1969 L-89 question

[Patrick B.]

The 074 open chamber aluminum heads were introduced on the ZL-1 in December 68 and replaced the 842 closed chamber heads on the L-88 around April 1969. Did the beginning of the 074 head mean the end of 842 head as a production part? Did the L-89 and closed chamber L-88 cease production when the stock of 842 heads produced prior to January 1969 dried up?

Does anyone have a 69 L-89 with 842 heads cast in calender year 1969?

I know that 842 heads were listed as service parts as late as the 1990's, but it is interesting that there were no 1970 Chevy big blocks with aluminum heads including the L-89 396 Camaros that would have used 842 heads. Even the only one planned for the 70 Corvette was the axed LS-7 that would have used the 074 heads.

[Mark D.]

Re: 1969 L-89 question

My car still retains its original March, 1969 842 heads.

[Wayne M.]

Re: 1969 L-89 question

Reading Roger Gibson's Sept. 1991 article in the Restorer, he says the L89 used the "842" closed chamber heads from 1968 thru to the end of 1969 production. But the 1969 L88 switched to the open chamber 3946074 head at its introduction in June of 1969. A different engine assy. code suffix was used for these late L88's.

Here's a pic of an early "842" set I have, showing casting dates.

[Patrick B.]

Re: 1969 L-89 question

My car still retains its original March, 1969 842 heads.

Mark-- Your heads certainly demonstrate that the 842 and 074 heads were being being made simultaneously for production which did not happen for successive casting numbers of iron heads. Since there where far fewer 69 L-89 Corvettes than 68's despite the much larger number of 69 cars, I thought that maybe the option ended before the end of the model year. Do you know of later 69 L-89s than yours?

[Mark D.]

Re: 1969 L-89 question

We know the cast iron heads, used for 1969 L71, were most likely cast as late as June, or even July, 1969. I have always been under the impression 074 heads came into production in January, 1969 in the ZL1 Camaro. They started showing up in L88 equipped cars (LO) post strike 1969.

It's an excellent question regarding when did 842 production end. My March 842's are dated differently than Wayne's in that the date is cast inside the runner so, it can't be read with the intake manifold in place. It would be good to hear from others because (I think) we know there are no documented L89's with the open chamber design and I would bet the 842 head production stopped prior to model year end with surplus entering service.

[Patrick B.]

Re: 1969 L-89 question

We know the cast iron heads, used for 1969 L71, were most likely cast as late as June, or even July, 1969. I have always been under the impression 074 heads came into production in January, 1969 in the ZL1 Camaro. They started showing up in L88 equipped cars (LO) post strike 1969.

It's an excellent question regarding when did 842 production end. My March 842's are dated differently than Wayne's in that the date is cast inside the runner so, it can't be read with the intake manifold in place. It would be good to hear from others because (I think) we know there are no documented L89's with the open chamber design and I would bet the 842 head production stopped prior to model year end with surplus entering service.

I have a ZL-1 engine from a Camaro that has 074 heads cast in DEC 68. That's why I assumed Dec 68 as the beginning of production for 074 heads. Neither TRW nor GM ever had a piston I know of that would give 11:1 compression with 074 heads so I think an L-89 would have been impossible with 074 heads unless there were some very rare pistons. The end of 840 iron head production did not end the L-71. I'm sure late 69 engines used 291 heads which were almost identical.

[Dick W.]

Re: 1969 L-89 question

I have seen a couple cast Dec '68. Hinckley can verify, but think the ZL-1 engine production actually started late Dec '68., for the Camaro at least. I think Corvette started installing open chamber engines in March, and were mixed in with the close chamber engines until about June or so. The last in, first out concept would explain the mixing. The last IT engine was shoved back into the corner and until all the engines in front, or they got a memo to clean out stock, it stayed there

[Mark D.]

Re: 1969 L-89 question

I'm sure late 69 engines used 291 heads which were almost identical.

i agree 100% AND I'm sure sure your correct in 074 application date, as well.