Does anyone know what heads (valve size) are on a 1981 L-81 engine? I was thinking that the intakes are 1.94" or smaller, but when I look the head number up, it gives me three different intake valve sizes; 2.02", 1.94" and 1.72". Anyone ever taken one of these engines apart? Thanks in advance.

 

Maybe someone here has the answer: http://www.l81vetteregistry.com/

 

Shark,
Thanks so much f/ the link. I just registered tonight and will get a confirmation when they OK my info, so they say...
I appreciate your passing the info on.

 

Shark,
Still haven't heard from that '81 C-3 Registry. Maybe one needs to be in some "click" inorder to join. Guess I'm not the one. LOL. Maybe when I have some time to kill, I'll re-enter my info and try again. I did see where the site tells that they've had many re-entries to register.
Thanks again.

 

Still no reply from the registry.

 

Did you get my PM?

 

W/ a bunch of cross-referencing from site to site and page to page, I found out that the L-81 'Vette engine, code ZDD, the only engine available that year in that car: W/ block casting #:14010207 (a 4-bolt main block) w/ head casting #: 462624 (1.94" intake/1.50" exhaust valve). This block # can also be a 2-bolt, but the 'Vette got the 4-bolt version, the LM-1 engine. The LM-1 goes all the way back to '68-69 and took the place of the L30 in some vehicles making less HP and more torque.

 

My experience was that the 4-bolt main engines had the 8" harmonic balancer and the 2-bolt main ones had a 6" balancer. Like Hib said, the heads can be machined to accept the larger LT-1/L-82 valves.

 

The casting number of the Corvette block that I listed, comes in 2 or 4 bolt main. However, if the engine is the "ORIGINAL" Corvette engine that came in the car from the factory, then it's the LM-1 which is the 4 bolt version of that casting number.
I've rebuilt many many small block Chevrolet engines over the years and have heard all kinds of tips on what's 2 or 4 bolt, but the only way to know w/ the exception of seeing w/ your own eyes, is to completely research the engine that comes in a specific car and at the same time to be "SURE" that the engine in that car is for sure the original engine that came from the factory in that car. In the case of this L-81, I found the GM history of the LM-1 (ZDD designator) and also an article in Hot Rod magazine that gives the history of when the L30 was replaced w/ the LM-1 and the Lm-1 up to the present time.
If you check the engine designator on the Mfg. sheet from the '81 Vette, you'll see that it's ZDD which is the LM-1, the 4 bolt version of casting number 14010207.