69 L-89 heads 842/074?

[Glenn454]

Which heads were used on the late production 69 l-89 corvette. 22,000 and above. My Dobbins fact book says the 074 open chamber head was used after 22,000 serial. The black book and others say the 842 was used. Does any body have some info on this. Thanks

[JohnZ]

The NCRS spec guide says they used 842's for L-89's, and the 074's were used for L-88/ZL-1. Try posting over on the NCRS Tech Board - several extremely knowledgeable guys over there on this issue.

[Rowdy Rat]

Originally Posted by Glenn454

Which heads were used on the late production 69 l-89 corvette.

Glenn,

All 1968-1970 L-89 applications (Corvette, Camaro, and Chevelle) used the "842" closed chamber head. There are differences in the core plugs used on early/late 842 heads... If you have a car built after May 1969, look for a casting with one core plug... Prior to that, two plugs are more typical (but not exclusively so).

22,000 and above. My Dobbins fact book says the 074 open chamber head was used after 22,000 serial. The black book and others say the 842 was used. Does any body have some info on this.

The reference in the Black Book concerns 1969 L-88s... First designe L-88s (to about #22,000 - "IT" broadcast code) used the 842 closed chamber head, while second design L-88s (a group of early cars and those after #22,000 - "LO" or "LV" broadcast code) used the 074 open chamber head. All ZL-1s in 1969 used the 074 head.

Regards,

[Glenn454]

Thanks for the replys.. Iv'e seen the same info. But iv'e
talked to a guy with a 69 l89 tri power, his car was a aug or a july car that had 074 heads on it. In the back of the dobbins book in the head section he has the 074 on the later l89s and the 842 on the early cars. Maybe the ncrs
guys might know.

Thanks

[Rowdy Rat]

Originally Posted by Glenn454

Thanks for the replys.. Iv'e seen the same info.

You're welcome Glenn.

But iv'e talked to a guy with a 69 l89 tri power, his car was a aug or a july car that had 074 heads on it.

If this car did have 074 heads on it, you can bet the farm that they were installed after the fact. My former July built 1969 L-89 had 842 heads as have the twenty or so L-89 cars that I have in my survey built after that... This includes a couple of December built L-89 Corvettes and a few 1970 Chevelle L-89s that I've seen as well (all built during the 1969 calendar year) also used the 842.

Because using the 074 head would have required a brand new piston (which GM didn't have at the time) to achieve 11 to 1 compression, this application is pretty straight forward... No 074s on L-89 cars.

In the back of the dobbins book in the head section he has the 074 on the later l89s and the 842 on the early cars.

I have been told that Dr. Dobbins used to put information into his books that may not be completely accurate (done basically to trip up people trying to create rare cars)... This may be an instance of this misinformation or it could be something as simple as a typographical error.

In any case, 074 usage on production cars is limited to second design 1969 L-88 Corvettes, 1969 ZL-1 Camaros and Corvettes, and 1971 LS-6 Corvettes. Any other aluminum head big block application from 1968 forward would have used the 842. 1967 big block aluminum head usage for all applications (L-88s and L-89s) would have used the 392 head.

Maybe the ncrs guys might know.

Never hurts to back up your sources... You can never have too much documentation or too much proof. Just be aware that there are many NCRS guys posting on this forum as well as www.ncrs.org.

Some of us just like a little change of scenery from time to time.

Regards,

Stan Falenski

[Glenn454]

Thanks for clearing that up for me.. The piston issue makes since. I didn't know that about the dobbins book.

Thanks