'70 LT1 w/AIR bracket stud

[Donn M.]

My early '70 LT1 w/AIR has a silver alternator/AIR mounting stud on the water pump. The TIM states on page 152 that engines w/AIR "..have a black plated stud .." to secure the alternator adjusting brace and refers to pics. 12.19 and 12.21 where the stud appears silver. I am unable to find a black plated stud anywhere and my silver one has never been pointed out by judges at past events.
Am I reading this wrong? Looking for verification before having mine plated.
Thanks for any confirmation.

[Joe L.]

Re: '70 LT1 w/AIR bracket stud

My early '70 LT1 w/AIR has a silver alternator/AIR mounting stud on the water pump. The TIM states on page 152 that engines w/AIR "..have a black plated stud .." to secure the alternator adjusting brace and refers to pics. 12.19 and 12.21 where the stud appears silver. I am unable to find a black plated stud anywhere and my silver one has never been pointed out by judges at past events.
Am I reading this wrong? Looking for verification before having mine plated.
Thanks for any confirmation.

Donn------


The original stud, GM #3877646, was black phosphate finished. That stud was discontinued from SERVICE in April, 1976 and replaced by GM #3927111. The latter was discontinued in July, 1979 and replaced by GM #461318 which was discontinued without supersession some time ago.

I do not know what the finish was on the 3927111 but the 461318 was zinc plated.

One thought: although it replaced the 3877646 in 1976, the 3927111 was originally released way back in 1968. It is possible that it was used in PRODUCTION alternately with or as as a substitute for the 3877646 and it's possible that it was zinc plated. Just a theory, though.

[Donn M.]

Re: '70 LT1 w/AIR bracket stud

Joe ,
Thanks for the detailed info. and theory. Motor was rebuilt really well before my ownership except for some small details. Water pump not dated and incorrect bolts. Obtained a correct dated pump and bolts. For now will use zinc stud and put it on my dark phosphate list to replate when I accumulate a few more items.
Made a copy of your response for my file, as I have on many of yours to others in the past.
Thanks again, Donn

[Joe L.]

Re: '70 LT1 w/AIR bracket stud

Joe ,
Thanks for the detailed info. and theory. Motor was rebuilt really well before my ownership except for some small details. Water pump not dated and incorrect bolts. Obtained a correct dated pump and bolts. For now will use zinc stud and put it on my dark phosphate list to replate when I accumulate a few more items.
Made a copy of your response for my file, as I have on many of yours to others in the past.
Thanks again, Donn

Donn------


One more thing I should have mentioned: the original stud used in PRODUCTION was supposed to be GM #3889313. However, that stud was never available in SERVICE. From the very beginning, the stud available in SERVICE for the application was the GM #3877646. How they differ I do not know. However, I know that the 3889313 was black phosphate finished because the same stud was used on my 1969 350/300.

My theory about substitute PRODUCTION studs still holds, though, but now I would say there were 3 possibilities: the 3877646, the 3889313, and the 3927111.

[Gary B.]

Re: '70 LT1 w/AIR bracket stud

I looked at my July built 70LT1. It looks zinc-plated. I rebuilt the water pump last spring. When I removed the bolts, the paint was chipped off.
I'll look at Terry's tomorrow, it's a January built LT-1. Might be a early vs late.
Food for thought... the stud was installed before the engine was painted, to hold the water pump on. It should have orange paint on it. Putting on the outer nut and lock-washer may have chipped the paint off the end, but not the hex. Paint it orange, nobody will know the difference.
Gary B

[Joe L.]

Re: '70 LT1 w/AIR bracket stud

I looked at my July built 70LT1. It looks zinc-plated. I rebuilt the water pump last spring. When I removed the bolts, the paint was chipped off.
I'll look at Terry's tomorrow, it's a January built LT-1. Might be a early vs late.
Food for thought... the stud was installed before the engine was painted, to hold the water pump on. It should have orange paint on it. Putting on the outer nut and lock-washer may have chipped the paint off the end, but not the hex. Paint it orange, nobody will know the difference.
Gary B

[Donn M.]

