Harmonic Balancer Code question(s)

[Keith M.]

Well...pulled the balancer off my Oct 69 L46 4spd and of course it is not original/correct. It is stamped as follows Casting #3942538 on back; on the front is 7712 (presumably last 4 of p/n) and G 9 F which would be July 1969. (Adding...7712 is for an LT1...given the 1969 strike and other possible part challenges...could this 7712 balancer been born with my car? Having asked that...the back of it is fully painted orange...which would not be original....AND my intake and both exhaust manifolds were not what the car was born with.)

AFAIK I need p/n 6272224. Here is where it gets a little tricky. I have a line on a 2224 which has that stamped on the front but also on the front is A45S. Not sure how to interpret that last code???? Jan 1974? 1975?

[Joe L.]

Re: Harmonic Balancer Code question(s)

Well...pulled the balancer off my Oct 69 L46 4spd and of course it is not original/correct. It is stamped as follows Casting #3942538 on back; on the front is 7712 (presumably last 4 of p/n) and G 9 F which would be July 1969. (Adding...7712 is for an LT1...given the 1969 strike and other possible part challenges...could this 7712 balancer been born with my car? Having asked that...the back of it is fully painted orange...which would not be original....AND my intake and both exhaust manifolds were not what the car was born with.)

AFAIK I need p/n 6272224. Here is where it gets a little tricky. I have a line on a 2224 which has that stamped on the front but also on the front is A45S. Not sure how to interpret that last code???? Jan 1974? 1975?

Keith-----

The original balancer for your application was GM #3947712. That balancer was used for 1969-70 L-46 as well as 1970-71 LT-1. The GM #6272224 was first used for 1972 LT-1 and became SERVICE for the referenced 1969-71 applications when the 3947712 was discontinued in July, 1972.

Except for the various stamped codings, the 3947712 and 6272224 are identical with respect to configuration and cannot be told apart.

[Keith M.]

Re: Harmonic Balancer Code question(s)

Keith-----

The original balancer for your application was GM #3947712. That balancer was used for 1969-70 L-46 as well as 1970-71 LT-1. The GM #6272224 was first used for 1972 LT-1 and became SERVICE for the referenced 1969-71 applications when the 3947712 was discontinued in July, 1972.

Except for the various stamped codings, the 3947712 and 6272224 are identical with respect to configuration and cannot be told apart.

Well that is some happy news. Makes sense as when I pulled mine off I really had the sense it was original in part because of the date stamp. I want/hope to preserve original parts wherever possible. Off to Damper Doctor it shall go and one less replacement part to hunt.

I am curious what is your source of this information for my future reference. I ask because I could not find much anywhere. AIM has nothing as engine including balancer came to the line assembled. TIM&JG had nothing for part nums. I did check the Parts Catalog which is where I got the 2224 info...not remembering at the time that said catalog is dated Dec 1983 and so only shows the then current service replacement part #'s without predecessor info. Lastly, google searches revealed information of dubious validity.
Thank you!

[Keith M.]

Re: Harmonic Balancer Code question(s)

Here are some pics of the balancer. Intend to send to Damper Doctor for rebuild. He says he paints it all black. That's fine cux I can just spray the front Chevy Orange when I repaint the engine. A question I have is....should I blast it before I send it out?? Reason I ask is...am doubting they will strip the paint but more likely just prime...if that...and paint it all black. Would it be better to blast it down to metal first just to be safe?

[Donn M.]

Re: Harmonic Balancer Code question(s)

Hey Keith, I just got mine back from the Damper Doctor and had him leave it unpainted. Wanted to be sure it was primed myself and the right
Chevy orange and heat resistant.. To answer your question, it was completely stripped bare metal. Appears to be a really nice job.
Good Luck, Donn

[Keith M.]

Re: Harmonic Balancer Code question(s)

Hey Keith, I just got mine back from the Damper Doctor and had him leave it unpainted. Wanted to be sure it was primed myself and the right
Chevy orange and heat resistant.. To answer your question, it was completely stripped bare metal. Appears to be a really nice job.
Good Luck, Donn

So you sent it with legacy paint and they returned it stripped bare metal??

[Donn M.]

Re: Harmonic Balancer Code question(s)

It was painted orange on both sides when I sent it to him, so I assume that the painting was done when previous owner had the motor rebuilt. Yes, it was bare metal upon return. I don' know his process for stripping, I just wiped with lacquer thinner and primed.
He received it Friday about 4 pm and called me Monday morning to tell me it was done. Fantastic service.
Here's the rest of the story; We originally removed it to replace the crank front seal. The damper separated into 2 pcs. in our hands. It had worn a groove about 3 quarters of the way through the timing chain cover. It appears the LT1 front pulley is a bit larger in diameter than the dampers interior diameter which kept it from coming off. So correct rebuilt damper, new dated water pump, new correct timing cover and oh, better not forget the front seal.

[Joe L.]

Re: Harmonic Balancer Code question(s)

Well that is some happy news. Makes sense as when I pulled mine off I really had the sense it was original in part because of the date stamp. I want/hope to preserve original parts wherever possible. Off to Damper Doctor it shall go and one less replacement part to hunt.

