head gaskets: take two

[AaronGTR]

On another note, I think I have an idea of why the original set of head gaskets might have blown.

I've been doing some more street tuning since getting the blower back on the car. Even though I'm using a bigger pulley and running less boost than before (2.5" vs 2.2") I'm actually getting detonation showing on the knock sensor much earlier now than before. The total amount of KR is no more than before, about 2-3 degrees tops, but it start almost as soon as I enter boost and before it didn't start until around 5psi+. My only guess is that since the old engine was worn and had more piston to wall clearance that the rings were also worn and allowing more blow by and that peak cylinder pressures were lower. If they are higher now that could contribute to the KR. Anyway...

While trying to log some WOT pulls to adjust the timing, I noticed it wasn't shifting like it should. It seemed like the trans was slipping or waiting to shift into the next gear and the engine was bouncing off the rev limiter 2-3 times. I don't really do any WOT shifting on the street like I would do at the track (it's not very safe) so I hadn't had a chance to figure this problem out, and it blew on the second run at the track before I had a chance.

I was using an excel sheet from the original DHP tuning forum to figure out my shift points. It was originally made for grand prixs, but you could put in whatever tire sizes and gear ratios you wanted and it would figure out RPM vs MPH, which is what you need to plug into the WOT shift tables. Well apparently something in the formulas still isn't right for grand ams. It was telling me I would shift from 2nd to 3rd at 84pmh at 6000rpm. Well on my scans I was seeing 6000rpm at 78mph. Went back and looked at my scans from the track and it did the same thing. Rev limit was set at 6300, but it would bounce off the limiter until the cars acceleration momentum carried it to 84mph and then grab the next gear, and it hit 6500 rpm at one point.

It blew right when it shifted into 3rd so I can only assume that the combination of maxed out injectors and the high rpm along with fuel cut from the rev limiter caused a sudden massive detonation. If it was bad enough and sudden enough it might not have shown on the knock sensor (I didn't see any KR at that point in the scan). I also have been having a problem with the analog input on the scanner that reads the wideband freezing up and not refreshing the data. This happened at the track too, so unfortunately I have no actual data about detonation or the AFR when it happened. That's the best explanation I can come up with though.

For now I changed the shift tables and set my 2-3 WOT shift to 78mph and now it shifts into gear crisply and right away. Now if I can get rid of the KR so it's not pounding my pistons/rods/bearings all the time I'll be all set.

[AaronGTR]

Time for an update. I got the heads back a couple weeks ago but hadn't had time to take anything off them and double check them. When I picked them up the guy who worked on them told me he cleaned them and remeasured everything and nothing had changed. He said the deck surface measurements were the same, and the run out on all the valve guides was within specs. He went ahead and decked them .002" to make sure they were perfectly flat, touched up the valve job to make sure they were perfect, replaced the one bad spring shim, put all new valve seals on, and reassembled them.

When I found the problem and took them in, I had told him about using the LS1 shims and 3.1 seals with the LS springs and that the shims didn't fit my stock valve guide diameter without drilling them out. He said he used a later model LS spring and it dropped right on. Well duh.... he didn't replace the valve guide and the outside is smaller than it used to be. This made me suspicious so I pulled off several of the other springs on both heads as well to check them out. Every single valve guide is like that. Here's a little better picture.



The shims used to be a fairly close fit, but now they are all loose. He said the bottom of the springs shouldn't move around that much... but I'm not so sure. Maybe it was enough to let that one get worn down? That doesn't explain why none of the others did that, or why that valve guide was leaking oil and none of the others were. There is still about 1/8" between the shim and the bottom of the seal and the spring would keep the shim pressed against the head so it wouldn't touch the seal. And all the seals seem pretty tight on the guides and around the valve stems, so I don't know why they would leak.

