smog pump removal - what length chain cover studs?

smarjoram · smarjoram's Garage

Hello

I'm going to remove my disconnected smog pump - it doesn't seem to be necessary in the UK.

Apparently I'll need to replace three of the studs in the chain cover for shorter ones.

Does anyone know the part numbers for the studs on a car which has had the covers upgraded with hydraulic chain tensioners?

Also, how do I remove the old ones and fit the new ones? Will the covers need to come off?

Also also, when I blank off the injector holes with the grub screws should I use a special sort of loctite?

Thanks for any help.

Glasgow 911SC · Glasgow 911SC's Garage

I removed mine but didn't replace any of the studs. I just removed the original ones using 2 nuts on the stud. Tightening one against the other with spanners moves the stud out. I've still not removed the injectors so the plugs haven't been installed yet. I just blocked off the pipework.

smarjoram · smarjoram's Garage

You are going to replace the studs though aren't you?

Jdub · 03-11-2003, 05:54 AM

You have just made me aware of a total screwup on my part. When I pulled my smog pump I simply covered the threaded studs (three) with clear vinyl tubing to prevent the threads from being damaged.

I guess I should thread nuts on those studs to keep the cover tight?

John

smarjoram · smarjoram's Garage

As I understand it - either you should use a spacer made of a soft metal (so as not to damage the casing) or replace the studs with those of the correct length.

Glasgow 911SC · Glasgow 911SC's Garage

I wasn't aware that those studs were necessary to keep the cover tight!? I assumed, because the other side doesn't need them, that the pump side wouldn't either??

smarjoram · smarjoram's Garage

Well I'm not sure - I could be wrong. Perhaps someone could post a picture of the cover after the pump has been removed. I can't quite work out from looking at mine which studs it would be.

Jdub · 03-12-2003, 05:14 AM

It seems to me that if you can tighten an air pump via studs to an unsupported timing cover section than that is either a bad design, you must respect the torque values religiously, or it is supported in some way I cannot understand.

In all events, I will thread on two nuts per stud. One at the proper torque value and the next to lock that nut.

John

Glasgow 911SC · Glasgow 911SC's Garage

T
John
What size are the studs? Maybe I should get some bolts or studs on the top 2 holes.

Jim Sims · 03-12-2003, 10:38 AM

From an old post on this topic:

You can make spacers out of pieces of metal tube or install the correct length studs. The correct studs are BM6x42 (6mm x 42 mm long); Porsche Part no.: 900.061.092.02. If you elect to go the spacer tube approach put a washer on the front and back of the tube so the tube doesn't "dig" into the soft magnesium or aluminum chain case cover and so the nut has adequate surface to bear upon. You can make a stud out of 8.8 (numbers are formed on head) grade 6mm hex head cap screws (saw off the head and dress up saw cut with a file) if you can find them with enough thread length. Remove the old studs by "double nuting" the end or by using a stud collet. Install the new studs with red loctite on the portion of the threads that screw into the chain case. Do not be tempted to just install screws in place of the studs as everytime the screw is removed/tightened in future the threads in the soft magnesium or aluminum are worked and they'll wear out or fail. Save your air pump parts as you or a future owner may need them someday and they will be hard to replace. Cheers, Jim

Jdub · 03-12-2003, 11:08 AM

Beautiful. Thanks Jim.

John

smarjoram · smarjoram's Garage

I read Jims advice before - thanks for that. I rang the local Porsche dealer who said that the studs had a new part number (I don't have it to hand at the moment). But when i looked on my PET catalogue I couldn't find studs of the same size or part numbers that matched. I'll see if I can post the diagram and maybe one of you could point out which ones it would be.

Could it be that there are different length studs on cars with hydraulic chain tensioners?

Cheers - Stefan

3noses · 04-27-2013, 09:36 AM

I just finished removing my air pump on the 78 SC, and have discovered the 2 studs that need to be replaced on the top of the cover after the pump bracket is off -a struggle- are size 8MM x 50mm, not the smaller 6mm as are around the rest of the timing chain housing.
Sourced for $1.56 each, I found them at a company called Bel-Metric.com, along with the matching metric nylock nuts to fit.
Hope this updated info helps.