Revised lower intake manifold installation 3800

[WrathOfSocrus]

I came across an issue recently which has left me with some questions. My friend has a 2001 Impala 3800. We replaced the motor when he got it and replaced many gaskets including from the LIM up. This was a handful of years ago and used plastic gaskets. I later did another LIM gasket job on a 97 LeSabre when my mother bought the car, knowing of the gasket issues and at that time used the Fel-Pro metal gasket and using Haynes manual torque specs.

 

Fast forward to today when my friend tore apart the intakes on the Impala to find trouble with the LIM itself. After sitting for ~2 years, the car had even more problems than when it was parked. The LIM gaskets were plastic on the outside with whatever synthetic rubber gasket in the middle and more plastic in the middle. This plastic swells and bows inward, pulling the gasket material with it. I guess from the car sitting so long, the nasty old coolant eroded the LIM around one of the coolant ports and had to be replaced because it would never seal again.

 

Today at the junkyard while grabbing an injector the car had aluminum LIM gaskets which turned out to be the Delco's. Now these Delco gaskets have the same fatal flaw as the other gaskets! They have plastic on the inside around the ports that showed swelling around the coolant ports. It has been so long since I did the Fel-Pro's on the LeSabre that I don't remember it having plastic inside, and I can't really tell by pics, it just looks all black.

 

So here is the burning question - Is there a change in torque spec for the metal gaskets? I know on the 3500 LX9 it had little metal inserts around the bolt holes to avoid over torquing, but I really don't remember if they changed the torque spec there either. The car we unbolted at the junkyard had bolts on fairly tight (no thread locker), whereas all of the other LIM jobs I have done had many bolts roughly finger tight (if that). I wasn't sure if maybe there was a revision to the torque specs along with the new gasket design. I see there is a TSB 634708 revised lower intake manifold installation. However, I only see the heading description and everywhere I look I don't see the details. I have searched around a bit trying to find information, but everyone is using the same torque, many quoting the same Haynes manual as I used when fixing the LeSabre. Without knowing the details of the TSB, I can't be certain that this isn't going to be happening again. I would rather get both these cars squared away now with the right gaskets and torque specs and not have to deal with coolant getting into these engines. If anyone has access to the TSB and can tell me what it says, if anything, about the torque specs, then it would be greatly appreciated.

[Nas Escobar]

The LIM torque spec is 10ft lb. You're actually supposed to torque em in ft in but since I had no access to that tool, I converted the inches to pounds.

 

The metal gaskets are not supposed to do the same thing as the plastic ones. The plastic ones usually mess up and lose shape, if the metal ones do this, then the intake valley area is not flat and needs to be checked but I've done this job twice and I've never had issues with it. You are also supposed to use a torque sequence on the LIM, don't criss cross.

[WrathOfSocrus]

Well I checked out the Fel-Pro gaskets today and they don't have the plastic crap in the center like the Delco's do. This is a great relief that I don't have to replace the ones on the LeSabre. I had my friend get the Fel-Pros today and got it done. Back when I first replaced the engine in that car years ago I bought a torque wrench that has in/lbs and Nm graduations for about $130 at Summit. I used it today and printed out a page with the bolting sequence and torque specs. I just wish I knew what was on that TSB. GM is the one that failed and then they make changes to the repair procedure and keep it to themselves.

 

I know the new gaskets aren't SUPPOSED to fail, but then again the originals weren't supposed to either. Every car that I have seen with the LIM gasket failure had the same situation - the very center of every port has a thin (~1/8") plastic ring around the port, followed by the gasket material (some synthetic seal). This inner plastic bends inwards when it swells after years of heat and pulls the gasket with it causing failure. The Delco metal gasket still has this feature! I would tell anyone debating which one to get that there is no debate - It's Fel-Pro or no go.

[Nas Escobar]

Yeah I was thrown off by the whole ordeal because I've never heard of a Fel-pro metal gasket fail. The S3 gaskets weren't known for issues interestingly enough and they have the Delco gaskets.

 

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[WrathOfSocrus]

I believe it. It is certainly a much better design. They have metal where it would take gorilla force to over torque it, and the gasket I saw wasn't completely trashed. But the Delco I saw was definitely showing signs that it was distorting around the ports. The Fel-Pro gasket is just engineered better. I am still curious about the changes to the LIM installation by GM. I guess I will dig around some more and hopefully find out what the TSB says.

[mfewtrail]

I don't believe any torque specs changed on the 3800's. If using a Fel-pro gasket, use their installation instructions/torque specs. Do you happen to know the TSB number?

[WrathOfSocrus]

'TSB 634708 revised lower intake manifold installation' is what I came across when searching info about the metal gaskets. It's possible nothing significant changed, but I don't understand why this information isn't made easy to find without having to shell out for it. There must be something of value there, otherwise they wouldn't have bothered to make a TSB about it. Unless it is simply a warning not to use old stock plastic gaskets. I am just curious to find out what it says.

[mfewtrail]

'TSB 634708 revised lower intake manifold installation' is what I came across when searching info about the metal gaskets. It's possible nothing significant changed, but I don't understand why this information isn't made easy to find without having to shell out for it. There must be something of value there, otherwise they wouldn't have bothered to make a TSB about it. Unless it is simply a warning not to use old stock plastic gaskets. I am just curious to find out what it says.

 

That bulletin number is for cars with the 3100, not 3800.

[WrathOfSocrus]

Can you direct me to some place where I can look up TSBs for myself?

[mfewtrail]

Can you direct me to some place where I can look up TSBs for myself?

 

I don't know of any place online to do that, at least not for free.

[WrathOfSocrus]

OK, thanks for the help.