Proper LIM torque with Felpro perma dry 98004T.

[MikeHoward]

Felpro gasket 98004t set. I have a 1995 3.1 chevy lumina car. L82 small port stamped rockers. I can not believe with all the write ups on this problem I cant get a rock solid concrete answer. The felpro info vaguely says torgue to spec! The haynes manual says 18 ft/lbs. This site if I am correct recomends for L82 small port 115 inch/lbs. all bolts center and angled outer. I also see 115 inch/lbs center and 18 ft/lbs outer for what I gather is the newer lg8 "big port". Can one of the experts here please set the record straight and place the info into stone. Thank you MH.

[Google Adsense]

[SappySE107]

These are the instructions for our ported manifolds, which are the exact same spec as all 3100, 3400, and 3500 lower intake manifolds. The upper has more bolts on the 94-99 small port 3100, and there are no torque specs or sequence from GM. It is recommended to use the same technique and specs in the attached pdf.

Manifold Set Torque Procedure.pdf

[19Cutlass94]

Ben, that 18ft/lbs on the UIM for the large port motors is a bit much. I used a torque wrench on mine when putting it back together after the injector swap, and I got MAYBE 10ft/lbs before the UIM started to crack. Ever since Ive just put those bolts snug and called it good.

[SappySE107]

Did you start from one side, 18 ft lbs, and work your way around? That might cause it just as much as tightening the lower intake from one side to the next rather than working inside to outside. 5 ft lbs would likely do the job but 18 is the spec from everyone and we have revised it ourselves to make sure the pattern is done and that it isn't fully tight on the first pass.

[19Cutlass94]

Yes, I followed any tightening sequence that you would on any cyl head, LIM, UIM etc etc. Started cracking around 10ft/lbs from what I could tell on the wrench. Started on the inside and worked the way outward. I did not go 18ft/lbs right off the rip. I slowly worked the ft/lbs up as I went. First pass was about 5ft/lbs and increased it with every pass. So I settled on just putting them snug

Im just bringing this up cause I dont want to see anyone break their's. Especially if they have one ported and such. Between porting and powdercoating, I have $300 in the UIM, and thats alot to break off the tabs and not able to bolt it on anything anymore.

[MikeHoward]

Ok. Thank you very much for the info. May I ask though if I read the spec right the center inner bolts are torqued to 115 inch/lbs or roughly 9.5 ft/lbs. the outer angled bolts are torqued to 18 ft/lbs. WHY or what is the theory behind the difference in torque between the center bolts and the outer bolts? Ive been turning wrenches for along time now and have done too many intake manifolds across all makes and models and cant really remember an uneven torque spec. Pardon my skeptism but along with probably ruining my beautifully running 1995 lumina by poor GM engineering I just had the plastic!!!!!!!!!!!!!! intake on my 2002 3.8 impala explode and catch fire. I hope the so called engineer who was in charge of maniflold design for GM is been fired or worse. The 3.1 and 3.8 are great engines but these decade long manifold problems are ridiculous and uncalled for. To me the bolts holding the 3.1 intake down are grossly undersized and too small for the job and plastic to contain explosions on an internal combustion engine come on! REALLY. MH

[SappySE107]

The diagonal bolts apply pressure from the manifold to the head itself, and the vertical bolts apply pressure on the silicone strips to seal the valley, and align the diagonal bolts to the head. That would explain the difference in torque spec, as they don't apply pressure to the same surface.

Can't say I understand why you think a plastic manifold should contain explosions from an internal combustion engine, because any properly running motor will have those "explosions" in the combustion chamber. Many cars have composite manifolds for weight reduction and less heat transfer.

[3100]

Composite manifolds are a problem when you're backfiring. Lots of Ford modular V8s had manifolds blow apart.

[MikeHoward]

That thin cheap plastic overly cost conscious manifold evidently warps over time and causes the engine to miss and not run properly. The MANIFOLD caused the misfire and couldnt contain the explosion. I came so close to having my 14 year old daughter crank the engine while I investigated the problem which would have most likely put my face inches from plastic shrapnel and flames. Had that happened I would sue GM into its next bankruptsy. Google it. Its happened to others and in my mind should never happen. GM also went to a metal manifold later. There is a recall on the problem I need to investigate. I guess some swap the plastic for the newer metal manifold. Cant beleive you seem to justify it. The plastic or composite is too thin to contain the misfire. Also it was cold that night propably 20 degrees making it more brittle. But as I said I dont think that should ever happen. MH

[19Cutlass94]

umm... 60*'s dont have plastic manifolds so whats it matter? If your car is that fucked up, fix it! You dont like GM design, buy another car. This is about torque spec on cast manifold. Not about plastic manifolds that these 60*'s dont even have...