head gaskets: take two

[AaronGTR]

Thought I'd give an update, in case anyone is interested or wants the info.

Worked on the car for three days over labor day weekend. First thing I did was drop the oil pan and get the oil pump cover off. I de-shimmed the pressure spring and put it back in. The oil pressure is still higher than I ever saw with the stock pump, but it's better. Stock pump was usually 18 psi at warm idle and never got over 50 psi. This melling pump is 25 psi at warm idle and sits around 50 psi at cruising rpm. When cold or at higher rpm it doesn't get up over 75 psi anymore though which it was doing before, so that is good. Seems the pressure bypass spring in the melling is definitely stiffer than OEM, but it's opening earlier now without the shims.

I also took the top end apart, took the heads off and changed the gaskets. The MLS gaskets had oil all over both sides of them and the outer layers where unstuck from the middle layer. The front gasket was loose and the head lifted right off without sticking at all, and the rear gasket was stuck to the head but not the block. Here's what the combustion chambers looked like.





Basically a lot of carbon build up. Too much for only 1k miles. I burned through 1qt of oil in that time, and about the same amount of coolant. The oil on the combustion chambers is just from pulling the heads off and tipping them over. It ran off the gasket area. Most of the rubber coating is gone from the gaskets.



Top of the pistons where covered in carbon build up, and there was a black ring around the top of the cylinder walls. Some cylinders it went all the way around, some the ring stopped in between cylinder pairs by the coolant ports, which I think is a good indication it was leaking coolant there.

[AaronGTR]

All the exhaust runners had a lot of really black carbon in them, but the worst was the #2 runner. Really heavy build up in spots, but also wet oil in it with a trail coming from the valve guide. The header primary was also full of heavy build up and wet oil.





Pulled the valve spring off and found this. The spring shim was all chewed up and had worn a groove in the outside of the valve guide. Weird thing is the valve seal was still pretty tight on the guide, but the valve seemed a little loose to me in the guide. I don't have a dial gauge to check the run out though so I'm having the shop check it.





So basically there was no way I was putting those heads back on the engine. Luckily I still had a set of stock heads already assembled in a box back at my apartment. I cleaned them up a little and put those on with Felpro SD head gaskets and new LIM gaskets. Everything seems to be running better and no signs of burning any fluids at this point.

[AaronGTR]

I took the heads to the machine shop yesterday for them to look at. They said they had never seen a spring shim get chewed up like that before and don't know what would have caused it. As for the oil getting in the combustion chambers, since I was only getting smoke occasionally at idle and not while driving or any big puff of smoke when I hit the throttle, they said that was an indication that it was only pulling oil in from somewhere under high vacuum which means it's probably NOT the piston rings. It's more likely from LIM gaskets, valve seals, or head gaskets.

They did say they've seen a lot of sealing problems with MLS gaskets, especially on Nissans. If they aren't perfectly flat and smooth they won't seal up properly, and they agreed that sometimes they do need copper gasket spray, even though Cometic says they don't. Some head milling machines simply aren't capable of producing a smooth enough surface, and the spray is needed to fill in the tiny imperfections and create a tight seal. They also said the factory head finish is typically the best, and they don't like to mill the heads unless the surface flatness is off by .003" or more. If it's .002" or less they usually don't touch it, and they didn't mill mine so he said they should be flat.

However they did recommend that I not use the MLS gaskets and use a stock type gasket. They said at my power level a MLS gasket shouldn't be needed, and that good tuning and the head studs should be enough to keep them from blowing. One theory they had was that the combination of the head studs and MLS gaskets could have contributed to the leak, because those parts from different manufacturers aren't designed to work together. The OEM style gaskets are more compressible and allow the heads to expand downward slightly with thermal expansion, where the MLS gaskets are harder steel and will expand themselves when heated. They also asked the torque specs for stock head bolts and the ARP studs, and said the studs should only be clamping around 15-20 ft/lbs more than the bolts, but that they don't stretch as much as the bolts do. It's possible that the combination of the MLS gaskets and the stronger head studs where not allowing the heads to expand and contract as they normally would and could have caused distortion making the gaskets not seal as they normally would.

