I was at a swap meet today. I seen several sets of Corvette valve covers, some had staggerd mounting holes, and some had non staggered, some were 7 fin and some were 9 fin. Were there different valve covers for different engines or years or ? ? ?

 

I think beginning in late 59 the holes in the valve covers went with the straight bolt pattern instead of the offset. Not sure on the fin count. Seen both, but never knew when the break offs were on the use. I think the 9 fins were 56-57. I think the fuel injected cars had one of the fins cut down for air cleaner clearance.

 

Yep, early V8 heads used staggared valve covers, and then moved into the 7 fin straight-across holes.

In mid 1966 production the mold for the valve covers cracked, and as a result all 7 fin straight-across valve covers made during and after 1966 production have a seam through the "o" in Corvette.

 

hello,
only 1957 fi cars had the top notch cut out for the air-cleaner, 3 different 7 fin covers with the same part number could be found on earlier corvettes with the staggered mounting holes...the differences were in the script heights ect.
seam lines appeared and if i am not mistaken also had the script lester on the underside.
regards , xiaoman

 

From my "Tech Bench" column in the May, 2004 issue of "Corvette Enthusiast" magazine:


Although Corvette aluminum valve covers look pretty much the same to the untrained eye, there were actually six different variations of them used from 1956-1967.

1. 1956 2x4 engines used P/N 3726086: (9) fins, low (.030”) script, staggered bolt holes, and no notches in the upper seal flange.

2. Later 1956 2x4 engines with a revised intake manifold having larger runners required two cutouts to be added to the upper seal flange to clear the larger intake runners, starting about S/N 1650 (650th car built). There was no part number change, and these covers carried into ’57 production.

3. When fuel injection was introduced in 1957, an interference was found between the air meter and the upper fin on the valve cover, and the middle area of the top fin was milled off on fuel injection engines, starting about S/N 1900. 2x4 engines continued to use the “un-milled” 9-fin valve cover. Again, no part number change.

4. A new 7-fin cover (essentially the 9-fin cover with the top and bottom fins removed from the mold) was introduced on ’57 fuel injection engines about S/N 2900. The 2x4 engines continued to use the original 9-fin cover until about S/N 3900, when the transition began to the new 7-fin cover already in use on fuel injection engines. From S/N 3900 to about S/N 4500, 2x4 engines used both 9-fin and 7-fin covers, and 2x4 engines after about S/N 4500 all used the new 7-fin cover.

5. The new 7-fin low-script staggered-hole valve cover continued into 1958 production until about S/N 3600, when the molds were changed to increase the height of the “Corvette” script from .030” to .125” to improve their appearance. This cover (no part number change) continued into 1959 production until late March, 1959, when the cylinder heads changed.

6. The two lower valve cover attaching holes (and the bolt holes in the cylinder heads) were re-spaced inward to match the location of the upper two holes in late March, 1959; this new “parallel-hole” 7-fin high-script valve cover, P/N 3767493, continued in production through the end of the 1967 model year.

 

john,
great info. i knew i read it somewhere (LOL).......we can always count on you for the minutiae.
regards , xiaoman

 

John:

I currently have a 63 Impala 283 in my 59. My build date is March 26 1959, should I have the straight or staggered hole heads? I thought I read in Nolan's book that there was somewhat of an over lap in heads in March, April and May of 59.
Steve

 

The NCRS '58-'60 Judging Guide should have information on when the change occurred and what range of overlap has been observed.

 

I love the look of these valve covers, but what about breather holes ?
I'd like to get a set for my 350 crate motor.