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Vacuum Advance Pipe

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WHT

WHT

Jedi Hopeful
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Hi,

I have a question about replacing the distributor vacuum advance pipe. As you know, the pipe is help in place with a clamp/bracket that is attached by a head stud nut. I am concerned that removing a head stud nut to replace the pipe could initiate a head gasket leak; and I should not tempt fate and find another way to attach the pipe.

Is this a groundless fear? Is it OK to remove the nut for line replacement, and then re-torque the nut?

Thanks.

Regards, Bill
 
I am not an expert engine builder although I’ve done a few. I would not touch the head bolt nut. My opinion is that the vacuum pipe clamp should never have been under that nut to begin with. The clamp is soft metal and I don’t see how you could get a proper torque on the bolt with that clamp in place. My vacuum line just suspends freely because it is not fastened to that bolt. It makes the line a little wimpy because of that but it has been that way for at least 20 years.
 
Agreed with Vette. The pipe clamp is suspended above the head bolt. Every so often I'll attach it to the 2 protruding threads of the head stud, but it pops off soon enough. No harm, the pipe does it's job just fine.
 
Thanks Vette and Gonzo,

Those were my thoughts, also. It looked like a poor design to me and there has to be a better way to install/support the pipe without molesting the head studs.

However, being new to the BJ8, I wanted to check with more knowledgeable owners.

Regards, Bill
 
I think it would be okay to temporarily loosen (remove) the one nut in order to change the way the bracket is clamped. This is no different than retorquing the cylinder head by alternatively loosening and tightening the nuts in the pattern suggested. The engine will not know that you are temporarily loosening (removing) the one nut for a different reason.
 
Thanks Michael,

You are probably correct. However, I am not sure I want to take the risk now (it’s the best part of the driving season).

FWIW, I have decided to re-route the line so it is more convenient and better for the soft copper pipes available today (they flex more than I like even when supported). I might try to buy some “soft” 1/8-inch OD 304 stainless steel tubing and bend a new pipe as an experiment.

I am also looking at hard plastic, heat proof tubing as used on later British car distributor advance lines. A shorter, more responsive line could be routed over the valve cover and easily replaced when you need to remove the cover. 1/8-inch OD plastic lines are available with similar ID/volumes as the original steel pipe, heat proof to 250F and good for 29-inches working vacuum. Better living through chemistry (maybe?).


Regards, Bill
 
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