Did the 1972 ZR1 have a Transistor Ignition System?

[Marvin B.]

Hello,

I have been doing research on Transistor Ignition Systems both at the broader General Motors level as well as specific to Corvettes. I am trying to determine whether the 20 1972 ZR1 cars were equipped with a TI system or did they have a points distributor like the standard LT-1 had for 1972. In other words, did TI go away completely on Corvettes (Including ZR1s) after the 1971 model year? Thanks. Marvin

[Joe L.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Hello,

I have been doing research on Transistor Ignition Systems both at the broader General Motors level as well as specific to Corvettes. I am trying to determine whether the 20 1972 ZR1 cars were equipped with a TI system or did they have a points distributor like the standard LT-1 had for 1972. In other words, did TI go away completely on Corvettes (Including ZR1s) after the 1971 model year? Thanks. Marvin

Marvin-----


There was no TI after 1971 for any Corvette application. So, no 1972 Corvette was so-equipped.

By the way, there was nothing special about the LT-1 engine used for any 1970-72 ZR-1. The ZR-1 was a performance package which included the same LT-1 engine used for non ZR-1 LT-1 equipped Corvettes.

[Marvin B.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Joe, thanks for your reply.

[Duke W.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Marvin-----


There was no TI after 1971 for any Corvette application. So, no 1972 Corvette was so-equipped.

By the way, there was nothing special about the LT-1 engine used for any 1970-72 ZR-1. The ZR-1 was a performance package which included the same LT-1 engine used for non ZR-1 LT-1 equipped Corvettes.

Joe - didn't the LT-1 that was part of the ZR-1 package have a unique engine code because it was equipped with the L-88 flywheel and 10.5" clutch rather than the standard heavy flywheel and 11" clutch that was used on non-ZR-1 LT-1s?

Duke

[James G.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Duke,
Yes they had the 10.5 flywheel which weighed 15# less with a 403 bell housing. If I am not mistaken they were also equipped with the 6 quart oil pan which was on the first 1970 LT1's CTU coded engines and this of course negates power steering as an option.

[Kenneth B.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Starter on my old one that I sold 72 ZR-1 the last one by the way was also the same as the 69 L-88 7 all the different parts were dated in 1969.

[Joe L.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Joe - didn't the LT-1 that was part of the ZR-1 package have a unique engine code because it was equipped with the L-88 flywheel and 10.5" clutch rather than the standard heavy flywheel and 11" clutch that was used on non-ZR-1 LT-1s?

Duke

Duke------


Yes, it did. They also did have the "6 quart" oil pan as others have mentioned (although early 1970 LT-1 also used this oil pan). I guess when I responded above I was thinking more in terms of performance-related differences.

[Marvin B.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Thanks very much for the great information. Regarding the L88 flywheel/starter/bell housing, my understanding is that the only 1970-1972 Corvettes which had these parts were the ZR1 cars. None of the 454 cars including the LS-6 and LS-6-equipped ZR2s had this set up because all 454s were external balanced cranks. Is this correct?

[James G.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

15# less rotating weight is WORTH seconds on a road racing track, accelerating up and down through the gears takes horsepower to sling the flywheel.
It does make a difference in a 1969 Z28... they have the light flywheels with 10.5 clutch as well, I had a 69 Z that had an 11" clutch after putting the correct one back it was a different engine.
A few ounces out of the reciprocating weight will do wonders... every piston, pin, ring pack, and small end of the rod must be accelerated from a dead stop 2 times every rotation of the engine.

[Joe L.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Thanks very much for the great information. Regarding the L88 flywheel/starter/bell housing, my understanding is that the only 1970-1972 Corvettes which had these parts were the ZR1 cars. None of the 454 cars including the LS-6 and LS-6-equipped ZR2s had this set up because all 454s were external balanced cranks. Is this correct?

