Exhaust manifold stud measurement

[gmac78]

Hi Guys,

Silly question here but none the less must ask.

I'm refurbing my 3B head and inevitably 3 exhaust manifold studs have sheared. Not to worry head is off so access is not a problem for repair.

However, the good studs that have been removed measure M8 x 50mm, where as, according to Vagcat they should be M8 x 35??

Now i'm confused as to what size i should order??

Is the 35mm measurement the amount that protrudes from the head when screwed in against the non threaded part? i assume it is but just want to be sure before i order the wrong ones.

Also, should i attempt to remove the remaining 13 studs to replace or leave them as they are as that will no doubt lead to many more sheared studs!!

As always, thanks in advance
Gordon

[UrS4boy]

OE 3B, AAN, ABY and ADU Exhaust Components: a consolidation of info.

Exhaust manifold studs should be M8 x 35 PN N 90188902

http://audi.7zap.com/en/usa/audi+100.../103-103054/#9

Waste studs are M8 x 50 PN N 10169301

http://audi.7zap.com/en/usa/audi+100.../253-253017/#4

*IF* you were installing an RS2 manifold 2 of the studs need to be shortened.

https://www.ecstuning.com/Search/Sit...8902/ES469297/



REFERENCE: OE 3B, AAN, ABY and ADU Exhaust Components: a consolidation of info.

http://forums.quattroworld.com/s4s6/msgs/196904.phtml

[Error404]

Just to complete the picture, can anyone confirm the thread pitch?

[UrS4boy]

Just to complete the picture, can anyone confirm the thread pitch?

They are what they are. Probably 1.5

They are so well used across the VW/Audi program and so cheap, it makes no sense but to replace them anytime the head is off or the exhaust manifold is being changed.

https://www.ecstuning.com/Search/Sit...8902/ES469297/

[martinjs]

1.25 Alex

[Error404]

Cheers Martin. I'm going to get some HT items from my local engineering supplier. Not paying Audi prices for studs!

[UrS4boy]

Cheers Martin. I'm going to get some HT items from my local engineering supplier. Not paying Audi prices for studs!

Just get some "Redi-rod" from Tescos then.

[andy10v]

If you have the head off I would replace them all, if they snap you will hate it, but if the old ones snap when you tighten and its on the car you will hate it even more!

I replaced all my studs with shorter ones



You can get exhaust studs and locking nuts on ebay cheaply, no idea of long term quality though.

[gmac78]

Well, todays attempt at removing the first sheared stud did not go well!!

In between a crying new born baby and recently moving in to a new house with no garage the head work was being tackled on the kitchen floor. Unfortunately no pillar drill in the kitchen either so tackled it with a hand drill, hehe!!!

Needless to say the drill did not go down bang on square, arrrrgh!!! however after many hours of frustration the stud is finally removed, the M8 hole is more like an M9 now, eeek!!. Not sure what to do with this now, perhaps a helicoil or an M9 stud if can find one, perhaps i'll have to make one?

So, the first stud couldn't have gone worse really, well i guess it could have, i could have drilled into the jacket water passages, but still this is a right pain!! If the remaining studs are to shear off a couple off mm below the head like this one did this is going to be a nightmare of a job!!

I really need a pillar drill, not going to drill the other sheared stud in this fashion, too much margin for error.

The studs that sheared really didn't take much force to shear them so i guess they were on the way out. All the other nuts were well soild on the studs, needing heat to aid removal so perhaps these other studs are in much better shape since the didn't shear.

I'm half tempted to leave the other studs but the OCD in me is not liking the thought of two or three new studs mixed in with the old ones.

Oh the joys!!

Anyone else used a helicoil or bigger stud when this job has taken a turn for the worse?

I ordered stainless aerotight nuts today so they should do the job nicely when the arrive, just not sure what to do about the studs now?….

[Kieron20V]

If you've ordered aerotight nuts you really want to be changing them all, aerotight nuts will quickly reveal any weak studs as they have quite a high run on torque. There are stepped studs out there, I'll have a look. You could either fit a stepped stud, probably m10, or helicoil the hole and fit a standard size, either will do really.

Sent from apollo 13 using tapatalk

[Kieron20V]

http://pages.ebay.com/link/?nav=item...269003&alt=web

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[gmac78]

Cheers for the info, i wonder what kind of diameter i can safely open the holes out to? Is opening out to as much 10mm common practice? Also whats the preferred method for removing these studs, or is it the case just hope for the best when unscrewing them?

[Kieron20V]

A helicoil will end up being at least 10mm od anyway. If using one of those stepped studs, you'll need an m10 tap and appropriate drill, just drill it with said drill to clean the hole up and tap it carefully.

Removing the studs, there are various methods, specific tools or just a couple of nuts tightened against each other. For a fighting chance you need to try and get some heat into them and a good blast of wd40 or etc.

Sent from apollo 13 using tapatalk

[martinws]

I'd go with heating the head as much as possible with maybe a blowtorch and try cooling the nuts/studs with air/water or ever freeze spray stuff that plumbers use, with a good dose of WD40!

[Thuppu]

I had two bad helicoil repaired stud holes in one head, so had to tap a M12 thread and made diy "helicoils" out of cutted M12 bolt that I bored and tapped with M8 thread. Quite easy to do with handtools.