72 LT1 timing tab

[Fred H.]

Does anyone sell a correct 72 LT1 replacement timing tab? Presently our LT1 (8" harmonic balancer) has what apparently is a 71 LT1 timing tab and we would like to replace it for judging purposes.

[David L.]

Re: 72 LT1 timing tab

Fred,
IN my 40 year collection of parts I do have a NOS timing tab, GM # 3991436, for a 72 Corvette w/SHP 350.
Dave

[David H.]

Re: 72 LT1 timing tab

Does anyone sell a correct 72 LT1 replacement timing tab? Presently our LT1 (8" harmonic balancer) has what apparently is a 71 LT1 timing tab and we would like to replace it for judging purposes.

Fred

What is the assembly date of your engine?

Dave

[Fred H.]

Re: 72 LT1 timing tab

Hi Dave, the casting date is F 10 72 the build date is 7/21/1972

[Fred H.]

Re: 72 LT1 timing tab

To hopefully clarify my inquiryimage000000014.jpg I've attached photo that represents the correct 72 LT1 (8" harmonic balancer equipped) timing tab.

[Joe L.]

Re: 72 LT1 timing tab

To hopefully clarify my inquiry[ATTACH=CONFIG]108998[/ATTACH] I've attached photo that represents the correct 72 LT1 (8" harmonic balancer equipped) timing tab.

Fred------


How do you know that this is a correct configuration 1972 LT-1 timing tab?

[Leonard M.]

Re: 72 LT1 timing tab

Joe, His picture looks identical to the original shown in the J.G., Fig, M 8.9

[Fred H.]

Re: 72 LT1 timing tab

Reference 1970 -1972 7th edition TiM & JG pages 138 -139NCRS tt 2.jpgncrs tt 1.jpg

[Fred H.]

Re: 72 LT1 timing tab

I recently received a alleged correct photo 72 LT1 timing tab, from (a restored)
survivor (with an November 71 build date). This timing tab looks the 71 tab (in the TIM / JG) ?

Jim 2.jpg



Jim Steele's.jpg

[Terry M.]

Re: 72 LT1 timing tab

I recently received a alleged correct photo 72 LT1 timing tab, from (a restored)
survivor (with an August or September 71 build date). This timing tab looks the 71 tab (in the TIM / JG) ?


[ATTACH=CONFIG]109011[/ATTACH]

I suggest you begin to track the engine build dates of the examples you are seeing. In the TIM&JG the word "typical" carries a lot of weight. It basically means that we haven't tracked the examples cited. Yopu would be doing yourself and many others taking on this task.

[Fred H.]

Re: 72 LT1 timing tab

I'm attempting to determine when GM began using the the 72 tag (from the 71 timing I believed used in the early 72 production run) as referenced in the TIM / JG

Hopefully I will receive some additional input on any survivor 72 LT1's (and be possibly able to correlate the date GM started using what is really OEM correct.

[Joe L.]

Re: 72 LT1 timing tab

I recently received a alleged correct photo 72 LT1 timing tab, from (a restored)
survivor (with an November 71 build date). This timing tab looks the 71 tab (in the TIM / JG) ?

[ATTACH=CONFIG]109012[/ATTACH]



[ATTACH=CONFIG]109011[/ATTACH]

Fred------


This is the only configuration of the 1971-80 8" balancer timing pointer that I am aware of. The only part number ever catalogued by GM for this part is 3991436. It's possible there were 2 configurations of this part number but every known example of the 3991436 that I have ever seen is of the configuration pictured here.

[Fred H.]

Re: 72 LT1 timing tab

That's the timing tab we have. I began chasing the issue when e received a deduction (mechanical page 2 #8 distributor & coil) with the note "timing tab is 71 SB like Fig M 8.9". If that is correct we'll accept it, however there appears to be both 71 & 72 tabs used in the 72 production run?

[David L.]

Re: 72 LT1 timing tab

I am sure that Chevrolet used up the 71 tabs until they were all gone and probably mixed them up with 72 tabs. Neither I or Joe has ever found GM part numbers for the 71 or 72 tabs because apparently the different part numbers do not exist. GM was in the business to make money and substitutions on the assembly were sometimes necessary.
As best as I can recall the assembly line ran out of 1965 grills near the end of 1965 production so they installed 1966 grills on late 1965 Corvettes.
Dave

[Gary B.]

Re: 72 LT1 timing tab

The tab in the 70-72 TIM&JG is from 72 LT1 VIN 20571. Very original, unrestored car. J04 (May) build date.
Gary B