just one cylinder would over heat? My tempatuire gauge never went over 200 so the whole motor didnt over heat as a whole unit it was just that 1 cylinder that over heated

 

That much heat can only be causes by a lean fuel mixture but,,,,,, The head is NOT normally the failure point for too much heat. I have never seen a head crack for to much heat in a single cylinder. Heads crack because of the stress caused by the whole head growing. A single cylined should not cause that.

I have seen a lot of engines that have been trashed becuase one cylinder overheated. It will melt the electrod off the plug it will destory the rings. Even a slightly lean cylinder will cause pitting in the top of the piston long before it hurts anything else in the worst cases the center of the piston with break away. Even in the worst cases the coolant keeps the head from growing too much to crack.

The more likely cause is what ever damaged your piston caused a small surface crack in the head and under pressure it opened up. The reason it looks like heat damage is because the edges become what we call heat risers and can not bleed off the heat fast enough.

After you make the repair use one of those heat measuring guns to verify the exhause manifold tube not any hotter then the other cylinders. If it is hot swap an injector with another cylinder and see if the heat follow the injector.

 

And you're wondering how the head got cracked? For the bolt to have broken the piston, it would have whacked the head good and hard. Your machine shop didn't notice the crack when they did the valve work the first time. Given the circumstances, that head should have been gone over with a fine tooth comb.

 

Right on thanks for the info I know everyone recommends dropping new engine but I've already put to much into this engine just to stop working on it but I got a new head will be putting everything back together within next week or 2 hopefully

 

Ok sorry I haven't been on for awhile. I got my motor rebuilt for the second time again I did all the work myself. The car is running good, I put about 300 miles on it and then my front timing seal started leaking. I have pulled the crankshaft pulley off replaced the timing seal and it is still leaking and i'm talking a steady stream of oil and it will only start leaking after about 3 min of the engine running. Does anyone have any suggestions of what i could do to possibly fix the problem. I have read that on the V8's the frnt timing cover has to be aligned just right to form a perfect seal around the crankshaft pulley, but on my 3.8l there are alignment pins so I don't think there is much room for additional adjustemnts. I also put a drop of RTV on the key of the crankshaft.

 

You want to check the crank for wear makes. It is not uncommon for the front seat to wear grooves in the crank. The crank will need to be sleeved to repair this condition.

 

Are you reffering to the female end that comes out of the pulley that comes in contact with the seal, or are you talking about the male end of the crankshaft that the pulley bolts on to? The pulley has a small groove worn into it kind of where the seal wraps around it.

 

There's the source of your leak, the seal isn't sealing against that groove. Get yourself one of these: Harmonic Dampener (and I didn't say balancer) Repair Sleeve
You're supposed to use an installation tool, so ask if they have one in their tool loaner stash.

 

ok ill look into it. Any ideas on how to get the crankshaft bolt torqued back down and strectched to specs? The ways im familiar with are getting to the fly wheel and using one of the flexplate holding wrenchs or whatever it's called but i dont have one of them wrenchs.

 

Ok here is an update. I pulled the harmonic balancer back off found a groove worn into it so I sleeved the harmonic balancer put a new seal in tightened everything up. It is still dripping oil not nearly as bad as before i sleeved it. Now it is only dripping out at higher rpms. Seems like after the car warms up ill hold it at about 3000rpms for few seconds and the oil will start trickling out. I can not pinpoint the leak because i cant see directly behind the pulley but im thinking it could be the oil pan, but that gasket had been replaced during the rebuild. I'm at a dead end if anyone has any suggestions feel free to share.