C2 L79 Harmonic Balancer ID/Questions

[Frank C.]

Good Morning,

I am rebuilding the 327/350 L79 from my 66, and need some advise and help. In addition to L79, the car has ac and ps. I have posted pictures of the Harmonic Balancer and the pulleys attached to the balancer.

From the archives and 66 TM it looks like I should have a finned GM # 3817173 8" Harmonic Balancer that has 12 fins cast into the backside. The 66 TM shows I should have 3 pulleys.

My questions:

1. Is this the correct Harmonic Balancer? The balancer I pulled from my engine looks to be a replacement based on no cast part number and no fins.

2. Does the pulley configuration look correct?

3. Are the bolts holding the pulleys to the balancer coreect?

4. Does the bolt attaching the balancer look correct? The bolt head which attaches the balancer to the cranshaft is drilled through the head. holding the crank.



IMG_1653.jpgIMG_1648.jpgIMG_1649.jpgIMG_1651.jpg

Frank

[Loren L.]

Re: C2 L79 Harmonic Balancer ID/Questions

My '65 is a late car (#23561) w/L79, A/C, TI & PS. My crankshaft pulleys conform to yours; the single belt pulley is stamped with an "S" on the back; the 2 belt pulley is stamped "3858553" and with a "GM" and an "S" on its face.
You need the finned 8" balancer; the pulley bolts conform to what I found on my car - can't locate to read the logo - and it appears to be the correct balancer bolt and washer. The hole in the bolt head is for the possible use of safety wire

[Brian K.]

Re: C2 L79 Harmonic Balancer ID/Questions

My March 4th build 66 L79 has the finned balancer dated A66, my car has PS but no AC.

[Gene M.]

Re: C2 L79 Harmonic Balancer ID/Questions

Frank,
Most of the 7/16 TR crank bolts do not have the cross drilled hole. From my experience about 1 out of 10 has the hole. That is a neat oddity to have. Most are also TR marked but always grade 8 bolts.

Make sure if you acquire a correct finned balance that the keyway and the timing line are aligned.

[Joe L.]

Re: C2 L79 Harmonic Balancer ID/Questions

Good Morning,

I am rebuilding the 327/350 L79 from my 66, and need some advise and help. In addition to L79, the car has ac and ps. I have posted pictures of the Harmonic Balancer and the pulleys attached to the balancer.

From the archives and 66 TM it looks like I should have a finned GM # 3817173 8" Harmonic Balancer that has 12 fins cast into the backside. The 66 TM shows I should have 3 pulleys.

My questions:

1. Is this the correct Harmonic Balancer? The balancer I pulled from my engine looks to be a replacement based on no cast part number and no fins.

2. Does the pulley configuration look correct?

3. Are the bolts holding the pulleys to the balancer coreect?

4. Does the bolt attaching the balancer look correct? The bolt head which attaches the balancer to the cranshaft is drilled through the head. holding the crank.



[ATTACH=CONFIG]41918[/ATTACH][ATTACH=CONFIG]41919[/ATTACH][ATTACH=CONFIG]41920[/ATTACH][ATTACH=CONFIG]41921[/ATTACH]

Frank

Frank------

While this balancer does not have the fins, it is a GM #3817171. At some point, the fins were deleted from the 3817171. I believe this deletion occurred very early-on, perhaps as early as 1966 for some balancers.

[Loren L.]

Re: C2 L79 Harmonic Balancer ID/Questions

I have seen finned balancers all the way into the 1968 model year on original L79s.

[Scott S.]

Re: C2 L79 Harmonic Balancer ID/Questions

Good Morning,

I am rebuilding the 327/350 L79 from my 66, and need some advise and help. In addition to L79, the car has ac and ps. I have posted pictures of the Harmonic Balancer and the pulleys attached to the balancer.

From the archives and 66 TM it looks like I should have a finned GM # 3817173 8" Harmonic Balancer that has 12 fins cast into the backside. The 66 TM shows I should have 3 pulleys.

