3400 head gasket destruction

[AaronGTR]

Yeah, I definitely don't plan on using that cam anymore, and I wouldn't feel good selling it to anyone if there might be something wrong with it. I would be willing to do that.

I already decided to get a new cam from Ben anyway. The car hasn't really run "right" with this profile since day one anyway, and I want something more reliable with better driveability, but still a little more punch than stock. I just need to source a new stock oil pump gear now. Can't find them anywhere.

I found a local place I can rent an engine hoist by the day though, so I'm going to try and pull the engine next week and tear it down while I'm waiting for parts to get here.

[02GT_Skyhigh]

Best of luck with the tear down.
There is a lot of wrench time a head for you.
May Murphy's Law not affect this job. haha

[Azrael]

I wonder if there was a nick in the fire ring where it failed on the headgasket. It would have been a focus for stress and heat, both of which are aggravated by boost.

[kwhauck]

This makes me wary of the Billet Cam that I have.....seemed like a new bronze gear every winter.....

[MilzyZ34]

i did mean to say "stock" gear and not "bronze" gear on that first sentence.

when i posted, i also didn't realize the pictures you took were of the same oil pump drive shaft. that's weird how it's only worn on one side. i have a question though ... if the cam is the problem and is somehow not concentric and wearing unevenly on the oil pump drive, how is it that the wear is always in the same spot on the oil pump drive gear? the gear on the cam is larger than the other, so wouldn't it stand to reason the contact area on the oil pump gear would never be constant with the spot on the cam's gear where the supposed damage was. In other words, if the cam was truly the problem, wouldn't the oil pump drive show wear all around the gear since this contact area would always be changing due to the differences in diameter. In my opinion, if the wear is on the oil pump drive gear, and always in the same spot, this would seem more consistant with the oil pump drive being bent and rotating non-concentrically to it's designed axis.

just because you didn't see any knock on a scan doesn't mean the engine didn't go lean. a headgasket failure like that looks a lot like a problem with excessive cylinder pressures and heat. at the boost you're running, you shouldn't be bursting headgaskets like that, (assuming the gaskets were installed correctly), so it seems to me the problem is excessive pressure due to the increase in temperature in the cylinders from running lean. the air-fuel ratio in the dyno chart you posted very clearly hits 13.3:1 and change at the end. Ideal would be like 11.5, 2 points lean is a pretty big deal. do you have any scans from that run? what injectors are you running? gtp 36's? we upgrade those at around 265whp on a supercharged car because they're approaching dangerously high duty cycles, plus you've already admitted they are static with your setup from the scans you've seen. Is it really so much of a stretch that your engine failed due to running lean? I suppose your timing could also be too high, which would also cause the problem with excessive heat. scans would help diagnose this, also pictures of the plugs and combustion chambers.

[AaronGTR]

i did mean to say "stock" gear and not "bronze" gear on that first sentence.

when i posted, i also didn't realize the pictures you took were of the same oil pump drive shaft. that's weird how it's only worn on one side. i have a question though ... if the cam is the problem and is somehow not concentric and wearing unevenly on the oil pump drive, how is it that the wear is always in the same spot on the oil pump drive gear? the gear on the cam is larger than the other, so wouldn't it stand to reason the contact area on the oil pump gear would never be constant with the spot on the cam's gear where the supposed damage was. In other words, if the cam was truly the problem, wouldn't the oil pump drive show wear all around the gear since this contact area would always be changing due to the differences in diameter. In my opinion, if the wear is on the oil pump drive gear, and always in the same spot, this would seem more consistant with the oil pump drive being bent and rotating non-concentrically to it's designed axis.

I said it was the same gear in my post. And it's not worn on only one side. You can clearly see it's worn on both sides, and just more on one side than the other. It's also worn more than it was last time I checked it 6k miles ago. It's the same oil pump drive that's been in my car for 63k miles. It lasted 50k with the stock cam with no wear, and 12.5k miles with the billet cam and it's almost toast, so I don't see how it could be the drive gears fault. If it was bent/bending I would have had the same problem with the stock cam, and much earlier.

just because you didn't see any knock on a scan doesn't mean the engine didn't go lean. a headgasket failure like that looks a lot like a problem with excessive cylinder pressures and heat. at the boost you're running, you shouldn't be bursting headgaskets like that, (assuming the gaskets were installed correctly), so it seems to me the problem is excessive pressure due to the increase in temperature in the cylinders from running lean. the air-fuel ratio in the dyno chart you posted very clearly hits 13.3:1 and change at the end. Ideal would be like 11.5, 2 points lean is a pretty big deal. do you have any scans from that run? what injectors are you running? gtp 36's? we upgrade those at around 265whp on a supercharged car because they're approaching dangerously high duty cycles, plus you've already admitted they are static with your setup from the scans you've seen. Is it really so much of a stretch that your engine failed due to running lean? I suppose your timing could also be too high, which would also cause the problem with excessive heat. scans would help diagnose this, also pictures of the plugs and combustion chambers.

Again, your reading comprehension fails you.

