torque specs for engine mount bolt for 911 sc

[kj9438]

hi guys , i want to change my old worn rubber engine mount and i like to know when i reinstalll the mount back and tight the bolt , do i need torque wrench to tight bolt into any torque specs or i can just use normal wrench just to tight it ? and if i need to tight to specs what is the specs . thank you

[JJ 911SC]

Well if you want to do it to the specs; its 25 Nm (18 ft-lb) and you will need a Torque Wrench

[Peter Zimmermann]

Are you asking about the two small 8mm bolts (18 lb/ft), or the big, long, 12mm bolt (65 lb/ft) that holds the engine in the car?

[JJ 911SC]

Peter

Was about to made that distinction. The specs book has the M12 bolt @ 80nn (58lb/ft).

Also, it does not help that the Bentleys books has a mistake as they have both the 8mm bolts & the 12mm one at the same torque for the Transmission Mount: 80nn (58lb/ft). They do got it right for the Engine Mount.

[Peter Zimmermann]

The "book" aka Spec book, can be sketchy on that 12mm bolt's spec, but I had the distinct advantage, in 1975 as a P-car dealer tech, to attend multiple Porsche factory tech seminars in Culver City, CA. That is where I learned to use 9 kpm, kilopondmeter, (9 x 7.23 = 65 lb/ft) - which, co-incidentally, is the same spec for the 8.8 grade, 12mm x 1.5 thread bolts that hold the aux. front carrier to the body. Easy to remember! Used that spec for thirty years, never had one come loose, never bent an engine mount "spear" during dis-assembly!

[Bob Kontak]

Mr. Z is correct.

[JJ 911SC]

Originally Posted by Peter Zimmermann

... but I had the distinct advantage...

Peter

What you mean I had, you still have

By the time I thinking I'm at 58lb/ft, the torque is more likely 65lb/ft if not more...

I'm only been doing mechanical stuff since I got the car but looking at Bentley I knew there was something wrong with their number, same torque for the 8mm and the 12nn did not make any sense. Only after I did a posting about it I find out that it was a "typo".

Cheers

JJ

[kj9438]

thanx guyys.

[kj9438]

is that ok to tight bolt with out toque wrench? or must use toque wrench

[JJ 911SC]

No if your wrist break at 25 Nm (18 ft-lb) otherwise yes...

You must know someone who has one?

[911pcars]

Careful. If there's a way to counter-hold the mount bar threaded area when tightening/loosening, do so. Otherwise, cw or cc torque places undue stress on the mount bar end and can cause it to bend and/or fail.

I would suggest drilling through the mount bar to delete the existing threads, then use the previous nut, bolt and washer arrangement (as in early engine mount bars) to attach to the motor mount.

Sherwood

[Peter Zimmermann]

Originally Posted by kj9438

is that ok to tight bolt with out toque wrench? or must use toque wrench

JJ is correct! Always torque critical fasteners. The two 8mm bolts are not as crucial, and do little more than locate the mount, so "tight" is tight. The 12mm bolt holds your engine in the car! The larger the bolt diameter, the more difficult it is to "feel" when tight is tight. To make sure that your engine doesn't fall out of the car, and to prevent damage to the cross bar, aka spear, either during install, or removal at some point down the road, always torque those fasteners.

[Bob Kontak]

Originally Posted by 911pcars

Careful. If there's a way to counter-hold the mount bar threaded area when tightening/loosening, do so. Otherwise, cw or cc torque places undue stress on the mount bar end and can cause it to bend and/or fail.

Very interesting. My pals 89 had a broken mount bar on the passenger side when he bought it. At the skinny part of the neck. Porsche dealer PPI missed it but that is moot.

So we find it and he buys a snappy Rennline one and goes to remove the long fat bolt near where the cross mount broke and it is not moving. Monstro breaker bar - nuttin' is going to move that bolt.

I bet your warning had something to do with that mount breaking. Over-torque, cross threading, who knows? If engine torque caused it to break I don't see that causing the threads to seize.

[pharlap71]

First time I pulled the engine in my '84 I noticed the top of the heads had red paint, when I tried to losen the bolts you would not believe how tight! I couldn't beleve it, the round bores on the bar broke off, I had to use vice grips to hold them to remove the bolts, they were not stripped or cross threaded, just tight. I don't know how they got them so tight without stripping the threads.

[911pcars]

Originally Posted by Bob Kontak

Very interesting. My pals 89 had a broken mount bar on the passenger side when he bought it. At the skinny part of the neck. Porsche dealer PPI missed it but that is moot.

So we find it and he buys a snappy Rennline one and goes to remove the long fat bolt near where the cross mount broke and it is not moving. Monstro breaker bar - nuttin' is going to move that bolt.

I bet your warning had something to do with that mount breaking. Over-torque, cross threading, who knows? If engine torque caused it to break I don't see that causing the threads to seize.

Bob,
Forgot to add that a dab of anti-seize on any fastener thread does wonders to reduce frustration and parts damage at a later date. The rear engine mount bolts are probably installed dry @ the factory and stay in place until the first engine drop, typically many years later, giving that joint plenty of time for corrosion to take place. The problem with that setup is that all the force that results in removing the stubborn bolt is concentrated on the weld joint at each end - whereas a nut can be better held with a wrench/socket.

Sherwood

[JJ 911SC]

Originally Posted by 911pcars

Careful. If there's a way to counter-hold the mount bar threaded area when tightening/loosening, do so. Otherwise, cw or cc torque places undue stress on the mount bar end and can cause it to bend and/or fail.

I would suggest drilling through the mount bar to delete the existing threads, then use the previous nut, bolt and washer arrangement (as in early engine mount bars) to attach to the motor mount.

Sherwood

Sherwood

When I first read your post I "mentally" dismissed you suggestion.

A couple of day later, I received this one from another Pelican (bought as "you never have too much spares if the price is right") and notice how straight the bar was and it trigger my memory that when I drop my engine one end of mine was bent enough that the "hole" actually line up with the side of the bar vice in line dead center. That bend is counter clockwise so it was probably me that did it when I undo the bolt.

Well I guess the "spare" one is going in and will use a counter hold blocker while torquing.

Thanks

J.J.