WeasleVette454

I have a set of 3946074 aluminum heads that came extra with the WeasleVette this past winter. The http://www.mortec.com web site says that this casting was installed on the 1969 L88 and ZL1 and the 1971 LS6...both have a 118 cc chamber "round exhaust port".
My questions are...was there a valve size difference?...was there a spring(s) difference (mine has double valve springs)...and did the factory do any porting?
Since I have the original LS5 block, (the Mortec site says that the LS5 and LS6 share the same casting number block) and 074 heads, sounds like half the battle is won towards an LS6 specification build up.
Where may I find answers on the REAL build specs for these engines...L88, ZL1, LS6, that is.
Thanks!!
Weasle :D

Rowdy Rat

The 3946074 was an aluminum open chamber casting that was used in production applications on second design 1969 L-88 Corvettes, 1969 ZL-1 Corvettes and Camaros, and 1971 LS-6 Corvettes. There were no technical differences in any of these castings... They were identical for all practical purposes.

First design L-88s, and all L-89s used a closed chamber aluminum head (3904392 or 3919842 depending upon the model year) that was considerablly different than the "074" head.

Regards,

WeasleVette454

Thanks Rowdy...I have a friend of mine that is trying to talk me into getting rid of these 074 castings in favor of newer technology aluminum head. But these heads I already have are complete and look to be in very good shape. Key bit of info...they are paid for. I can't help but think that if they were good enough for the L88 or the ZL1, not that the LS6 was a slouch...they will be perfect for my "from LS5 to LS6 rebuild".
Thanks for your input. :cheers:
Weasle :D

Rowdy Rat

You're very welcome!

The "074" heads were state of the art when they made their debut in the late 1960s, but technology has passed them by to some degree. They are still a more than adequate cylinder head for performance applications and if they are complete, check out OK on pressure and zyglo tests, and are paid for to boot, I see no reason not to use them. You may lose some horsepower to today's current state of the art head, but I doubt you'll notice it much (if at all) on the street.

While many aftermarket manufacturers like to proclaim their parts as "new and improved", not all of them are... There's a lot to be said for the hours of testing and development that went (and still go) into GM designed and manufactured parts.

Good luck with your engine project!

Regards,


[Modified by Rowdy Rat, 11:33 PM 5/26/2002]