70 350/350 Harmonic Balancer

[Bill L.]

I pulled the Harmonic Balancer. Where is the number on the balancer. The only numbers I can see are 7173 stamped on the outer face and K7F stamped on the small face as well.

What do these number indicate?

The rubber is clearly dry rotted and and has started to separate on the back.

Should I send it out to be rebuilt or buy a new replacement?

If I send it out, are there any recommendations?


Thanks!


Bill

[John H.]

Re: 70 350/350 Harmonic Balancer

Bill -

Google "Damper Dudes" and "Damper Doctor" for rebuild of dampers - both are located in Redding, California.

[Joe L.]

Re: 70 350/350 Harmonic Balancer

I pulled the Harmonic Balancer. Where is the number on the balancer. The only numbers I can see are 7173 stamped on the outer face and K7F stamped on the small face as well.

What do these number indicate?

The rubber is clearly dry rotted and and has started to separate on the back.

Should I send it out to be rebuilt or buy a new replacement?

If I send it out, are there any recommendations?


Thanks!


Bill

Bill-----


Generally, the 4 digit number stamped on the face of the balancer will be a derivative of the part number for the balancer. "7173" is a derivative (i.e. last 4 digits) of part number 3817173. However, that balancer is NOT correct for a 1970 L-46, although some versions of it are configured very much like the 1970 L-46 balancer. The 3817173 was used for 1962-68 SHP small blocks and was not used after 1968.

Check the location of the TDC groove on the balancer outer ring relative to the crankshaft keyway. If they line up, then the balancer you have is the 3817173 and it's not the right one for your application. If the TDC groove and crankshaft keyway do not line up (i.e. off by about 9 degrees), then you likely have the correct balancer and I do not understand why it has "7173" stamped on it.

[Bill L.]

Re: 70 350/350 Harmonic Balancer

Thanks Joe,

Well the groove and keyway are off set about 9 degrees as you suggest.

Cannot explain the 7173. I doubled checked to make sure and that is the number stamped in the balancer.

What number would be correct for L46? Does it really matter functionally or performance wise? The pulley makes seeing the number impossible once assembled.


Bill

[Joe L.]

Re: 70 350/350 Harmonic Balancer

Thanks Joe,

Well the groove and keyway are off set about 9 degrees as you suggest.

Cannot explain the 7173. I doubled checked to make sure and that is the number stamped in the balancer.

What number would be correct for L46? Does it really matter functionally or performance wise? The pulley makes seeing the number impossible once assembled.


Bill

Bill----


The number I would expect to see stamped on a 1969-1970 L-46 is "7712" which is a derivative of the part number, GM #3947712. However, based on your description of the timing mark position, I'm sure you have the correct balancer. I do not know why it's stamped the way it is.

The stamped-in numbers make no difference, at all, from a judging standpoint. As you mention, they cannot be seen and they are not judged.

By the way, just out of curiosity, your balancer does not have "fins" on the rear of the balancer hub section, does it? PRODUCTION versions of the 63-68 GM #3817173 balancer had the "fins" as did earlier SERVICE pieces. Later SERVICE pieces did not have the "fins".

As far as I know, no examples, PRODUCTION or SERVICE of the 3947712 ever had the "fins". However, since I'm virtually certain that yours is a GM #3947712 due to the configuration, timing mark location and the strong liklihood that it's original to the car, if it has the "fins", then I suppose that tells us that I'm mistaken about early versions of the 3947712 not having "fins".

[Bill L.]

Re: 70 350/350 Harmonic Balancer

Thank you for all the help Joe.

There are no fins on the back.

I do know I had no trouble timing the motor and there were a great number of original components in the engine compartment. Based on your input I am fairly confident it is the original. The engine and engine compartment were fairly original with the exception of the headers.

I think the best course is to keep what I had since it worked well, and send it out to be rebuilt.

Does anyone have first hand experience with Damper Dudes or Damper doctor as noted in earlier response?


Bill

[Timothy B.]

Re: 70 350/350 Harmonic Balancer

I have a harmonic balancer I always thought was 69-71 350 HP but it has 7704H stamped into it. My parts book says 69-71 corvette 350 exc. high performance and special high perf. This balancer is 8" diameter and 1 5/16" thick, no fins. Did low performance use a 8" balancer?

[Joe L.]

Re: 70 350/350 Harmonic Balancer

I have a harmonic balancer I always thought was 69-71 350 HP but it has 7704H stamped into it. My parts book says 69-71 corvette 350 exc. high performance and special high perf. This balancer is 8" diameter and 1 5/16" thick, no fins. Did low performance use a 8" balancer?

Tim----


Yes, 1969-71 Corvettes with base engine used the balancer you mentioned. It's an 8" balancer that's 1-5/16" thick. Many folks THINK that all Corvette base engine small blocks used a 6" balancer. That's WRONG. Most did but NOT 69-71.

The 69-70 L-46 used the same balancer as 70-72 LT-1. It's also 8" but thicker than the base engine unit.

[Pat M.]

Re: 70 350/350 Harmonic Balancer

My base 70 has this very same 8", 1-5/16" balancer and it could very well be original to the car. And Joe's right (what a shock ) - it's amazing how many people recently told me that's the wrong balancer for my car.

[Pat M.]

Re: 70 350/350 Harmonic Balancer

Does anyone have first hand experience with Damper Dudes or Damper doctor as noted in earlier response?
Bill

Bill - I just got my damper back from Damper Doctor and I'm very satisfied.
Great communication, lightning fast turnaround (1-2 days, excluding shipping time), super reasonable price ($42, excluding shipping), and the work appears to be excellent.