Since every guide is like that and they are far too smooth and uniform for it to be some kind of wear, I can only assume it's something the shop did, but why? I don't know if it was required for the tool they used to machine down the spring pocket, if it was accidental. Or maybe they just did it to fit the seals they were going to use? But if that was the case, why wouldn't they have called me and asked what seals I was using instead of just machining the guides and changing seals without notifying me? Anyway, for now I'm still not going to use these heads. The ones on the car don't seem to have any issues and I care more about reliability at this point than outright power. I might use them again in the future if I get a different cam again and have another car to drive. I might try getting a new set of LS1 shims and seeing if they fit tight without drilling them out now... or I might see if the stock one piece shims/seals will fit over them and stay tight and swap out the LS6 springs for Comp ones. That will be in the future though.

[SappySE107]

Torque to yield bolts are used because they are much more forgiving to the installation process that the factory uses. If you want the best, you have to do it precise, and that takes valuable resources like time and money. GM does not favor towards endless power capability and longevity over initial costs vs desired warranty periods. It is very easy for a stock GM motor to run torque to yield and MLS gaskets. MLS won't save your motor from poor tuning and detonation either, nor will studs.

[Fieroghini]

I just did the gaskets on my 3900 and GM had a very generous layer of a blue colored sealant around every hole and between every layer.

[AaronGTR]

Now that is some interesting info. Thank you!

I had read in that article that more cars where starting to come with MLS type gaskets from the factory now, and was wondering what they do to make them work. I figure since they have to meet warranty requirements and spend millions on engine research and development, that whatever they are doing is probably going to give the best results.

GM uses torque to yield bolts with the MLS gaskets. My understanding or what I have read states that torque to yield bolts in the MLS application favors more consistant pressure over the heat cycles, the reason that non torque to yield bolts in some applications require retorquing after a while depending on the gasket in use.

Since the MLS gasket is a superior product generally speaking, to graphite, composite whatever gaskets, they perform well on properly prepared surfaces under higher than usual stresses. I'm not going to break out the physics book to review metallurgy to defend this idea, but most of us are aware of the purpose of torque plates when boring a cylinder.

With that being said it's not so far fetched an idea that studs and MLS gaskets might be a bad idea or at least very strict when it comes to tolerances as any distortion from the increased clamping pressure be it in the block or the softer aluminum head might lead to a leak problem. Copper gaskets are historically problematic in this area, how much less an even harder material if the surface is not up to spec.

The RA spec for GM MLS gaskets is very low so you can pretty much put your money on a 60 degree motor that didn't come with MLS gaskets from the factory not having a deck and head surface up to par for the MLS gasket even if they are perfectly strait.

[AaronGTR]

On the topic of the oil from the PCV system, I checked it today and there was no evidence of oil in the intake after two days of driving. I think that fix did the trick. I'll check it again on Saturday to be sure. Otherwise, all I can do is put more miles on it and keep an eye on the oil level in the pan to make sure it isn't still consuming oil at an abnormal rate.

[AaronGTR]

Aaron, if you were to order Cometic Gaskets from Summit Racing for a 3800 or any other engine they have MLS gaskets for.... they would not have told you that you must mill your heads either. http://www.summitracing.com/parts/CGT-C5720-066/ Instead, you must read the instructions that come with the product, which you have clearly indicated the slip that came with the gaskets said that the heads must have 50 RA surface finish. If there is something you are not familiar with it is best to try to research it before hand, I understand that you were in a hurry to get the engine back together and consulted with a shop that you thought was reputable. From what I can tell the machine shop did not do several things right and it is possible that they do not have the proper equipment to do the jobs that many other shops are capable of. Their theory on heads having the best finish from the factory, might be true to some extent when they are brand new. Once the heads have been ran on an engine, that theory goes out the window and they should be milled to ensure flatness..... which I personally though was common practice in the engine building community.

