1970 LT-1 Initial Timing Spec change documentation
Hi everyone! I am a devoted follower of Duke Williams with his expertise of ignition timing and its evolution in the anti-smog (anti-performance) era. I think y'all may find the following factual tidbit interesting, as I believe it reveals a bit of the "de-tuning" efforts ongoing when the 1970 LT-1 was released into production in Feb 1970.
When the 1970 Chassis Service Manual was printed in 1969, it is interesting to note that the 1970 Corvette was not included in it. Instead, it specifically stated "1969 CORVETTE" on the cover. In reading the specification section at the end of the manual however, section 6Y, Engine Electrical, under sub-section DISTRIBUTORS, it nicely lists engine description and availability with the distributor P/N and mechanical and vacuum attributes. Knowing that this publication was released well before the introduction of the 1970 Corvette, it interesting to note an entry "350 Cu. In. V-8 - 370 HP RPO LT7, Corvette w/ RPO K-66". The most interesting of this entry is the Ignition timing BTDC at Engine Idle specification of 14 deg BTDC. We all know that the "production" setting of the LT-1 was 8 deg BTDC ... a whole 6 degrees retarded from that initial publication. And while one may speculate that the LT7 was something different, the entry above that one was described as 370 HP LT1, Corvette (but had a point distributor associated with it) with the identical 14 deg initial spec.
While I subscribe to Duke's timing method of letting the initial setting be what it may after achieving the 34-36 deg total mechanical advance before 3,000 crank rpm, I do find it interesting that it appears the good folks at Chevrolet intended more advance than what ended up in production after the February 1970 introduction.
I have my Mr. Gasket 928G Dist. Spring kit and the B28 Vac Adv equiv (WVE 4V1053 from Rock Auto) on order and looking forward to better response and performance over the stock settings.
When the 1970 Chassis Service Manual was printed in 1969, it is interesting to note that the 1970 Corvette was not included in it. Instead, it specifically stated "1969 CORVETTE" on the cover. In reading the specification section at the end of the manual however, section 6Y, Engine Electrical, under sub-section DISTRIBUTORS, it nicely lists engine description and availability with the distributor P/N and mechanical and vacuum attributes. Knowing that this publication was released well before the introduction of the 1970 Corvette, it interesting to note an entry "350 Cu. In. V-8 - 370 HP RPO LT7, Corvette w/ RPO K-66". The most interesting of this entry is the Ignition timing BTDC at Engine Idle specification of 14 deg BTDC. We all know that the "production" setting of the LT-1 was 8 deg BTDC ... a whole 6 degrees retarded from that initial publication. And while one may speculate that the LT7 was something different, the entry above that one was described as 370 HP LT1, Corvette (but had a point distributor associated with it) with the identical 14 deg initial spec.
While I subscribe to Duke's timing method of letting the initial setting be what it may after achieving the 34-36 deg total mechanical advance before 3,000 crank rpm, I do find it interesting that it appears the good folks at Chevrolet intended more advance than what ended up in production after the February 1970 introduction.
I have my Mr. Gasket 928G Dist. Spring kit and the B28 Vac Adv equiv (WVE 4V1053 from Rock Auto) on order and looking forward to better response and performance over the stock settings.
Comment