Normally when you take the LIM off you can also see a line around the ports where the gasket touches. On my ported LIM the line for the gasket looked good around three sides but on the top of the ports it looked like the gasket was right at the inside edge of the port. Perhaps with the thermal distortion it could have caused the head or LIM to lift up or pull apart somehow and reduce the sealing pressure there letting oil mist from the lifter galley get pulled in when the vacuum was high enough? It would sort of make sense with what I saw. There was a light oil residue in all the intake ports that didn't look like oil leaking from the valve guides because it went up past the valve guides into the LIM runners. I thought this was just residue from the PCV system, but maybe it was from the gasket leaking?

Anyway, for now I have stock heads back on with the felpro head and LIM gaskets. The machine shop has my other heads and they are going to recheck them for flatness then check all the valve guides and the rest again. They said they will let me know what they find, and they will replace the #2 exhaust valve guide and give me a new spring shim. If any of the other valve guides are bad then we might replace them all, but they would have to re-do the valve job then. So we'll see what happens. For now my supercharger got here today so I need to go reinstall that, and I have parts on the way for the headers. I decided I was tired of the crossover pipe not lining up right, so while I still have my welder I am cutting off the flared ends and replaced them with v-band flanges.

[bszopi]

One theory they had was that the combination of the head studs and MLS gaskets could have contributed to the leak, because those parts from different manufacturers aren't designed to work together.

This theory boggles my mind... Cometic doesn't make studs but are a very popular MLS gasket. ARP doesn't make gaskets, but are probably the #1 fastener company in the world. According to their theory, no one would ever run these 2 components together because they are from different manufacturers. Yet, I can almost guarantee they do, and a lot of people.

[bob442]

i would blame the valve seals.

[ForcedFirebird]

What kind of machine shop are you going to? First they tell you to run heads that had blown gaskets without milling, now they tell you you can't run ARP and MLS? They tell you NOT to tq the head studs to ARP's spec?

Milling machines are more than capable of a 50ra, they have to speed up the spindle and slow the feed rate on a final pass set to .0005-.001". If they can't their cutter is in poor shape, but something tells me this "machine shop" probably doesn't even own (or maybe know how to use) a profilometer. Then they tell you if the head is less than .003" out, they would run a metal gasket on an iron block with it? Are you serious?

ARP and Cometic (or any other MLS) have been used in combination by hundreds of thousands or racers for years without issues, that's common knowledge.

I see you on a lot of forums boasting how much you know, but how much experience do you really have using high performance/aftermarket parts? Not trying to attack you personally, but when myself and others have had many, many successful engines with these combinations, it's the MFGR's fault that your car leaked? Just putting one and one together here.

[1988GTU]

Anyway, for now I have stock heads back on with the felpro head and LIM gaskets.

What did you do to the heads prior to installation?

[ForcedFirebird]

What did you do to the heads prior to installation?

This is take two because the heads/MLS were put back on the motor, untouched, after a head gasket failure.

[AaronGTR]

i would blame the valve seals.

I was kind of wondering about that too since they didn't use the same seals I had on there before. Of course, I was using the orange and green 3.1L seals too and not the stock 3400 seals. I could possibly go back to running 3400 seals but I'd have to switch to comp springs since the Ls6 springs won't clear those one piece shim/seals. Also the spring pocket on those heads where machined down .1" so I don't know if they'd still fit all the way over the valve guides or not.

What kind of machine shop are you going to? First they tell you to run heads that had blown gaskets without milling, now they tell you you can't run ARP and MLS? They tell you NOT to tq the head studs to ARP's spec?

Milling machines are more than capable of a 50ra, they have to speed up the spindle and slow the feed rate on a final pass set to .0005-.001". If they can't their cutter is in poor shape, but something tells me this "machine shop" probably doesn't even own (or maybe know how to use) a profilometer. Then they tell you if the head is less than .003" out, they would run a metal gasket on an iron block with it? Are you serious?

ARP and Cometic (or any other MLS) have been used in combination by hundreds of thousands or racers for years without issues, that's common knowledge.

I see you on a lot of forums boasting how much you know, but how much experience do you really have using high performance/aftermarket parts? Not trying to attack you personally, but when myself and others have had many, many successful engines with these combinations, it's the MFGR's fault that your car leaked? Just putting one and one together here.