Marvin------


Yes, during the 1970-72 period only ZR-1 Corvettes were equipped with the 12-3/4" flywheel with 10.4" clutch. All LS-6, except those equipped with THM-400, used a dual disc clutch with a special 14" flywheel and 10" friction discs. All other 1970-72 Corvettes used a 14" flywheel with 11" clutch.

[Marvin B.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Thanks James!

15# less rotating weight is WORTH seconds on a road racing track, accelerating up and down through the gears takes horsepower to sling the flywheel.
It does make a difference in a 1969 Z28... they have the light flywheels with 10.5 clutch as well, I had a 69 Z that had an 11" clutch after putting the correct one back it was a different engine.
A few ounces out of the reciprocating weight will do wonders... every piston, pin, ring pack, and small end of the rod must be accelerated from a dead stop 2 times every rotation of the engine.

[Marvin B.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Thanks Joe!

Marvin------


Yes, during the 1970-72 period only ZR-1 Corvettes were equipped with the 12-3/4" flywheel with 10.4" clutch. All LS-6, except those equipped with THM-400, used a dual disc clutch with a special 14" flywheel and 10" friction discs. All other 1970-72 Corvettes used a 14" flywheel with 11" clutch.

[Joe L.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

15# less rotating weight is WORTH seconds on a road racing track, accelerating up and down through the gears takes horsepower to sling the flywheel.
It does make a difference in a 1969 Z28... they have the light flywheels with 10.5 clutch as well, I had a 69 Z that had an 11" clutch after putting the correct one back it was a different engine.
A few ounces out of the reciprocating weight will do wonders... every piston, pin, ring pack, and small end of the rod must be accelerated from a dead stop 2 times every rotation of the engine.

James------


For racing applications, there are advantages to a lighter flywheel and pressure plate assembly. However, for STREET applications (which is where the vast majority of us actually use our cars), I vastly prefer a larger, heavier flywheel. GM thought so, too. From 1969 to 1981 GM only manufactured 171 Corvettes with a 12-3/4", lightweight flywheel (and, no Corvettes with a standard weight 12-3/4" flywheel).

12-3/4" flywheels were used for all 1963-68 small blocks (and 1967-69 Z-28 Camaros) but they were not the lightweight version. Of course, they are lighter than the 14" flywheels but they were not the same as those used for above-referenced 171 Corvettes (and, also used for 1965 L-78).

[Marvin B.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Joe,

I was wondering how you arrived at 171 cars from 1969 through 81. I came up with 154 (99 1969 M22 equipped L-88s, 2 1969 ZL-1s, and 53 1970-72 ZR1s. The 17 difference appears to be the number of 1969 THM400 equipped L88s. Am I missing some?

Marvin

James------


For racing applications, there are advantages to a lighter flywheel and pressure plate assembly. However, for STREET applications (which is where the vast majority of us actually use our cars), I vastly prefer a larger, heavier flywheel. GM thought so, too. From 1969 to 1981 GM only manufactured 171 Corvettes with a 12-3/4", lightweight flywheel (and, no Corvettes with a standard weight 12-3/4" flywheel).

12-3/4" flywheels were used for all 1963-68 small blocks (and 1967-69 Z-28 Camaros) but they were not the lightweight version. Of course, they are lighter than the 14" flywheels but they were not the same as those used for above-referenced 171 Corvettes (and, also used for 1965 L-78).

[Joe L.]

Re: Did the 1972 ZR1 have a Transistor Ignition System?

Joe,

I was wondering how you arrived at 171 cars from 1969 through 81. I came up with 154 (99 1969 M22 equipped L-88s, 2 1969 ZL-1s, and 53 1970-72 ZR1s. The 17 difference appears to be the number of 1969 THM400 equipped L88s. Am I missing some?

Marvin

Marvin------


Yes, I forgot to take into consideration the 1969 L-88's and ZL-1 with M-40. So, there's actually even fewer 1969-81 Corvettes with 12-3/4", lightweight flywheels.