C2 L79 Harmonic Balancer ID/Questions

[Frank C.]

Re: C2 L79 Harmonic Balancer ID/Questions

Bob,

I have attached pictures. The timing mark is lined up with the keyway. The width of the balamcer is 1.670.

Frank

IMG_1657.jpgIMG_1654.jpg

[Bob J.]

Re: C2 L79 Harmonic Balancer ID/Questions

Frank,
thanks for the measurement.
I'll measure one at work tomorrow and report back.
Bob

[Scott S.]

Re: C2 L79 Harmonic Balancer ID/Questions

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

Larry,

Do you know whether your three short crankshaft pulley bolts are indented hex with attached internal tooth washer, or separate bolt and split lock washer? Do you know the grade and headmark? Mine appear to be the three bolts called out in the AIM for the 300hp engine, they look the same as those in Frank's photos, no grade lines, "E" headmark w/att ITW. I thought I had incorrect bolts for this location on an L79 engine, I'd be happy to find out I'm wrong

[Scott S.]

Re: C2 L79 Harmonic Balancer ID/Questions

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". (bold-face emphasis mine)

Joe,

My crankshaft pulley bolts appear to be the same as Frank's, indented hex with attached internal-tooth washer, "E" headmark, flat tip, no grade marks (implying Grade 2). The 1965-67 AIMs all show the same Bolt part numbers for these same applications for all three model years:

Base engine:
GM 3784349 Bolt Asm, base engine (UPC 6-A3, 1965-67, also base engine for 1963-64)

L79:GM 181629 Bolt + GM 103321 Lock Washer (UPC L76-2 for 1965 AIM) (UPC L79-A1 for 1966-67)

L79 + N40 + C60:GM 181635 Bolt, no lock washer call-out (UPC N40-6 for 1965 AIM) (UPC N40-A6 for 1966-67)


ALL small block crankshaft pulley applications, 1963-1967?

[Larry M.]

Re: C2 L79 Harmonic Balancer ID/Questions

Larry,

Do you know whether your three short crankshaft pulley bolts are indented hex with attached internal tooth washer, or separate bolt and split lock washer? Do you know the grade and headmark? Mine appear to be the three bolts called out in the AIM for the 300hp engine, they look the same as those in Frank's photos, no grade lines, "E" headmark w/att ITW. I thought I had incorrect bolts for this location on an L79 engine, I'd be happy to find out I'm wrong

Scott:

My main center attaching bolt is a Grade 8, TR headmark with the hole drilled through the head. It has an external tooth washer beneath this bolt head.

The three smaller pulley attaching bolts are Grade 2, E headmark with an internal tooth washer under the head of each.

My car looks pretty much like the single picture that Frank posted above (Post #7).

Larry

[Scott S.]

Re: C2 L79 Harmonic Balancer ID/Questions

Scott:

My main center attaching bolt is a Grade 8, TR headmark with the hole drilled through the head. It has an external tooth washer beneath this bolt head.

The three smaller pulley attaching bolts are Grade 2, E headmark with an internal tooth washer under the head of each.

My car looks pretty much like the single picture that Frank posted above (Post #7).

Larry

[Timothy B.]

Re: C2 L79 Harmonic Balancer ID/Questions

Scott,

Here are pictures of the bolts on my 63 car. I remember they are short but not sure if 1/2" or 5/8" long.

[Bob J.]

Re: C2 L79 Harmonic Balancer ID/Questions

HI Frank,
I measured a NOS one and got 1.706.
I'm guessing the one you have is a service replacement because I've not seen those numbers/letters cast into the front outer ring except on service replacements.
Bob

[Scott S.]

Re: C2 L79 Harmonic Balancer ID/Questions

Scott,

Here are pictures of the bolts on my 63 car. I remember they are short but not sure if 1/2" or 5/8" long.

Tim,

Thanks very much for the pictures. I checked the '63 AIM and found the addition of the Gr8 harmonic balancer center bolt for 300hp and 340hp (L75, L76, Sheet 2) and 360hp (L84, Sheet 2), but did not see any changes to the three bolts that secure the crankshaft pulley for optional engines vs. the base engine set-up in 1963. It looks like the same situation for 1964. It's not until 1965 that the Grade 5 crankshaft pulley bolts show up for SHP small blocks in the AIM. If the Grade 2 bolts were good enough for the higher HP engines in 1963 & 1964, I wonder why the change (in the AIMs) for 1965-67, and why this change was apparently never implemented on the Production Line?

[Scott S.]

Re: C2 L79 Harmonic Balancer ID/Questions

Bob,

I have attached pictures. The timing mark is lined up with the keyway. The width of the balamcer is 1.670.

Frank

[ATTACH=CONFIG]41974[/ATTACH][ATTACH=CONFIG]41975[/ATTACH]

Frank,

I measured my '67 L79 balancer (no fins), it is 1.703" wide.

[Michael M.]

Re: C2 L79 Harmonic Balancer ID/Questions

Hi Frank, In the "Corvette by the Numbers" book, the finned 8 inch balancer was used in 62-65 small blocks of 340HP and higher. It was the third small block harmonic balancer design for small blocks made between '55 and '82, and the first 8 inch. The 66-68 L79 and the 69-82 350 C.I. engines used the fifth design, also 8 inch but with no fins. The pictures of it in the book match your pictures but, for some reason, the Corvette by the Numbers book doesn't have any part numbers for this part. I have the 66 L79 with PS and no AC and I have the finned balancer as called for in the Judging Guide. My car was built March 22, 1966. There is a definite discrepancy between the JG and the Corvette by the Numbers book. Who knows which is actually correct. They may have used both parts and at different times, depending on what was on hand on a particular day. Maybe I'll get under there later and measure it as well. Mike

[Frank C.]

Re: C2 L79 Harmonic Balancer ID/Questions

All,

Again thanks to all who have shared their knowledge. I want to throw something out there for consideration. I know Scott Smith, Larry Mulder and myself have L79 w/AC. All of our engines have the 8 " Balancer with no fins. Is it possible these balancers were used for this option?

Frank

[Joe L.]

Re: C2 L79 Harmonic Balancer ID/Questions

All,

Again thanks to all who have shared their knowledge. I want to throw something out there for consideration. I know Scott Smith, Larry Mulder and myself have L79 w/AC. All of our engines have the 8 " Balancer with no fins. Is it possible these balancers were used for this option?

Frank

Frank-----


I can's say for sure but I highly doubt that different balancers were used for L-79 engines with A/C.

Something that I think is highly possible, though, is that 66-67 L-79's seen with finned balancers got those balancers because the JG says that's how they are supposed to be.

[Frank C.]

Re: C2 L79 Harmonic Balancer ID/Questions

Joe,

I am going to clean the balancer I have up, repaint and use as is. Thanks again for the help.

Frank

[Brian K.]

Re: C2 L79 Harmonic Balancer ID/Questions

Joe, my 66 L79 has been in the family since 1972 and has its born with engine with 40K miles. Its got the finned balancer with a stamped date A66 on the back side outer ring. So I can say for sure that a least some 66's got the finned balancer judging guide or not.