Not trying to attack me personally?... but you and Ben ARE attacking me personally when all I am trying to do is provide more information to the community. I see you on a lot of forums boasting how much you know, but so far you haven't proven anything to me except that you can't read. I said they told me they don't normally deck the heads if they are within .002" not .003". Maybe the shop manager didn't tell them I was using MLS gaskets, I don't know. If I had specifically requested that the heads be decked, that would be a different story. If that wasn't sufficient enough and the heads REALLY needed to be decked, again..... maybe you guys could have put something about that on your store front?! Or returned your phone calls? I dunno, kinda makes sense to me. And where did you read that they told me not to torque the head studs to ARPs specs? I NEVER said that! Anyway they said they've seen other people have problems with MLS gaskets sealing even with perfectly flat heads, and that seems to be what I've seen from searching other forums too. They've had better luck with the SCE copper gaskets, which again matches what I've heard elsewhere, but they are more expensive and they don't make them for the 3400. Still doesn't change the fact that the MLS gaskets didn't work on my engine, or that I don't really need them anyway.

This is take two because the heads/MLS were put back on the motor, untouched, after a head gasket failure.

Wrong. The MLS gaskets where NEVER installed on the car before, and they are not on now (nor will they be again). They were brand new, and where never removed and then reinstalled. The heads where checked out and deemed to be ok. They where completely gone over and said they were flat enough. I had them put in 3500 valves and do a valve job, and machine the spring seats .1", then they reassembled everything using my original springs/shims/retainers and new valve seals. Now if we're done with the bullshit, can we actually have a logical discussion here?


I found another problem today that hopefully might explain some of it. There was a lot of oil puddled in my upper intake behind the throttle plate, the oil level in my catch can went up 3/8", and my oil level was down 1/4 of a quart. I had just checked the level the day before so this happened in one day of driving. I'm not sure what caused it, but apparently my PCV line was sucking large amounts of oil out of the valve cover. It's possible a lot of my oil consumption was coming from there, along with the bad exhaust valve guide of course. Maybe the oil was actually getting sucked in the combustion chambers through the intake ports and some of it pushed into the gasket under compression and that's why they were all oily. Doesn't change the fact that the gaskets still didn't seal properly, but it makes more sense as to where the oil came from. I'm currently trying to figure out why so much oil got to the line in the first place and how to stop it.

[1988GTU]

This is take two because the heads/MLS were put back on the motor, untouched, after a head gasket failure.

What i was asking was what were done to the stock heads during this last install. Like were the heads resurfaced or left untouched? You read past what i was asking FF.

[AaronGTR]

yeah,nothing was done to the stock heads. They never had any problems. They only had about 30k miles on them when I took them off and they haven't been used since. I just cleaned up the sealing surfaces and took the valves out and oiled the stems a little since the guides were pretty dry just to pre-lube them, then put back together and installed on the block with felpro SD gaskets.

I didn't really have the option to do anything to them anyway even if I wanted to. I hadn't planned on putting them back on in the first place... I was originally just changing the head gaskets and going to re-use the other heads until I found the bad exhaust valve guide. I was staying at my friends house while I was working on the car for 3 days, and I had to borrow his car to go get the stock heads from my apartment. The machine shop obviously wasn't open, and I had to get the engine back together and running so I could get to work Tuesday.

[SappySE107]

They also asked the torque specs for stock head bolts and the ARP studs, and said the studs should only be clamping around 15-20 ft/lbs more than the bolts, but that they don't stretch as much as the bolts do. It's possible that the combination of the MLS gaskets and the stronger head studs where not allowing the heads to expand and contract as they normally would and could have caused distortion making the gaskets not seal as they normally would.

but so far you haven't proven anything to me except that you can't read.

And where did you read that they told me not to torque the head studs to ARPs specs? I NEVER said that!

Looks pretty close to them saying to use 15-20 ft lbs more than stock.

I don't see your gaskets listed on the store so I can't update it.

Sorry I moved earlier this year and didn't answer my phone when you needed me most. Its obvious that was the reason you have had all these engine problems.

