carb studs thread

[andrewo]

Just installed new carb studs, since the had decided that bolts would be an adequate solution. When I went to the auto parts store, I did not notice that the studs are different thread pitches on the two ends. I installed them with the short end (coarse threads) in the intake manifold, but now I can't figure out what size nuts to use to hold the carb on. M8-1.25 looke right, but are not turning easily, and I am concerned about damaging the thread.

Does anyone know what size these are supposed to be?

Andrew

[MICAH1]

I just did the same thing. I purchased my carb studs and nuts as a package at the Auto Zone. The nut size was 1/2 inch.

[tekenaar]

Originally posted by andrewo
Just installed new carb studs, since the had decided that bolts would be an adequate solution. When I went to the auto parts store, I did not notice that the studs are different thread pitches on the two ends. I installed them with the short end (coarse threads) in the intake manifold, but now I can't figure out what size nuts to use to hold the carb on. M8-1.25 looked right, but are not turning easily, and I am concerned about damaging the thread.

Does anyone know what size these are supposed to be?

Andrew

Stock it's M8x1.00.

[kwilford]

I assume it would depend on what studs you bought. As Otto says, the bottom (manifold) end of the stock stud is M8x1.25, and the top (carb base) and nuts are M8x1.0. But you may have bought studs that were M8x1.25 on both ends, as that is more common. In fact, my quite extensive tap and die set doesn't even HAVE an M8x1.00 tap or die. Do you have a thread pitch gauge?

[andrewo]

I don't have a guage, but I think Otto is right. I got the studs from USA Opel and forgot to order nuts. When I went to the Kragen up the street, I think that the guy t the counter checked the nuts against the manifold side. Its not really his fault, since I didn't notice that they were two different threads until after I installed them, and the nuts didn't fit well.

Andrew

[Willy_g77]

im confused.. if sock is m8 x 1.25 at bottom and m8 x 1.00 .... then what would you use for a weber carb? becuase the stock ones are to long correct?

[namba209 (R.I.P.)]

It's really simple Billy, just get shorter studs with the correct threads on each end. Most studs have an area of no threads and it can be a longer or shorter length of non threaded area depending on the need.

[kwilford]

I'm confused.. if stock is M8 x 1.25 at bottom and M8 x 1.00 .... then what would you use for a weber carb? because the stock ones are to long correct?

Willy, you have a couple of choices.

You can cut the stock studs down. But that can be tricky, as it is difficult to cleanly cut the stud without removing it first. And removing it requires you use two of the fine-threaded nuts (back AWAY from that vice grip, Billy!) as "jam" nuts, and these fine nuts make TERRIBLE jam nuts. Then the stud has to be cut so that there is just enough sticking above the carb base (with all the gaskets and heat shield in place) to fit a lock washer (the wavy spring type are best) and the nut, with just a few threads protruding. Too long, and the stud interferes with the carb body. Too short, and you won't get the nut on properly. And even then, the fine thread is quite prone to cross-threading, so unless you get the top threads JUST perfect, it can be difficult to get the nut started properly. If you cross thread the nut, then you are hooped, because these fine threaded nuts can only be bought from a speciality fastener shop, and same with the M8x1.0 tap and die (if you can get them at all).

Choice number two is to buy a standard M8x1.25 stud of the correct dimensions, or even cut the head off an all-thread bolt to the correct length. Then you don't care if you take the vice grips to the old studs, since they are heading to the bin anyway. Even if you have to cut down a standard stud or bolt, the M8x1.25 thread is much more forgiving to start than the M8x1.0, so there is less chance of cross threading. And standard studs (and bolts) are available in stainless steel, as are the washers and nuts, which is a bit of the "cool" factor. Just make sure that the threads in the manifold are in good shape (or install thread repair coils) and also use Lock-Tite to hold the stud into the manifold.

JM2CW

[jerseyopel]

Willy, the dimensions they gave you on the studs are not for length.

[tekenaar]

It's really simple Billy, just get shorter studs with the correct threads on each end. Most studs have an area of no threads and it can be a longer or shorter length of non threaded area depending on the need.

You're ALL making a mountain out of a molehill here, IMO. Look outside the box for a moment. Most hardware stores carry spacers of various lengths, some even chromed. I've always just used four ~1/4" long, 5/16" spacers when converting to a downdraft Weber. Simple, effective and you don't change a thing!