My questions:

1. Is this the correct Harmonic Balancer? The balancer I pulled from my engine looks to be a replacement based on no cast part number and no fins.

2. Does the pulley configuration look correct?

3. Are the bolts holding the pulleys to the balancer coreect?

4. Does the bolt attaching the balancer look correct? The bolt head which attaches the balancer to the cranshaft is drilled through the head. holding the crank.

Frank

Frank,

I am working on restoring a '67 L79 with C60 (no N40). It was my understanding that the original 8" harmonic balancer for 1966 was a one-year only part, GM 3883961, distinguished by an unusual keyway that reverted to the standard keyway in 1967+ as was used in 1965 and earlier. Joe will certainly know more about that. My '67 balancer does not have fins, it seems that many '67s don't, but a fair amount do.

I'm not sure about the pulley configuration, since mine has deep groove pulleys (no power steering), while an L79 with C60 + N40 should have standard groove pulleys. According to page UPC L79-A1 in your 1966 AIM, the three crankshaft pulley bolts should be GM 181629. These should be Grade 5 bolts, 280-M steel, unlike the Grade 2 bolts called out in the base engine section (UPC 6-A3) and shown in your photo.

My harmonic balancer center bolt is a Grade 8 bolt with "TR" headmark and has the hole through the bolt head for a safety wire. This exact same bolt was found on my steering damper to relay rod bracket location (GM 3815933).

[Frank C.]

Re: C2 L79 Harmonic Balancer ID/Questions

Joe and all,
Thanks for the replies. I posted a picture of the Balance center bolt I have. It does have a TR head mark. I plan on keeping the pully and bolt configuration I have. I am still unsure about the balancer. My engine was assembled early April 66. Is there a chance this balancer was installed originally, or should I buy a finned balancer? It looks like this part is available at Paragon.

Frank
IMG_1652.jpg

[Scott S.]

Re: C2 L79 Harmonic Balancer ID/Questions

Frank,

I need to correct something from my previous post. The GM 181629 Gr5 bolts (x3) are correct for L79, but not with power steering. According to the power steering pulley page (UPC N40-A6) the three correct (short) crankshaft pulley bolts are GM 181635. This is also a Grade 5 bolt (stronger steel than your base engine Grade 2 bolts), and slightly longer to account for the thickness of the add-on pulley. According to the GM parts books, GM 181635 is a 3/8-24 x 3/4" Grade 5 bolt.

[Larry M.]

Re: C2 L79 Harmonic Balancer ID/Questions

Frank,

I am working on restoring a '67 L79 with C60 (no N40). It was my understanding that the original 8" harmonic balancer for 1966 was a one-year only part, GM 3883961, distinguished by an unusual keyway that reverted to the standard keyway in 1967+ as was used in 1965 and earlier. Joe will certainly know more about that. My '67 balancer does not have fins, it seems that many '67s don't, but a fair amount do.

I'm not sure about the pulley configuration, since mine has deep groove pulleys (no power steering), while an L79 with C60 + N40 should have standard groove pulleys. According to page UPC L79-A1 in your 1966 AIM, the three crankshaft pulley bolts should be GM 181629. These should be Grade 5 bolts, 280-M steel, unlike the Grade 2 bolts called out in the base engine section (UPC 6-A3) and shown in your photo.

My harmonic balancer center bolt is a Grade 8 bolt with "TR" headmark and has the hole through the bolt head for a safety wire. This exact same bolt was found on my steering damper to relay rod bracket location (GM 3815933).

Scott:

My late March built 1967 has the L79 engine with AC and no PS. Balancer does NOT have fins.....pulleys are deep groove. Low mile (26,000 mile) car.........

Larry

[David L.]

Re: C2 L79 Harmonic Balancer ID/Questions

My 1966 Chev. Parts Catalog (Oct. 1965) lists balancer # 3817173 for 1962-1965 Corvette models w/F.I., S.H.P. (exc. 396) and balancer # 3883961* for 1966 Corvette models w/S.H.P. 327.

