63 to 65 fuel filter brackets for hi HP

[John D.]

More trivia for you. Most of us are aware of the fact that the 63 to 65 fuel filter bracket is held onto the base plate or intake with an adapter stud, washer, and thin hex nut. I am speaking of the hi-hp cars.
Over the last 1/4 century or more a lot of us think that under the jam nut is an outside star washer. So you have the adapter stud, the bracket, the washer and then the nut. But in reality the C2's had a flat washer-plain steel one at that. They did NOT have the outside star washer we are so accustomed to seeing in catalogs and on the cars.
I believe that the idea of the outside star washer derived from the 57-58 FI fuel filter bracket. Now those cars did in fact use the star washer. Or I am told that they did.
Greg if you are looking in we would appreciate you posting a photo of your original fuel filter bracket set-up showing this flat washer.
By the way this is the same flat washer that is used on the left hand exhaust manifold adapter stud that holds on the clean air tube. Look in the aims for this washer number. Look in your old GM parts books and look in the Standard parts books for all the number.
Now what I would like to have is the GM part number for the adapter stud. Can't seem to find it. This stud was a circle on the top on it. Stamped in. Some call it an "O" but it's perfectly round and very deep. Same configuration as the 57-58 FI cars. Thanks, John

[Gregory G.]

Re: 63 to 65 fuel filter brackets for hi HP

John,

My 45,000 mile April 7 1964 car has the flat washer you described on the fuel filter bracket stud.I will gladly post a photo later on to help us all in this area.
At our Chapter Meets the 400+ point Judges agreed it should be a flat washer not a Star washer. Other 63 & 64 owners what is installed on your cars?

Greg

[John D.]

Re: 63 to 65 fuel filter brackets for hi HP

Greg, You can't believe the guys that are writing me telling me that there cars have or had the flat washer instead of the outside star. I like these little hardware details. Thanks for your imput. Look forward to seeing a photo. John D.

[Joe L.]

Re: 63 to 65 fuel filter brackets for hi HP

John-----

A flat washer is what they were supposed to have. GM #120394. It had an OD of 13/16", a hole size of 13/32" and was 1/16" thick. It was zinc plated.

You can still get these from GM under the original part number. They are supplied in a package of 10, so your dealer will want you to purchase the whole package. However, I'll bet you can get a washer very similar, or even identical, in a hardware store.

[John D.]

Re: 63 to 65 fuel filter brackets for hi HP

HI Joe, Thanks for backing me up on this part. Your information is 100% correct. Is it OK for me to quote your answer on a little article I am writing when I get caught up some?
Can you provide the part number of the adapter stud for the filter bracket? I was hoping that you could find it in your huge collection of parts books. I am trying to find out if this adapter stud (don't know correct name) was the same one as the 57-57 FI cars. It appears to be from the same company but I don't know about the length, etc. Thanks, John

[Timothy B.]

Re: 63 to 65 fuel filter brackets for hi HP

Picture of exhaust manifold stud for clean air tube showing flat washer and thin nut. This is NOT off a Corvette but a early 63 Impala SS Flint built 327/300 October 1962. There are still remains of the frenck lock but our books say it was not used on the middle exhaust manifold bolts.

[Robert Jorjorian]

Re: 63 to 65 fuel filter brackets for hi HP

Good chance what looks like remains of french lock is actually a piece of the lower choke tube attaching bracket. might have rusted off or was broken off when someone tried turning the jam nut to loosen it and the entire bolt turned breaking off the tube brkt.

[Joe L.]

Re: 63 to 65 fuel filter brackets for hi HP

John-----

Although I'm not 100% sure about it, I believe the stud used for 1957 with FI was GM #3726578 or 3721702. These studs are very close to being the same and, functionally, are the same. I don't know if the finish differs on them. The GM #3726578 was discontinued on March 1, 1961 and replaced by the 3721702. However, both studs were around well before 1957 and they could have been used interchangeably.

For 63-65 applications, I think that the stud likely used was the GM #3731702. Once again, I'm not 100% sure about this. The GM #3731702 was discontinued without supercession in January, 1999.

As far as manufacturer's markings go, I would not be surprised if that changed over the long period of this part's use and availability. So, the markings on the end could vary. I have some of the 3731702 around here but they're a group 3 part and I have a LOT of tote bins full of group 3 parts and I don't know which one they're in.

By the way, the nut used for the filter bracket fastening was GM #124829. This is a 3/8-16 JAMB nut (thin--7/32"), SAE grade 5 and it's zinc plated. It's still available from GM for about $3.50 EACH, or I'll bet a good hardware store would have an identical nut.

[Joe L.]

Re: 63 to 65 fuel filter brackets for hi HP

Tim-----

There's no possible way that the french locks used on the end bolts could be used for the center bolts----there's no just no way that they would fit. For a french lock to EVER have been used on the center bolts, it would have to have been a completely different design and configuration. Such a french lock was, as far as I know, "never invented" by GM for use on any small block engine.

[John D.]