Hopefully you will get it back together and not have any other issues, however I would find a new machine shop in the mean time.

sorry but I disagree. You can hardly compare WOT-tech to Summit racing. First of all Summit racing is way bigger and does far more volume, and they also aren't specialized to one engine family like WOT is. They deal in everything and can't give recommendations like that because the same recommendations don't apply to every engine type and gasket type. They also don't sell specialized parts like custom hand ported cylinder heads. Since Ben specializes in one engine type and supports a specific automotive community, you would expect those kinds of recommendations. I think I would know, my brother runs a successful shop specializing in one make of car, and he returns tons of phone calls and emails every week. That's what it takes to keep customers happy and loyal, which is how he makes a living. I specifically asked Ben if I could have his number so I could call him if I had questions and he gave it to me. If he never intended to answer it or if that wasn't the best way to get ahold of him, he could have said so from the beginning. And you know what would happen if you called Summit Racing and asked for a recommendation right? They'd probably tell you to consult a machine shop and go by their recommendation... which is exactly what I did, and apparently Ben thinks was the wrong thing to do.

And yes, I did want to get my engine back together as soon as possible because I had to get my car out of my friends drive way, but I didn't rush things as you are implying. I blew the head gaskets on March 24th and I didnt' even pay for the last of the machine work to get started until May 27th. The engine wasn't back together until June. I had two full months of digging for info and ordering parts to get things ready while I waited for the money to come together. I DID research (since I couldn't get ahold of anyone I trusted for info) and I didn't find anything really relevant. The best article I found was here http://www.aa1car.com/library/ic697.htm and not everything in that exactly agrees with what Ben is saying, so I still don't 100% believe him. The article just says they have to be flat. I asked the shop to check... they said they were flat enough. Like I said though... I don't know what common practice is in the engine building community. This is the first major engine work I've done, so the only way I have to get the info is what the shop says and what the so called "experts" tell me.

[pocket-rocket]

they should be milled to ensure flatness..... which I personally though was common practice in the engine building community.

I have it done to completely stock engines, especially if they have blown a head gasket and especially if they are aluminum heads. It's cheap insurance and I don't like doing the job twice to get paid for it once.

[onefastV6]

Anway, my specific gaskets aren't in the store no... they are similar construction to the Cometic gaskets you do have though, and since you yourself said the same requirements apply for both, it might be helpful to tell that to customers considering the cometic ones don't you think? Sarcasm on the other hand helps no one, and refusing to do something that might help other customers not make the same mistake is just stupid.

And as I said in the other thread, you weren't the only one moving. I also moved AND was dealing with legal issues while in the middle of doing my engine rebuild. I am not and have not blamed all my engine problems on you, but that doesn't change the fact that those gaskets didn't seal up properly because of some information you didn't provide to me. So yes, you could have helped avoid ONE of the problems. I understand you are busy, but you aren't the only one. You are the one though running a store with paying customers who expect some customer support.

Aaron, if you were to order Cometic Gaskets from Summit Racing for a 3800 or any other engine they have MLS gaskets for.... they would not have told you that you must mill your heads either. http://www.summitracing.com/parts/CGT-C5720-066/ Instead, you must read the instructions that come with the product, which you have clearly indicated the slip that came with the gaskets said that the heads must have 50 RA surface finish. If there is something you are not familiar with it is best to try to research it before hand, I understand that you were in a hurry to get the engine back together and consulted with a shop that you thought was reputable. From what I can tell the machine shop did not do several things right and it is possible that they do not have the proper equipment to do the jobs that many other shops are capable of. Their theory on heads having the best finish from the factory, might be true to some extent when they are brand new. Once the heads have been ran on an engine, that theory goes out the window and they should be milled to ensure flatness..... which I personally though was common practice in the engine building community.

Hopefully you will get it back together and not have any other issues, however I would find a new machine shop in the mean time.

[AaronGTR]

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.

Anythings possible I suppose, but I don't think that's it. It didn't show any signs before the orginal gasket failure of excess oil consumption, and there wasn't any sign of oil leaking from the valve guides that time either. Really there was only evidence of oil leaking from one valve guide on the second tear down. I still don't know for sure what caused them to blow the first time, and I may never know. The run that they blew on there was no detonation on my scan, but the run before that showed 2 degrees of KR in 2nd and 3rd gear. The injectors where maxed out and I had seen 2-4 degrees KR on the dyno the week before that. My plan was to run 100 octane unleaded at the track, but they didn't have any when I got there. My best guess is that the gaskets blowing and the bent rod where caused by a sudden detonation, or just from abuse of too much light detonation over too long a period of time.

