harmonic balancer

[Bill B.]

Re: harmonic balancer

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[Bill B.]

Re: harmonic balancer

I totally screwed up the above post #16 as far as any text so I'll put it here. This is the 3896904 balancer I received today. I ordered it from a Chevy dealer in my area. I'm posting the pics mainly so Joe Lucia can confirm this is the correct balancer for aa 65, 300 hp. The box seems to confirm it came from a GM Service Parts Operation. Any confirmation would be great for me as well as anyone needing a correct balancer. It can still be ordered through a dealer and I paid $112.

[David L.]

Re: harmonic balancer

Bill,
The 3896904 balancer (stamped "6904") did not exist in 1965. As per Chevrolet Parts History for service parts GM # 3817684 was replaced in 11/64 by GM # 3861968 which was then replaced in 11/65 by GM # 3861970 which was then replaced in 11/65 by GM # 3861970 which was then replaced in 6/71 by GM # 3896904.
I have several 62-65 balancers and they are the "stepped type" (6.1" to 4.5"). Attached is a copy of my research done back in the 1990's.
Dave

[David L.]

Re: harmonic balancer

Attached is a photo of an original 1966 Chevrolet (w/327) 6" balancer that is stamped "E6F" where the "E6" = May 1966. All the other components on the engine were dated in May 1966.
Dave

[Joe L.]

Re: harmonic balancer

I totally screwed up the above post #16 as far as any text so I'll put it here. This is the 3896904 balancer I received today. I ordered it from a Chevy dealer in my area. I'm posting the pics mainly so Joe Lucia can confirm this is the correct balancer for aa 65, 300 hp. The box seems to confirm it came from a GM Service Parts Operation. Any confirmation would be great for me as well as anyone needing a correct balancer. It can still be ordered through a dealer and I paid $112.

Bill------


Your car likely was originally fitted with the GM #3861968 balancer that Dave mentions in his posts. I don't know the configuration of this balancer as I've never seen an NOS example to confirm part number with configuration. There were several supersessive balancers used over the 1963-67 period and it's possible that some were used interchangeably for some period of time on the assembly line, especially in the 1965-66 period. It is true, though, that your car could not have been originally fitted with the GM #3896904 balancer as it did not yet exist in 1965. As Dave mentioned, the 3861968 was discontinued in November, 1965 and replaced by the GM #3861970 with the latter discontinued and replaced by the GM #3896904 in July, 1971.

The GM #3896904 is, thus, not NCRS-correct for a 1965 with L-75. However, the GM #3896904 is the last available GM replacement for your application and, thus, is functionally correct. I would use it without reservation. In fact, personally, I would prefer it over the earlier designs. GM did not develop and SERVICE the 3896904 for 50 years because the earlier, short-lived designs worked just as well. Also, I prefer a NEW balancer over any rebuilt or used balancer any day of the week and twice on Sunday.

By the way, 1966 Corvettes with 300 HP originally were equipped with balancer GM #3883204. This balancer was discontinued from SERVICE in July, 1966 and replaced by the 1967 300 HP balancer, GM #3896903 . The GM #3883204, 3896903, and 3896904 were absolutely identical in configuration. These was some difference in "tuning" between them but I do not know how it was accomplished. It definitely did not involve a difference in apparent configuration (except that the 3896903 MAY have been stamped "6903" and the 3896904 MAY have been stamped "6904".

The balancer you obtained is obviously a GM-sourced part. I remain surprised that your dealer was able to obtain it out of a GM warehouse as I show it as GM discontinued without supersession. Usually, when the GM "discontinued" is issued, it means that all existing warehouse stock is exhausted.

[David L.]

Re: harmonic balancer

Joe,
Attached is a photo of the side view of my original 1966 Chevrolet 327 balancer stamped "E 6 F" (May 1966) from the complete engine that I bought from a salvage yard in Orange, MA for $25 back in the 1980's. All the components (engine block, heads, intake, carb, starter, and fuel pump had date codes in May of 1966. I believe that the balancer is GM part # 3883204 since my 1966 Chevrolet Parts Catalog (Oct. 1966) lists GM # 3883204 in Gr. 0.659 for the following: 66 ALL, CORVETTE w/forged crankshaft (327)(exc. Sp. H/Per.). Note that part of the balancer has a rough cast as opposed to being machined. The back side had the casting numbers as follows:
"388"
"3 _ _ 5"
where the hole eliminated 2 digits, probably "20"
I assume the complete casting number was "3883205" as casting numbers differ from part numbers by a digit or two.

GM # 3883204 was replaced in 7/66 by GM # 3896903.
Dave

[John F.]

Re: harmonic balancer

I think this is what you are looking for. It was on my 1965, 365hp/327ci. I am hanging on to it. The prior owner did not like the 30-30 cam and replaced it when changing to hydraulic cam. It is 8" diameter and has the fins.