1970 LT1 Crank Pulley Bolts

[James H.]

Can anyone tell me the proper finish (color) of the three bolts that hold the crank pulley to the harmonic balancer as well as the finishes on the center thick washer, bolt and tooth washer that bolts to the end of the crank and through the center of the crank pulley?

I have the TI Manual for 1970, but I don;t seen a picture or detail about it there. Best would be a picture if anyone has one?

Thanks in Advance

Jim

[Joe L.]

Re: 1970 LT1 Crank Pulley Bolts

Can anyone tell me the proper finish (color) of the three bolts that hold the crank pulley to the harmonic balancer as well as the finishes on the center thick washer, bolt and tooth washer that bolts to the end of the crank and through the center of the crank pulley?

I have the TI Manual for 1970, but I don;t seen a picture or detail about it there. Best would be a picture if anyone has one?

Thanks in Advance

Jim

Jim------


The balancer pulley bolts were supposed to be 3/8-24 X 5/8", GM-280M material (3 lines), zinc finish, and non-indented (trimmed) head. However, I would not be surprised if at least some were built using the base engine bolts. These were 3/8-24 X 3/4", GM 280M, phosphate finish, and non-indented head.

I believe the pulley bolt washers were zinc plated split lock washers but if the standard engine bolts were used, probably phosphate or natural finish.

The crankshaft bolt was 7/16-20 X 2-1/4", GM 300M material (6 lines), phosphate finish, and non-indented head.

The lockwasher was an external tooth lockwasher, natural finish

The large flat washer was natural finish

[Ron G.]

[Ron G.]

[Terry M.]

Re: 1970 LT1 Crank Pulley Bolts

Ron
I believe the front of the damper was covered, or somehow shielded from paint so that any pulley(s) added later had a flat surface to contact. No paint drips to throw pulley(s)s out of true.

[Joe L.]

Re: 1970 LT1 Crank Pulley Bolts

James,

I should’ve mentioned this in my prior thread. Although the bolts were plated black oxide or black phosphate they received orange engine paint as the harmonic balance was attached when the engine was painted.

Ron------


The harmonic balancer was installed at the engine plants. However, the pulley, pulley bolts and crankshaft center bolt was installed at St. Louis.

[Joe L.]

Re: 1970 LT1 Crank Pulley Bolts

Ron
I believe the front of the damper was covered, or somehow shielded from paint so that any pulley(s) added later had a flat surface to contact. No paint drips to throw pulley(s)s out of true.

Terry------


Yes, but only the slightly raised portion of the balancer hub's face where the pulley seats was masked off or otherwise protected from paint. The rest of the exposed portion of the balancer was painted with the engine.

[Ron G.]

Re: 1970 LT1 Crank Pulley Bolts

Joe,

My bad. I was thinking of the harmonic balancer and not the pulley that attaches to it.

- Ron

[Joe L.]

Re: 1970 LT1 Crank Pulley Bolts

All------


I'd be very interested to learn what the finish is of the 3 balancer PULLEY bolts that folks with original 1970-72 find on their engines. Is it zinc or phosphate?

[Ron G.]

[Joe L.]

Re: 1970 LT1 Crank Pulley Bolts

Joe,

phosphate. I’m not sure about the front of the harmonic balancer, but if Joe and Terry says that it was masked then I believe it. However, I know that the backside of the harmonic balancer did not receive any paint.

Ron------


...and, just to confirm, you're referring to the 3 balancer pulley bolts, not the center crankshaft bolt? The center crankshaft bolt was definitely phosphate.

If the pulley bolts are phosphate that means that the base engine bolts, GM #9423959, were used rather than the bolts scheduled for the LT-1 application, GM #181629. The 9423959 were phosphate; the 181629 were zinc. Both should be GM 280M material (3 lines).

It would be nice to hear from some others to try to determine if it was all LT-1's that got the base engine bolts or just some.

[Terry M.]

Re: 1970 LT1 Crank Pulley Bolts

All------


I'd be very interested to learn what the finish is of the 3 balancer PULLEY bolts that folks with original 1970-72 find on their engines. Is it zinc or phosphate?

1970 LT1 s/n 14,544

1970 LT1 sn 14544.jpg

[James H.]

Re: 1970 LT1 Crank Pulley Bolts

Ron,

Are you saying that the center bolt and large washer and the 3 bolts that screw into the harmonic balancer, were screwed into the balancer, and the end of the crankshaft when the engine was painted orange, then removed to put on the black colored crank pulley, leaving all 4 bolts and washers painted orange?

Thanks

Jim

[Joe L.]

Re: 1970 LT1 Crank Pulley Bolts

1970 LT1 s/n 14,544

[ATTACH=CONFIG]100856[/ATTACH]

Terry-------


Here it appears that the pulley bolts were phosphate finished (now deteriorated to rust). I've always kind of figured that the LT-1 engines would not have received the zinc plated pulley bolts that the AIM specified (GM #181239). The line workers probably "simplified things" by using the standard engine bolt, GM #9423959, for all applications.

The big surprise here is the center bolt. The bolt specified for all 69+ small blocks was GM #9428643. This is a phosphate-finished bolt. The bolt I see is a zinc plated bolt. A zinc plated bolt was used for 1963-68 SHP small blocks but that bolt had a safety wire hole through the head. So, I don't know what this bolt is.

[Terry M.]

Re: 1970 LT1 Crank Pulley Bolts

All------


I'd be very interested to learn what the finish is of the 3 balancer PULLEY bolts that folks with original 1970-72 find on their engines. Is it zinc or phosphate?

Not to confuse the issue, but this is a 1972 base motor with 10K miles. It happened to be available to photograph.

1972 Base 10Kmi.jpg