I am curious what is your source of this information for my future reference. I ask because I could not find much anywhere. AIM has nothing as engine including balancer came to the line assembled. TIM&JG had nothing for part nums. I did check the Parts Catalog which is where I got the 2224 info...not remembering at the time that said catalog is dated Dec 1983 and so only shows the then current service replacement part #'s without predecessor info. Lastly, google searches revealed information of dubious validity.
Thank you!

Keith------

For the most part, my source of information on your question was my own, personal knowledge. The only thing I had to look up was the date of discontinuation of the 3947712 balancer.

In general, information on questions like yours can be found in old editions of the P&A catalogs or other references which are difficult, if not impossible, for most to obtain.

By the way, the 3942538 seen on the hub section of the balancer you pictured is the casting number for the hub section and is not the part number of a finished balancer assembly.

[Keith M.]

Re: Harmonic Balancer Code question(s)

It was painted orange on both sides when I sent it to him, so I assume that the painting was done when previous owner had the motor rebuilt. Yes, it was bare metal upon return. I don' know his process for stripping, I just wiped with lacquer thinner and primed.
He received it Friday about 4 pm and called me Monday morning to tell me it was done. Fantastic service.
Here's the rest of the story; We originally removed it to replace the crank front seal. The damper separated into 2 pcs. in our hands. It had worn a groove about 3 quarters of the way through the timing chain cover. It appears the LT1 front pulley is a bit larger in diameter than the dampers interior diameter which kept it from coming off. So correct rebuilt damper, new dated water pump, new correct timing cover and oh, better not forget the front seal.

Donn,
Very helpful...thank you. But of course the restoration rabbit holes continue!

Firstly, your post got me thinking....being as the engine was painted after the balancer was installed...what are the implications for finishing this area? Meaning...how should the back of the balancer be finished? Raw steel? Primed? black paint?? Also...same question for the timing cover. To replicate original one would have to remove timing cover and get it in the finish state it was in upon install...which was.....what? Then...when spraying the assembly the finish on back of the balancer would remain as installed and only the timing cover areas accessible by spray would be engine orange.

Next...front seal. Thanks as I would not have thought to replace it but...as we know...while I am in there.... That said....and given my comments above...would seem best to remove the timing cover to both deal with the finishing of it and easier to replace front seal. My noob question here is...do I need to drain the oil prior to removing timing cover?? It does appear to be some grease/oil on the front of the engine adjacent to the timing cover so I think a new timing cover gasket would be wise....while I am in there....lol.

Bonus point...I did see a marking on my timing cover roughly in center of the front of "6 70". If that is intended to translate to June 1970 it would be a replacement on my late Oct 1969. Not that I am gonna start chasing a date correct timing cover.....or am I ?? rabbit hole #83...lol

[Keith M.]

Re: Harmonic Balancer Code question(s)

Keith------

For the most part, my source of information on your question was my own, personal knowledge. The only thing I had to look up was the date of discontinuation of the 3947712 balancer.

In general, information on questions like yours can be found in old editions of the P&A catalogs or other references which are difficult, if not impossible, for most to obtain.

By the way, the 3942538 seen on the hub section of the balancer you pictured is the casting number for the hub section and is not the part number of a finished balancer assembly.

Thank you again for so generously sharing your knowledge and experience.

[John S.]

8F122E1D-B7F0-4142-A181-223AD7BB0DF8.jpg

9DA2535E-79CA-447A-9D6B-A4A87904E1B0.jpg

[Donn M.]

Re: Harmonic Balancer Code question(s)

Keith, Sorry I didn't get back to you sooner. I left the back of my damper in primer. No need for orange and don't want rust. Just my choice. On mine I had to remove the pan to remove the timing chain cover and wanted replace the rear seal anyway. Good time to remove and clean the oil pump. Glad I did as the little white plastic sleave was cracked. I'm not the one to talk to about chasing the absolute correct original paint coverage (or lack of) details. I do what looks best to me and take the minor hit in judging when "too nice".
Good luck on your project. Donn

[Joe R.]

Re: Harmonic Balancer Code question(s)

Keith-----

The original balancer for your application was GM #3947712. That balancer was used for 1969-70 L-46 as well as 1970-71 LT-1. The GM #6272224 was first used for 1972 LT-1 and became SERVICE for the referenced 1969-71 applications when the 3947712 was discontinued in July, 1972.

Except for the various stamped codings, the 3947712 and 6272224 are identical with respect to configuration and cannot be told apart.

Hi Joe:

Regarding your statement that the 3947712 and 6272224 are identical and cannot be told apart, I think there is an interesting difference between the early SHP balancers and the later ones. It appears that this change first appeared on the 6272224 and may be present on every service replacement that came after the 6272224.

The first photo below shows this difference. The second photo, which is from an ebay listing, shows the same feature appearing on the currently available service replacement 19260269.

Up until the 6272224, the SHP balancers had an inertia ring that was approximately 1.71" wide and was mounted on a hub that was also about 1.71" wide.

On the sample 6272224 that I have, the width of the inertia ring has been reduced to 1.61" except for a small "collar" near the hub. This collar is approximately .125" high. The hub casting is the same 3942538 that was used in the full-width, non-finned balancers that preceded the 6272224.

Do you have any idea why this change was made for the 1972 LT-1? I suspect that GM altered the design to gain a bit more clearance between the back of the intertia ring and some other part that may have been new for the 1972 LT-1.

[Joseph W.]

Re: Harmonic Balancer Code question(s)

How does one know if their harmonic balancer needs rebuilding?

[John S.]