* Use with 3883206 key.

According to Chev. Parts History GM # 3883961 was replaced with GM # 3817173 in March 1966 for parts sold over the counter.

My 1967 Chev. Parts Catalogs (April & July 1967) list GM # 3817173 for 1962-1967 Corvette models w/ F.I., S.H.P. along with the note about using key # 3883206.

Key # 3883206 is described in Gr. 0.659 as 3/4" long X 3/16" wide X 1/4" high with the following note: "Used with pulleys and hubs having a shallow (1/16" deep) keyway only. All full depth (1/8") slots take standard woodruff key (106751 two short or 144542 one long) in group 8.960."

In Gr. 8.960, Key # 106751 is described as 3/16" wide by 3/4" long, No. 9 and key # 144542 is described as 3/16" wide by 1 3/8" long, No. 126.


Dave

[Joe L.]

Re: C2 L79 Harmonic Balancer ID/Questions

Joe and all,
Thanks for the replies. I posted a picture of the Balance center bolt I have. It does have a TR head mark. I plan on keeping the pully and bolt configuration I have. I am still unsure about the balancer. My engine was assembled early April 66. Is there a chance this balancer was installed originally, or should I buy a finned balancer? It looks like this part is available at Paragon.

Frank
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Frank------


In my opinion, the balancer you have is original. Among other reasons for this opinion, the configuration of the front of the balancer is pretty much unique to 3817173 balancers manufactured in the 1962 to about the 1970-71 period. After that time, the configuration of the face of the balancer changed. So, that would mean that if this is a non-original balancer, it was replaced sometime during about the 1966 to 1971 period. It's highly unlikely that a balancer would have been replaced during that period of the car's life.

I am very confident that everything you have here, balancer, pullies, and bolts, are original to the car. I would not change any of them. If you do, I think you will be making the car non-original in order to make it "correct".

One curious thing, though, is that I expect this balancer has been painted off the engine at some point since it has more paint coverage on the rear than I would expect to see on a balancer painted with the engine at Flint.

[Dennis O.]

Re: C2 L79 Harmonic Balancer ID/Questions

In an earlier thread, I asked for help in identifying a couple of harmonic balancers I had. I didn't get any definitive answers on that thread. However, one of my balancers looks EXACTLY like the one the OP has. The balancer I have has no stamped part number I can find. It has a couple of faint stamps on the back. One looks like the "Golden Arches" at McDonalds, and the other appears to be "7C". The "7" is pretty definite, but the "C" is a partial stamp. From the contents of this thread, I believe I have a 3817173 non-finned balancer. Does anyone else have an opinion on this? Here is a picture of the balancer inquestion. It is definitely 8" in diameter.Balancers 001.jpgBalancers 003.jpg

[Joe L.]

Re: C2 L79 Harmonic Balancer ID/Questions

In an earlier thread, I asked for help in identifying a couple of harmonic balancers I had. I didn't get any definitive answers on that thread. However, one of my balancers looks EXACTLY like the one the OP has. The balancer I have has no stamped part number I can find. It has a couple of faint stamps on the back. One looks like the "Golden Arches" at McDonalds, and the other appears to be "7C". The "7" is pretty definite, but the "C" is a partial stamp. From the contents of this thread, I believe I have a 3817173 non-finned balancer. Does anyone else have an opinion on this? Here is a picture of the balancer inquestion. It is definitely 8" in diameter.[ATTACH=CONFIG]41965[/ATTACH][ATTACH=CONFIG]41966[/ATTACH]

Dennis------


I would say this is a GM #3817173 (or, if the keyway happens to be 1/16" deep rather than what appears to be 1/8" a GM #3883961).

[Bob J.]

Re: C2 L79 Harmonic Balancer ID/Questions

Hello Frank,
how wide is that balancer?
Does the timing mark on it line up with the center of the keyway?
Bob