Recommended spark plugs for 492 angle plug heads
Hi everyone! While not a question for pure factory stock LT-1 engines, I have the "over-the counter" Chevy 492 angle plug heads on a 1971 LT-1 block. The question involves the recommended type of spark plug - extended tip or not.
According to the AMA data published by Chevrolet, the stock engine plug data for the following years of LT-1 engines are:
1970 - AC R44 (13/16", gasket seal)
1971 - AC R43TS (5/8", tapered, extended tip)
1972 - AC R44T (5/8", tapered)
From the research performed on this site and others, extended tipped plugs tend to run hotter, and perhaps explains why the change in heat range spec from 44 to 43 for the extended and back to 44 when extended tip was deleted?
I suppose my question, besides plug recommendation with the angle plug head, is why the change in spec from extended tip back to standard tip length from 71 to 72? Did the Chevrolet engineers discover something not optimum with the extended tipped plugs? (and conversely why did they go extended for '71?) A cost/benefit effect of the GM deproliferation program?
Thanks!
According to the AMA data published by Chevrolet, the stock engine plug data for the following years of LT-1 engines are:
1970 - AC R44 (13/16", gasket seal)
1971 - AC R43TS (5/8", tapered, extended tip)
1972 - AC R44T (5/8", tapered)
From the research performed on this site and others, extended tipped plugs tend to run hotter, and perhaps explains why the change in heat range spec from 44 to 43 for the extended and back to 44 when extended tip was deleted?
I suppose my question, besides plug recommendation with the angle plug head, is why the change in spec from extended tip back to standard tip length from 71 to 72? Did the Chevrolet engineers discover something not optimum with the extended tipped plugs? (and conversely why did they go extended for '71?) A cost/benefit effect of the GM deproliferation program?
Thanks!