I HAVE A WIDEBAND OXYGEN SENSOR INSTALLED IN MY CAR!!! I log all my runs with it, and it is installed at the end of the headers... so it's obviously going to be more accurate than a sensor the dyno shop put in the end of my tail pipe after the catalytic converter, which is what is on that dyno graph.

I never went higher than 12.6:1. Yes, the injectors are maxed and need to be upgraded. I already know that. If I had the money to do it before I went to the track I would have but I didn't. 12.6:1 is still a relatively safe AFR and I was getting minimal KR. 2 degrees or less in second gear and 4 tops in third gear on the first run. Second run showed none at all. Timing is 14-16 degrees in the top end, so it's not high. I pulled timing until it stopped having an effect on KR. Plugs and combustion chambers look fine, other than being wet with coolant. As I already said, I don't KNOW why the head gaskets failed. I never blamed it on the cam though. It may have been a contributing factor affecting other parts that led to the failure, but I doubt it was directly involved. All I said was that it was definitely wearing my oil pump drive gear, which is a perfectly reasonable assumption to make based on the evidence. I'm sticking with that until I see some evidence to the contrary. So stop trying to shift blame onto my car and my tuning for something I'm not even accusing you of.

[pocket-rocket]

Out of curiosity, what brand/type of head gaskets were those? I know 95-modified hasn't had that good of luck with Felpro and swears by stock OEM gaskets before the Cometics were available. I've never had trouble with Felpro, although I don't really do anything other than stock applications with them besides my car (which isn't much as far as performance goes, anyways).

[stewartfn18]

it was the updated 04+ gm graphite head gaskets. ive used felpro too eveytime i swapped my hg's, but using the 3500 top end so i lost a half a point of compression so i wouldnt have a problem

[90BlueZ]

12.6 is lean, let alone 13.3 :P You can say you were not running too lean but the head gaskets sure seems to prove the opposite I was exploding everything (pistons and felpro HG) until I made sure AFR was staying under 12, ideally around 11.5.

The MS3 AFR safety feature and J&S knockguard individual knock cylinder control sure helps too

[AaronGTR]

Well I got the engine out and disassembled this weekend. Found some curious things. The oil pump and the timing set still look fine. Little bit of slack in the chain but not terrible. The rotating assembly still turns over easily and there are no visible signs of damage on the pistons or rods. I did find one odd thing though. I rotated each piston to it's peak height and placed a machinists ruler across the top to check the gap to the deck with a set of feeler gauges. Most of the pistons had more gap on the top (by the lifter) than the bottom, except for #1 which had a bigger gap on the bottom side. They all had about .023" of a gap except for #2 which only made it up to the deck height but never went above. It was the only one to do this and that is the only cylinder that had carbon build up on the piston and head. Do you guys think maybe the rod or the pin or bearing may be damaged somehow and that cylinder has been running with lower compression?

I took the cam out and it looked fine. No wear on the lobes or the gear. There was what looked like it might be some wear patterns on the journals, but they still felt smooth. I'm not sure about the cam bearings though. I think they might need to be replaced. The front one looked like it was only worn on the bottom part and the rest was kind of rough, but there where three little orange/copper spots showing.



This was one of the middle ones. More uniform all around, but a lot more orange showing.



The other middle one.



There was an odd wear mark on the thrust plate too. Kind of off center and more worn on one side and almost not touching on the other. Any thoughts on that?




I was already planning on taking the heads to a shop to check the valve guides and make sure the heads are flat, and deck them if needed. I'm starting to think I'm going to have to take the block in too and get the cam bearings changed and have them check the rod bearings and the rest of the rotating assembly.

[SappySE107]

You have a piston that doesn't stick .020 out of hole? That is a problem. I am interested on what the problem/difference is with that piston, rod, or crank throw.

[trotterlg]

I have seen the rough type finish on the cam bearings that are the type that are formed with a rolled piece of steel. It looks like they put a rough finish on them and let the cam wear it down. Check to see if you can see a seam on the bearings, if the are not the full circle type with no seam then I think what you see is normal, it may not be good but it is how they act. Larry

[AaronGTR]

Yeah, I looked for that on the outside bearing. No seam that I could see. Looks like one piece.

[AaronGTR]

ok well, my plans have changed rather drastically now. I'm going to return all the valve train to stock for now. The billet cam was designed with the newest style timing ring (03+ I think it was?) and I switched to the newer cam sensor when I installed it. I seem to recall someone later saying that they all worked the same and any of the sensors would work with any cam. Is that correct? Just wondering if I can put my stock cam back in without changing the sensor back 'cause I'm not sure if I still have the old one.

[pocket-rocket]

ok well, my plans have changed rather drastically now. I'm going to return all the valve train to stock for now. The billet cam was designed with the newest style timing ring (03+ I think it was?) and I switched to the newer cam sensor when I installed it. I seem to recall someone later saying that they all worked the same and any of the sensors would work with any cam. Is that correct? Just wondering if I can put my stock cam back in without changing the sensor back 'cause I'm not sure if I still have the old one.

That is correct. I redid a 3400 in a minivan (98 or 99 TranSport) and used a 3500 cam without changing the sensor and the PCM never made a complaint.