Harmonic balancer

[Kelly Burnside]

I have a question on a harmonic balancer on my 1969 corvette. The car is an 350/300 with an automatic transmission (original engine). The NCRS manual states that I should have a harmonic balancer that is 6" by 1 1/4 inches. My Harmonic balancer is 8" by 1 5/16". Part number (?) 6966 on the harmonic balancer. Possibly corresponding to GM part number 2896966. There is a stamped number of 7704H on the front. The timing cover tab is the correct one as seen in the NCRS manual and it lines up with the harmonic balancer.
Question: is this the original harmonic damper? Should I have the 6" one on the car as stated in the NCRS book. I believe that the timing cover has never been removed but can't garauntee that has not been replaced. So logic would think that if the harmonic balancer was supposed to be the 6" type then the tab would have to be moved inward to accomodate the extra inch that the timing tab needs to be placed in order to get proper alignment.
Thanks for any help on this question.

[Joe L.]

Re: Harmonic balancer

Kelley-----

Your engine has the correct balancer. ALL 1969-71 Corvettes with base engine (300hp-69-70; 270hp-71) used an 8" OD balancer which is 1-5/16" thick. The original part number was GM #3947704 (which is where the derivative "7704" originates). Later, this piece was discontinued and superceded by GM #6272222 which remains available and is identical to the original piece in all aspects of configuration except the stamped numbers (which cannot be seen when installed on the car).

I think that you may be looking at an earlier edition of the judging manual which did indicate that the 6-3/4" balancer was correct for 1969 with 300 hp. I think that the latest edition of the 1968-69 JG made the correction. If not, then it's still in error. NO 1969-71 small block Corvette used anything but an 8" balancer (although thickness varied for base engine and 350/370 hp editions)

[Kelly Burnside]

Re: Harmonic balancer

Thanks Joe.. appreciate the help.. Is there by chance a GM parts number manual that is available that lists all of the GM part numbers? Interesting enough, Rick Bizzoco book on the 1969 stingray does not mention anything on the harmoinic balancer... also the 1969 assembly manual has nothing on the harmonic balancer. The NCRS manual I bought from a NCRS judge who had it as a spare (Summer 2001 Third Edition) Godd source of information. But is there a good technical book for(ALL OF)the GM part numbers?
Thanks again for your help.

[Joe L.]

Re: Harmonic balancer

Kelly------

There's no "one source" for the info you seek. A 1969 edition of the Corvette Parts and Accessories Catalog is about as good as you can get(but hard to find).

[Kelly Burnside]

Re: Harmonic balancer

Ok thanks..Doubt if I will ever find that book... Thanks for the help.