Re: ZL-1 & L-88 head design clarification
 

I think the open chamber iron heads are #990.

Re: ZL-1 & L-88 head design clarification
 

These '69 cast iron L-88 heads...I picturing them to be very similar to the ZLX head - open chamber cast iron...

Re: ZL-1 & L-88 head design clarification
 

I see we are talking about 69 version heads. They are 990s.


Jason

Re: ZL-1 & L-88 head design clarification
 

[ QUOTE ]
Here is the casting mark.

[/ QUOTE ]

Andy,

Where exactly is the "half moon" casting mark on the head?
Front/rear face?
STeve

Re: ZL-1 & L-88 head design clarification
 

Rich, I believe the last LS-6 Corvettes produced in -71 got the first open chamber iron heads, similar to the #074 aluminum head.

Re: ZL-1 & L-88 head design clarification
 

All Chevy casting marks are on the front face of the head.

Re: ZL-1 & L-88 head design clarification
 

Closer view.

Re: ZL-1 & L-88 head design clarification
 

That rectangular port/open chamber #990 cylinder head was not around in 1969 or 70. That and the similar #188 are what came on the newer crate LS-6's and LS-7's. I've seen reference to this so-called cast iron ZL/X head and would like to know what the casting number is. The earliest cast iron rect. port/open chamber head I know about and have owned were 1971 dated #026. They are also listed in Colvin's book as standard issue for the 1971 LS-6 Chevelle. A car that never happened so they must have been over the counter service pieces. The 1971 Corvette LS-6 all used the aluminum rect. port/open chamber head #074, the same as found on the 1969 L-88 and ZL-1 Corvette.

Re: ZL-1 & L-88 head design clarification
 

According to Colvin, there were 3 #'s starting in '67 that had this "half moon" casting mark, all square port, hi perf applications. (Mechanical lifters).
The first was '67 only, #3904391, and had no temp sending unit.
The 2nd was the #840, and was installed in '67, '68, and '69. It was also cast in '69 as a #291, with a tapered spark plug seat. The #291 was also used in '70, since the 512 block was used in '70 for the 454. The only difference was the crank being stroked for the extra cubes.
The '67 L88/9 aluminum heads (#392) was identical to the #840, except for the casting metal.

Re: ZL-1 & L-88 head design clarification
 

[ QUOTE ]
According to Colvin, there were 3 #'s starting in '67 that had this "half moon" casting mark, all square port, hi perf applications. (Mechanical lifters).
The first was '67 only, #3904391, and had no temp sending unit.

The 2nd was the #840, and was installed in '67, '68, and '69. It was also cast in '69 as a #291, with a tapered spark plug seat. The #291 was also used in '70, since the 512 block was used in '70 for the 454. The only difference was the crank being stroked for the extra cubes.
The '67 L88/9 aluminum heads (#392) was identical to the #840, except for the casting metal.

[/ QUOTE ]

So, the #3904391 is the '67 L-88 head then? Did I read
that correctly, or read something into that? https://www.yenko.net/ubbthreads/imag...lins/dunno.gif

Steve