Carburetor Mounting Studs

[Steven A.]

The Holley carburetor on my 1966 327/300 is currently mounted to the manefold with bolts. It appears to me that it is suppose to be mounted with studs and nuts. A search of prior posts indicates the studs are 5/16th x 18. I assume the 18 refers to the finest/courseness of the threads. So my questions are:

(1) how long should the studs be?

(2) are these a regular "hardware store" item or are these made to special automotive specs?

Thanks.

[Ralph E.]

Re: Carburetor Mounting Studs

Go to your local chevy or auto parts store and get the right one. The threads in the manifold are different that the bolt threads.
Ralph #37280

[Gene M.]

Re: Carburetor Mounting Studs

Steve, the studs are generally 5/16-18 into the manifold and 5/16-24 (fine) for the nuts securing the carb. Typical finish is black oxide but zinc plated are also used. I don't recall the overall length but the nut as tightened will have about three complete threads extending beyond the nut. No washer was used by the General.

[Mike M.]

Re: Carburetor Mounting Studs

Go junk-yarding for the original type studs which are fine thread and coarse threded and they usually have a small dimple in the exposed end of the stud. any GM product built in the 60 and 70s that used Holly cars should donate the studs you need.mike

[Joe L.]

Re: Carburetor Mounting Studs

Steve-----

The original studs for your application were GM #3829011. These studs had 5/16"-18 thread for the manifold end and 5/16"-24 thread for the nut end. They were 1-53/64" long. These studs were discontinued in September, 1972. If you want originals, do as Mike says and go hunting them up in self-serve salvage yards. Many were used on a variety of applications. Also, studs found in automotive parts stores (often in the orange Dorman bins) will be just about as close as you can get.

The current-day GM replacement for the 3829011 is GM #333959. It's still available to this very day for about 3 bucks, GM list. This stud has the same 5/16"-18 and 5/16"-24 threads on either end. It's 1-15/16" long which makes it just a "tad" longer than the original. The reason for this is that this stud has a reduced-diameter, unthreaded extension on the upper end for the purposes of locating the nut and making getting it started easier. What will they think of next?

[Steven A.]

Thanks to all *NM*

[Craig S.]

Re: Carburetor Mounting Studs

Joe - handy for the mechanic or assembler though, speed nutting the carb!....maybe they were thinking of a NASCAR carb change... Craig