Intake Manifold Bolt Size and Recommendation...., I had one wiggle out before...what is the required size and style? Options

[second wind]

Hello all,
Thank you Sir Andy and Superhawk for getting my login working again. So I had a intake manifold bolt come out on the SLO WCR and my car was overheating big time. One of the guys took me to his shop with lift and he discovered the missing bolt. We found one that worked on his workbench but I had another 914 brother tell me there are special bolts for this application. Could someone please tell me the correct size and dimensions I need to replace the bolt correctly and is there a cure for it becoming loose again? That you all and Happy New Year to everyone.
All the best,
gg

[Superhawk996]

I assume your talking about the stud that is in the head and then the manifold attaches to that with a nut.

Here’s the deal. There is nothing special about that stud. It’s plain steel. Grade 8.8

If a regular hex bolt was used in a pinch in an emergency that is fine and will not be a problem. Sure it would be good to replace it with a stud but it’s not a must do immediately kind of thing.

The stud is just a M8x1.25 that is 35mm long. AA sells them for about a buck apiece.

The only secret to keeping a fastener from loosening is to torque it properly. Split ring lock washers are useless for “locking” anything. I don’t have the torque spec off the top of my head. Should be in Haynes or factory service manual. You could use a drop of blue Locktite but in reality the heat from the head is going to negate some of the effectiveness of the locktite. Sort of the same for a Nylock nut - the temp of the head will tend to soften the nylon and it won’t grip the stud. You could potentially find an all metal prevailing torque nut somewhere like Belmetric but it really isn’t necessary and might be hard to find. Best to just use a torque wrench and tighten it to spec.

@second wind Good to have you back on-line!

Torque is 5.9 Nm

[Superhawk996]

Looks like Pegasus has the prevailing torque flange nuts. This would let you ditch the useless lock washer and still get a good base to contact the manifold runner and have a prevailing torque nut.

The thing that will negate the effectiveness of this solution is that the stud will not be locked into the head as securely as this nut will be to the stud. It could still loosen at the head and the next time you need to remove it, you can virtually be guaranteed that the nut & stud will come out of the head as an assembly rather than just being able to remove the nut.

Here for consideration but personally I wouldn’t go this route.