I'm hoping to have solved that problem with larger injectors, changes to the SC setup, and an alcohol injection kit later if I still need it and can afford it. The MLS head gaskets weren't really needed at my power level. I was just hoping they would be some extra insurance against another blown gasket while I try and get the tuning right. Since I'm back to stock heads and cam and I'm dropping the red line back to stock I'll be at a lower power level and probably won't have to worry about it as much now. Not as likely to have KR.

[AaronGTR]

Aaron... out of curiosity have you had the heads rechecked for flatness since their removal? No one has brought this up but there are two surfaces that need to be in spec for a gasket to seal. Is it possible that the decks aren't flat? With two gasket failures, I wonder if there could be a different issue besides the head flatness. Hopefully, you won't have another gasket failure.

I dropped the heads off at the machine shop friday last week. They said they where going to go over everything again and would recheck them for flatness. I should hear something back by the end of this week.

As for the block, I had that at the shop for inspection as well after I originally tore the engine down and found the #2 piston wasn't coming up to the correct height above the deck. I had them completely check the block and the crank, all connecting rods, etc. They found the #2 rod was bent. Crank was fine, and they said the surface of the block was flat. The piston bores and pistons where both worn though making my piston to wall clearance too high, which is why I had them bore and hone the block .04" over. That was the only machine work done to the block. They cleaned it, put in new plugs etc, and replaced the cam bearings at my request since the old ones were also worn. That was it though.

[AaronGTR]

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.

Sorry you misunderstood what I meant. They asked me what the stock torque specs where and what I torqued them to with the head studs. Basically they wanted to know if I could have severely under or over torqued them. Based on what I told them, they said that 82 ft/lbs with the studs should only equal 15-20 ft/lbs clamping force more than with the bolts. Not a radical difference and not under torqued. That's what I meant... was trying not to write a novel.

Anway, my specific gaskets aren't in the store no... they are similar construction to the Cometic gaskets you do have though, and since you yourself said the same requirements apply for both, it might be helpful to tell that to customers considering the cometic ones don't you think? Sarcasm on the other hand helps no one, and refusing to do something that might help other customers not make the same mistake is just stupid.

And as I said in the other thread, you weren't the only one moving. I also moved AND was dealing with legal issues while in the middle of doing my engine rebuild. I am not and have not blamed all my engine problems on you, but that doesn't change the fact that those gaskets didn't seal up properly because of some information you didn't provide to me. So yes, you could have helped avoid ONE of the problems. I understand you are busy, but you aren't the only one. You are the one though running a store with paying customers who expect some customer support.

[geldartb]

http://foreverpontiac.com/index.php?...20&#entry59531

"I'm am working on fixing the PCV issue today. I can tell you right now it's NOT the piston rings though. He has no clue wtf he is talking about on that one... they are good. I did everything by the book so there's no way they could be bad. Regardless I'll be doing a compression test as soon as I can get a good compression tester, just so he'll shut up about the rings. My compression tester has a bad pressure relief valve and isn't holding pressure like it should."

Yes, I took a guess at what was wrong based on what your engine was doing, and that might not be it. I hope I am wrong, considering you have found 1 source of oil.

yeah i kind of went WTF when i read that. hey shit happens every one makes mistakes every now and then.. i think at this point you have nothing to lose since your taking the engine apart every thousand miles anyway. why not just blow it completely apart instead of playing the oh this didn't work must be something else game.

[Mars]

Honeslty, go with a PCV exhaust slashcut on the rear valve cover and keep the front PCV setup stock. Works WONDERS. I had all kinds of oil leaks before doing this cause I was boosting the case. now, the slashcut sucks it all out and my motor stays clean. I just got the thing from summit.

http://www.summitracing.com/parts/SUM-120108/