Re: '70 LT1 w/AIR bracket stud

Hey Gary,

Appreciate your response.
Mine is a mid March build. If Terry's is zinc then Joe's thought of mixed installation could be pretty accurate.
I'm curious but don't go to a lot of trouble. I've got the correct "TR" bolts painted and am going to use the zinc stud when I install pump. It will be a few days as I have hand surgery Thursday.
Thanks, Donn

[Donn M.]

Re: '70 LT1 w/AIR bracket stud

Hey Joe,

Thanks for the additional details.

Donn

[Gary B.]

Re: '70 LT1 w/AIR bracket stud

Donn, I hope we are talking about the right stud, or should I say the left stud. I went to my other building and looked at Terry's end-of-January built 70 LT-1. The stud looks like my 70, and also looks like a Zinc-plated stud. See Picture below.

2023-03-29 10.36.32.1.jpg

Joe. Being an early 70, and 69 production running longer, I thought Tery's 70 might be different. Looking at 1969 AIM UPC 6, Sht. A2, Item #9 shows the stud being 3889313.
1970 AIM UPC LT1, Sht. A3 also shows the same number, Item #5, 3889313. The 71 and 72 AIM show the same part number. No change records are indicated through 72 AIM.
Can you tell me what the finish of that stud is?
Appreciate the help, just trying to make the manual right.
Gary B

[Joe L.]

Re: '70 LT1 w/AIR bracket stud

Donn, I hope we are talking about the right stud, or should I say the left stud. I went to my other building and looked at Terry's end-of-January built 70 LT-1. The stud looks like my 70, and also looks like a Zinc-plated stud. See Picture below.

[ATTACH=CONFIG]116217[/ATTACH]

Joe. Being an early 70, and 69 production running longer, I thought Tery's 70 might be different. Looking at 1969 AIM UPC 6, Sht. A2, Item #9 shows the stud being 3889313.
1970 AIM UPC LT1, Sht. A3 also shows the same number, Item #5, 3889313. The 71 and 72 AIM show the same part number. No change records are indicated through 72 AIM.
Can you tell me what the finish of that stud is?
Appreciate the help, just trying to make the manual right.
Gary B

Gary------


The stud in the photo is unquestionably zinc plated. However, what the part number is of that stud is in question.

Below find a photo of an NOS GM #3877646. This is the stud once available as the SERVICE stud for small blocks with AIR and the PRODUCTION/SERVICE stud for big blocks with AIR. You will note that it's black phosphate or black oxide finished.The PRODUCTION stud for small blocks was GM #3889313 which, as I mentioned, was never available in SERVICE.

I believe that the 3889313 was definitely used for 1966-67 small blocks with K-19. That's because the follow-on stud, GM #3927111, was not released until 1968. However, from 1968 onward I think the 3927111 was used at least on some cars or, even, exclusively. I suspect the 3927111 was zinc plated.

Generally speaking, I have found that studs like these of the 38xxxxx part numbers are black finish. So, I suspect that the 3889313 was black finished and I know that the 3877646 was black finished.

What would be VERY interesting would be to see the studs installed on KNOWN-ORIGINAL 1966-67 small blocks with K-19. If these are black finished, then we know the 3889313 was black finished and it was not the stud used for 1968+ with AIR and zinc plated studs.

DSCN4161.jpgDSCN4162.jpg

[Gary B.]

Re: '70 LT1 w/AIR bracket stud

Thank you Joe.
Gb

[Donn M.]

Re: '70 LT1 w/AIR bracket stud

Joe and Gary,

Geez guys, you really got into this. Thanks for all the effort. Sounds like either one would be acceptable.
Thanks for everything. You both are GREAT!!
Donn