L-71/L89

[Warren F.]

Does anyone know why this engine combination used 3/8ths rod bolts and pushrods, instead of the HD 7/16ths units like L-88's, ZL-1's & LS-6's?

[Michael H.]

Re: L-71/L89

Warren,

The L71 and L89 were designed for a completely different life style than the L88/ZL1. L88 and ZL1 were competition engines designed to operate in a higher RPM range for extended periods of time, and produced more horse power, which required more durable components. At road racing events, for example, these engines would be expected to operate in a 5000 to 7500 RPM range for hours at a time. The street version L78, L71 and L72 etc engines were designed to be very durable in their own work/RPM range, and they were. Engineering felt that the HD 7/16" rod bolts were not required for these engines.

Michael

[Dick W.]

Re: L-71/L89

Warren, probably so that they could spend more money on warranty claims. Helps explain why you see so many "restoration" engines

[Warren F.]

Michael & Dick..... thanks, Warren *NM*

[Mark #28455]

Re: L-71/L89

Didn't the original L88's use the 3/8" bolts? I thought the change to the 7/16 boron bolts happened for the 1969 model year.
Thanks,
Mark

[Michael H.]

Re: L-71/L89

Mark,

You are correct. I believe 69 was the first year for the 7/16" bolt. I know 67 was 3/8" and I'm pretty sure 68 was also.

[Joe L.]

Re: L-71/L89

Michael. Mark, et al----

1969 was the first year for the 7/16" bolt rods for L-88s, although very late 1968 may have used them, too. This was the GM #3969804 rod. This was the strongest and most expensive rod that GM ever used for a PRODUCTION big block. It was used ONLY for L1968-1969 L-88 and ZL-1. It was actually available in SERVICE until only a few years ago. However, the cost of it was such that an even better set of aftermarket rods could be purchased for less than a set of these.

1971 LS-6 also used a 7/16" bolt rod. However, it was NOT the the 3969804. Instead, it was a somewhat less robust rod of GM #3963552. It had a somewhat smaller cross section and used knurled shank rod bolts rather than the hardened and ground, boron steel bolts used for the 3969804 rod. Still, the LS-6 rod was a very stout rod that will be more than adequate for any street big block application and is an excellent upgrade for any 1965-74 Corvette big block originally fitted with 3/8" bolt rods. An improved version can be purchased under GM #10198922.

Except for L1968-1969 L-88 and ZL-1 as well as 1971 LS-6, all Corvette big blocks used 3/8" bolt rods.

[Dick W.]

Re: L-71/L89

Joe, good to see you back. I assume that you have had your yearly fill of New England, relatives and last, but not least, lobstah

[Joe L.]

Re: L-71/L89

Dick-----

Yes, I did. The lobster total was 31 when all was said-and-done.