1967 L79 HT Harmonic Balancer
For a very early 1967 car 327/350hp with manual transmission and no power steering, what is the correct original harmonic balancer part number and are they still available from GM under a different number? Does anyone have a photo inside and out of an original? including mounting bolt/washer? Thanks
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Dino Lanno -
Re: 1967 L79 HT Harmonic Balancer
Dino-----
The part number was always GM #3817173. It's still available under that part number for about 125 bucks, GM list. However, the current part, although of the original part number, is not configured like the original piece. For one thing, it lacks the "fins" on the rear of the hub section. For another, the face of the hub is configured differently. It's 100% functional, though, and, installed in the car, is not easily discerned from original (but it is discernable by someone that's in-the-know and looking for it).In Appreciation of John Hinckley -
Re: 1967 L79 HT Harmonic Balancer
Thanks Joe...thats exactly the information I needed....I appreciate it...
Do you happen to know off hand what the washer bolt configuration for the balancer on an early 67 was? headmarkings?Dino LannoComment
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Re: 1967 L79 HT Harmonic Balancer
Dino-----
The bolt was a special bolt. The head had 6 lines (i.e. SAE grade 8) and was of trimmed configuration (i.e. NON "indented" head). I believe that "TR" was one common headmarking but there were likely others. Some, if not all, of the bolts were zinc plated and had a hole for safety wire.
The lockwasher was a HD split lockwasher.
The large flat washer was plain steel; no plating, at all.In Appreciation of John HinckleyComment
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Re: 1967 L79 HT Harmonic Balancer
Dino,
The finned harmonic balancer is available from Paragon but I paid about $300.00 for mine.
Might be more now as I bought mine 2 years ago.
Zip Products might also have it
KurtComment
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Re: 1967 L79 HT Harmonic Balancer
Went to my stash and found a grade 8, M mark split lock washer and thick washer.....check these photos....
I should note that the bolt does not have a safety wire hole through it...
Joe your knowledge on this stuff is amazing.....Last edited by Dino L.; November 24, 2008, 08:23 PM.Dino LannoComment
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Re: 1967 L79 HT Harmonic Balancer
Dino,
My late build 67 L-79 bolt did not have a hole for a safety wire. I should note that many parts on my car have been determined to be original but not all have been correct.
RickComment
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Re: 1967 L79 HT Harmonic Balancer
Dino-----
That looks like the one, alright. The "M" headmarking (i.e. Michigan Screw Products) was a major supplier to GM during the period.
As far as the safety wire hole goes, I don't know what the deal is. I've seen the bolt with and without the hole. The bolt is still available under the original part number of GM #3815933. The current bolts all have the holes.
However, keep one other thing in mind: the GM #3815933 bolt was used for all 1962-68 small blocks which used a crankshaft snout bolt. For 1969-82 , though, during which period all Corvette small blocks used the snout bolt, the bolt changed. For 1969-82 the bolt was GM #9428643.
So, how did the 9428643 bolt differ from the 3815933 used earlier? Well, it was the same 2-1/4" overall length, the same 7/16-20 thread size and the same GM 300M material grade, but it had 1-1/8" of thread length compared to 1" of thread length for the 3815933. Also, it had a phosphate finish and definitely had NO safety wire hole in the head. It was used in conjunction with the same lock washer and same large, thick flat washer as used for 62-68 applications. So, it's possible that's what you have, unless you know that what you have originated from a 62-68 SHP application. Even then, I would not rule out that the GM #9428643 was used by the factory during the 62-68 period as a substitute for the 3815933 and that may explain why some of the 62-68 bolts are found without safety wire hole and with phosphate finish. There's no reason why the factory could not have used it; it was in the GM "parts bin" of the period.
Another curiosity: from 1962-64 , the lock washer specified for use with the bolt was GM #131718. This is a SPLIT LOCK WASHER. From 1965-82, the lock washer specified was GM #138494. This is an EXTERNAL TOOTH STAR WASHER. However, the AIM's through 1972 depict a split lock washer (although this depiction might be an anachronism). Also, my original owner 1969 small block was originally built with a split lock washer. Other earlier small blocks that I've observed have used split lock washers, too, although I couldn't say that all did. But, I think that the GM #131718 was actually used in PRODUCTION for a lot longer than just through 1964.In Appreciation of John HinckleyComment
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