I just finished replacing valve cover gaskets on my 3rd gen. When I started the engine, there was a fairly loud high pitch whistle or squeal. I finally found That the noise was coming from a slight vacuum leak where the two halves of intake manifold meet up. I used new gaskets but the bolts had slight oxidation on them which I cleaned with a wire wheel On my bench grinder. When I installed the bolts, the threads were so dry that they really didn’t want to keep tightening when approaching torque spec. therefor I feel like they might not have been able the be tight enough to pull the surfaces completely together.
Is it recommended to lubricate the bolts to facilitate achieving proper torque?
Thanks much!!

No. Torque to 53in pounds, starting in a criss cross pattern in the center and working out.

My Haynes manual says torque for intake manifold is 13 ft. Lbs. which converts to 156 in. Lbs.
and that 53 in. lbs. is for valve cover bolts.
I wonder if the FSM shows the value you recommend & that Haynes is wrong?
Thanks so much for your reply & input!
Tom

My bad, the 53 inch pounds is for the valve covers, not the intake manifold. 13ft pounds for the intake manifold. But no, I don’t see any reason for the need to lubricate the bolts unless someone else has been in there before and gotten overzealous tightening them.

Putting anything on the thread will throw off torque readings

Inspecting all the nuts and bolts 4 messed up treads, cleaning the bolts off with a wire wheel and blowing the hole out before reassembly is a good practice to get into. There is nothing wrg with putting a little lube on the nuts and bolts. (it will not throw the torque off.... what it does is allow u to get an even and consistent pressure along the mating surface). I didn't say lather the bolts, a little lube goes a long way. The OP is most likely correct in his assessment with what is happening. This goes with head bolts as well, I only bring this up as i have read a # of threads trying to say u can't lube head bolts (ARP has lube specifically for said 4 the reason i stated above).

Non copper containing anti seize, or silicone grease ect... Copper containing can not get along with aluminum sometimes.

Lube does change torque, but generally not outside of spec range. Corroded bolts also throw off torque.

Snug should be enough to seal the intake though. Might be there is an underlying issue.

The only thing the lube changes is an even and uniform pull long the threads and doesn't not change the torque value.

and i agree there there maybe some other underlying issue ie an warped main or impropriety clean of the mating surface.

Sorry to derail the thread, but lube most definitely changes the preload to torque relationship. Depending on the lube, you can change the preload by a factor of 5 or more when you go from dry threads to lubed threads. So if you want the same preload as you had with dry threads, you'd need to lower the applied torque accordingly.



Lubricated Bolts and Reduced Torque

You are correct that lube makes torque to preload relationship more consistent, which is why the more critical fasteners (head bolts, connecting rod bolts) specify torque for lubed threads. But that relationship will be completely different than for dry threads.

Having said that, it is possible that the acceptable preload range is insensitive enough to this variation for the intake bolts. But I would not lube the threads and apply the same torque as for dry, I'd cut it down to at least half.

Loen, u didn't derail anything, u added great content to the thread, correct me if i am wrg here but the table isn't completely across the broad because the preload to torque relationship also depends upon the diameter and pitch of the bolt and with the intake bolt/nut surface and the net gain in negligible at best?

NGK specifically put out a service bulletin about not putting anti seize on threads of their sparkplugs because it overtorques them and can pull the threads out of the head.


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I use anti-seize lube on almost anything that doesn't get locktite. It a good idea when torque accuracy is important. So is cleaning the threads well. Also important when putting steel into aluminum

we r not talking about putting anti seize on anything, anti seize is a completely different animal, and i would never put or recommend putting said on sparkplugs... so not sure what ur point is to my reply to 4runner4leon.

Cool, glad you found this helpful! The table is applicable across the board in that regardless of the bolt size, preload will be higher at a given torque level if you change from dry threads to lubricated threads.

Now if you want to try to actually calculate the preload at a certain torque level, then the bolt diameter comes into play. But all else being equal, the preload will change by the values shown in the table (or more) when you switch from dry to lubricated threads.

I’m sorry then, But, when you said negligible at best I thought you meant that there isn’t much of a difference between using it and not using it.

IMO there is a difference when using it on bolts or spark plugs. It’s still threading into soft aluminum. It’s still a lubricant like oil, grease, WD40.......

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