Fastener Size Question-C3 EGR Studs

[Paul Latour]

I am in the finishing stages of restoring a 1979 #14007378 aluminum intake manifold. The only item left is the EGR studs and nuts. GM Canada says discontinued (as usual). So I checked for size. That came back as 1/4-20 x 700. That looks like a 1/4" diameter stud with 20 threads per inch. But the 700 length threw me. Canada is a semi-metric country so I have concluded that GM has gone inches and metric in one breath. The 700 may be mm (or 7.0 cm) which translates to about 2 3/4". Does that make sense? If yes, where can I get a couple of studs with those dimensions? Thanks.

[Joe L.]

Re: Fastener Size Question-C3 EGR Studs

Paul-----

The EGR valve flange was secured to the intake manifold by either bolts or studs/nuts. Depending upon application, one or the other was used. I'm not certain, but I think that your application might have, indeed, used studs.

When bolts were used the length was about 1-1/2". For studs, the length should be about 2". However, I don't think that the thread size is 1/4-20; I think that it is 5/16-18. With the studs, one end of the stud was 5/16-18 (NC) and the other (the end for the nut) usually was 5/16-24 (NF). Check the size of the threads in your manifold to confirm that they're 5/16-18.

Studs of this sort are usually easily available in auto parts stores. Of course, I don't know if that's true in Canada, or not. However, since many US cars have English system fastners I would think that you could find such items in Canada. Usually, auto parts stores that have the orange "Dorman" brand "drawers" with all sorts of fastners will have one or two drawers full of various size studs.

I may be able to provide GM part numbers for suitable studs later, but I will need you to confirm the manifold thread size and the TOTAL thickness of the EGR valve flange + gasket.

[Paul Latour]

Re: Fastener Size Question-C3 EGR Studs

Joe,
As with my rad post, I am stuck. My car is in storage. But they are definitely studs: I replaced the EGR several years ago and remember that very well. I put the existing studs in with anti-seize so they may come out very nicely. And can be used again or for comparison purposes.