Re: 63 to 65 fuel filter brackets for hi HP

Joe, Thanks very much for all your information and hardwork on this subject. We certainly appreciate it.
The 120394 part-the thin washer that is repackaged by GM parts is a replacement washer. Pretty close though. But the originals were a tad thinner and just plain steel. I would think that the zincad ones would be the ideal choice to use but not original.
Wow 3.50 for a jam nut that is readily available in industrial tool stupply houses for peanuts. Course you have to buy a 100.
I believe the adapter stud was black phosphate in 57-58 and maybe 63 to 65 also. The repros we see are shiney. On the other hand as you know there was not just one finish for this hardware. On the FI's there were many options speced on the prints. Split lockwashers alone with spec'ed cad, zinc, black, plain. Course convincing people of this is not easy. Take care, John

[Robert Jorjorian]

Re: 63 to 65 fuel filter brackets for hi HP

John,never found a jam nut that matched GM's jam nut in exact dimensions from hardware stores.
Maybe some have them but without a GM nut to use as a reference point its unlikely you'll be that lucky. All depends if your motive is restore a car exact or just add parts that somewhat resemble the real deal.

[John D.]

Re: 63 to 65 fuel filter brackets for hi HP

Dear Robert, What kind of mic do you have. Are u using .0000 mic or a chepp .000 mic??? I suspect the latter (ladder). Is this the ladder u use for long walks w/Indy??? Anyhow I have found the EXACT nut but not from hardware store. Found it from massage parts collection over last 40 years in dry climate. Luckily I don't live in the swamp where u do Robert. By the way sir is that the name u usually go by??? Are u the mrgmpartsmen on ebay??? Was wondering who many of the FI rubber diaphragms you have as for last 5 maybe 10 years now see them for 19.95. Noticed you raised the price. Anyhow I do have an exact nute-rh thread for the correct adapter stud for the fuel filter. Also have the correct THIN 3/8" SAE washers. Not fake ones. Thanks for your informative letter. Jr.

[Joe L.]

Re: 63 to 65 fuel filter brackets for hi HP

John-----

The washer currently available under GM #120394 may very well be different in some ways than the original. I don't have any of the latter day washers, and I've never compared them to originals. However, the GM spec for the part says that it was to be zinc plated and that it's to be 1/16" thick. How thick are the current ones and how do they otherwise compare dimensionally to the specs I previously provided?

Another thing: a washer like the 120394 was once used by the tens of millions. So, I would strongly suspect that GM had multiple suppliers. How do we know that every one, even used in a given model year, were all precisely and exactly the same? Any of the dimensions have an allowable (+) or (-) tolerance, so slight variations may be well within specs.

[John D.]

Re: 63 to 65 fuel filter brackets for hi HP

Joe, My second attempt to answer you. Pushed the wrong button. Anyhow one of the earlier Standard Parts Books lists this washer and its finish. Hanson emailed me a page from this book. Thickness of the washer is listed at about .0550 which as I said is a tad thinner than the 1/16 which is .-625 thickness which you found. The ones in the new GM bags are 1/16 and thicker. Since the top of the adapter stud is so short there is not much room for a thicker washer. Thin nut barely fits now. The plating of the original washer is listed as bare steel-not zincad. As Jorjorian said in the photo he sent us the thin hex nut is another issue as the original GM one is quite a bit thinner than today's typical "jam" nuts. The thin nuts was zincad. The adapter stud should be blackened. The adapter stud should have a nice big circle stamped in it quite heavily. Rare part. A carry over from the 57 era except the dimensions are not quite the same. That's it for me on this project. Now to convince the world that many thousands of midyears-hundreds anyhow- need a flat washer for the fuel filter brk instead of a star washer on the HHP cars. Once again it's the same washer as used on the 63-65 clean air tube brkt to the exhaust manifold. John

[Joe L.]

Re: 63 to 65 fuel filter brackets for hi HP

John-----

The GM spec that I have for the GM #120394 washer has it as being zinc plated. All the washers in the 1203XX series are zinc plated. Maybe the spec changed over the years. Also, the dimensional specs that I have are FRACTIONAL sizes. Often, these are used in parts information since the decimal specification has a significant tolerance (i.e. 1/16" thickness equals a range of, perhaps, .050" to .070").

Anyway, the GM spec for the washer is 13/32" ID, 13/16" OD and 1/16" thickness.

I purchased a package of SAE washers in a hardware store this morning. There were 20 in the bag. They are supposed to be 1/16" thick. I measured them. The thinnest was about 0.055" and the thickest about .072". As far as ID go, they are right at 0.415" and as far as OD goes, they are at 0.815". These dimensions fall almost exactly at the GM spec for ID and OD of the 120394 and I'm sure well within GM's allowable tolerance for the part. These are also zinc plated. However, if one doesn't like the plating, about 10 seconds in a solution of muriatic acid and you'll have a nice bare steel finish.

I also picked up a jamb nut. This one is 3/8-16 thread size, 7/32" thick, and zinc plated. All of those characteristics match what GM calls out for the GM #124829 nut. This is a "finished" style jamb nut with the tapering at the points. I don't know if the 124829 was a "finished" style nut or a "non-finished" style which has no tapering at the points. Those are the only 2 styles that I know of; there may be others, though.

A photos is attached below.