[1988GTU]

yeah,nothing was done to the stock heads. They never had any problems. They only had about 30k miles on them when I took them off and they haven't been used since. I just cleaned up the sealing surfaces and took the valves out and oiled the stems a little since the guides were pretty dry just to pre-lube them, then put back together and installed on the block with felpro SD gaskets.

I didn't really have the option to do anything to them anyway even if I wanted to. I hadn't planned on putting them back on in the first place... I was originally just changing the head gaskets and going to re-use the other heads until I found the bad exhaust valve guide. I was staying at my friends house while I was working on the car for 3 days, and I had to borrow his car to go get the stock heads from my apartment. The machine shop obviously wasn't open, and I had to get the engine back together and running so I could get to work Tuesday.

So you did not have the stock heads that you JUST put on resurfaced at all recently? Correct?

[AaronGTR]

So you did not have the stock heads that you JUST put on resurfaced at all recently? Correct?

No, the stock heads that I just put on have never been resurfaced. They are the factory finish, just as they were when I took them off my engine years ago. All I did was clean them up and oil the valves. I had not planned on using them again any time soon, and I ended up needing them right away, so I didn't have time to do anything to them. They shouldn't need to be resurfaced though. They never had a head gasket issue while they were on the car, and I used them with OEM style gaskets.



And now for what I did today. Went and bought a new compression tester just for the hell of it and did a compression test. Pressure was between 175-180psi on every cylinder and pressure built up exactly as it was supposed to as described in the manual. So much for the "your rings are bad" theory.

I made some changes to the PCV system to make it more like the final system will be once the SC is back in. I had taken out the PCV valve and done a temporary hook up when I did the top end work two weeks ago, because I can't finish everything until the SC is back in and I know how it will fit. I'm re-routing the system to the intake manifold like stock instead of through the SC because I don't want the oil residue getting in there, and I'm putting a check valve in the line for when it's under boost. In the reading I did last night I found the PCV isn't just a check valve but also meters the flow volume depending on the vacuum applied to it and the pressure in the crank case, so I guess it has to stay in the system. That might explain the large amount of oil coming through the line at least for the last two weeks, but the PCV was still in before the last tear down and head gasket change, so that doesn't completely explain the oil consumption. It might still be slowly sucking too much oil even with the valve in place. Not sure yet.

I took another stainless scrub pad like I used in my customized catch can and I sandwiched it between the splash shield and valve cover on the inside of the valve cover. Hopefully that will act as sort of a pre-filter and help block any heavy oil splash from getting behind the shield and sucked up the line. Then I sanded down the threads on the brass fitting I had JB welded in the valve cover port, just enough so the old PCV valve would slide in. Didn't take much. I put some RTV around the outside of the valve and pushed it in, so that should keep it from leaking at all. The old rubber grommet used to leak and get oil all ove the valve cover. The OEM line size is 3/8" so I changed out all the NPT/hose barb fittings I was using for 3/8" and changed all the hose over to 3/8" instead of the 1/2" I was using. Hopefully that will keep the flow volume and speed correct. Last thing I did was put my check valve on the outlet side of the catch can, since that is the side it will be on anyway when the SC is on.

I also ordered another catch can from elite engineering. It's designed for LS engines, but catch cans are pretty universal and it has the correct 3/8" fittings I need. All I have to do is make my own bracket instead of using the one they provide. Then I'll have a dual can system. Ships tomorrow so it should be here next week. Once I install that then I can drive it a while and keep an eye on the oil levels in the pan and the catch cans, and take the intake tube off ocassionally to check for oil and see if that solves it.

[bob442]

i'm just going to throw this out there, that it could be possible that you originally blew your head gasket due to hydro locking with oil from worn valve guides/seals. Regardless of what gaskets you put on the motor the second time, you would have had a similar problem as the oil leaking down the block or blowing out another gasket. now that you have changed the heads, this problem will disapear. End result the gaskets are probably toast now, and heads are a waste of money to fix.

I am no Master Motor Builder, or have a degree in Failure Analysis Engineering, but i could make this assumtion from the pictures i veiwed on that pontiac forum. How ever i cant figure out how you got your surface of the failer heads to be so clean, it almost looked like they were infact machined, but i could tell from the resolution.

I hope we can all come to a conclusion together civily and put this behind us.