1970 Corvette w/4bbl Q-jet air cleaner STUD

[David L.]

Pictured below is what I believe to be a 3921975 air cleaner stud (1/4"-20-20 X 3.5", 1.25" & 0.60" thread lengths) as well as a NORS 3785256 stud which you "cut to fit". Both studs have a "blunt/pointed" top end. I buffed the 3.5" stud with my wire wheel to remove the very light surface rust.

Did the factory installed 3921975 air cleaner stud have a black oxide finish like the NORS stud?

Dave

[Rich C.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

I have an N.O.S. stud, in the original bag, it isn't black oxide. The one I have if memory serves, the light 'goldish' look that most the other carb parts have. I'll try and find it and post a photo tomorrow!

'73 LS-4 454 owned 21 3/4 years

Collecting n.o.s. parts for the resto for 21 of them!

[Joe L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Pictured below is what I believe to be a 3921975 air cleaner stud (1/4"-20-20 X 3.5", 1.25" & 0.60" thread lengths) as well as a NORS 3785256 stud which you "cut to fit". Both studs have a "blunt/pointed" top end. I buffed the 3.5" stud with my wire wheel to remove the very light surface rust.

Did the factory installed 3921975 air cleaner stud have a black oxide finish like the NORS stud?


Dave

Dave-----

The original GM #3921975 stud on my 1969 is black-phosphate finished.

[David L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Joe,

I have several original air cleaner studs (GM # 3942532) that were removed from Chevrolet V8's w/2bbl cars of the same era and they appear to have the black oxide finish. They are similar to the 3921975 stud EXCEPT they have a 0.40" diameter "stop" near the bottom end. The 3949532 stud measures 3.5" O.A.L. with 1.25" and 0.5" long thread lengths. The 3949532 will not fit in a Q-jet 4bbl. carb because of this 0.40" dia. "stop". If I had a lathe I could remove this 0.40" dia. "stop" and then extend the 0.5" thread length to 0.6" to essentially make a 3921975 stud.

Dave

[David L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

I rarely buy reproduction parts but after many years of looking for an original 3921975 air cleaner stud without any success I finally bought 3 of them from AMK Products. Last year I converted a Chev. 2-bbl stud (GM # 3942532) which also measured 3 1/2" long and were very common several years ago to a 3921975 stud. I believe that the AMK repro stud looks exactly like the originals. The 3921975 has more of a point on it on the top end than my conversion.

Dave

[Joe L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Dave-----


Here are some photos of an NOS GM #3921975 stud. By the label, this looks to be very old.


DSCN2813.jpgDSCN2814.jpg

[David L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Dave-----


Here are some photos of an NOS GM #3921975 stud. By the label, this looks to be very old.


[ATTACH=CONFIG]44338[/ATTACH][ATTACH=CONFIG]44339[/ATTACH]

Joe,

There is no question that your NOS 3921975 air cleaner stud is original GM. It does not seem to have much of a point on the top end. Don't you have a factory installed 3921975 stud on one of your cars? If so, does it have a "blunt" point or a "sharp" point?

Dave

[David L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Joe, Does the top end of your original 3921975 air cleaner stud look like the one in the photo below (70 Camaro SS350 stud & wing nut) that I hijacked from the NastyZ28 website. There was probably more than one vendor that made these air cleaner studs. Dave

[Joe L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Joe, Does the top end of your original 3921975 air cleaner stud look like the one in the photo below (70 Camaro SS350 stud & wing nut) that I hijacked from the NastyZ28 website. There was probably more than one vendor that made these air cleaner studs. Dave

Dave-----


Well, unfortunately, I can't find the original stud right now. Years ago, I removed the original stud from the carburetor and placed it in "the collection". That means it's in one of a bunch of parts group 3 tote bins and I don't know which one. I went through several of them in a somewhat cursory manner but I could not find it. I absolutely know it's in one of them, though.

My distinct recollection is that the top was configured just like the one you pictured. I know it was easy to get the wing nut started and without this sort of tip configuration it would not have been. It definitely does not have a "pointed", piloting tip.

Also, it definitely did not have a piloting tip on the bottom end. In fact, that's why I replaced it with a shortened GM #3785256. The non-piloting 3921975 was kind of difficult to thread into the carburetor and I did not want to grind a piloting tip on the original stud. So, I just used the easily available 3785256 and ground a piloting tip on the lower end and a "semi-piloting" tip on the top end

[David L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Joe,

I appreciate your efforts. I seem to always find specific parts when I am searching for other parts.

Dave

[Ron G.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Gentlemen, just so I am crystal clear on which carb application you folks are refering to. I am assuming the carb in question is a Quardrajet and not a Holley as I believe that stud is different in configuration and finish. Please correct me if I am wrong. Thank you.

[Joe L.]

Re: 1970 Corvette w/4bbl Q-jet air cleaner STUD

Gentlemen, just so I am crystal clear on which carb application you folks are refering to. I am assuming the carb in question is a Quardrajet and not a Holley as I believe that stud is different in configuration and finish. Please correct me if I am wrong. Thank you.

Ron-----


That's correct. The stud we are referring to here was used only on Q-Jets. The Holley carb stud was different (and different yet for L-88/ZL-1 and 3X2 engines).