Mighty Mouse

Hey Guys,
I'm a C3er and don't usually spend much time over here. Although I used to have a 63 coupe. Anyway my ? is how much would a set of 9 fin valve covers that say Corvette on them be worth? THey are in great shape just need some minor cleaning. What I find on the Web is "In 1956 the optional engines had 9 fins on the valve covers. The 9 fin covers would be gradually phased out in 1957 and by 1958 all fined covers had only 7 fins. " Would this be true. I have a chance to buy these cheap but can't use them on my C3, but I think I will pick them up anyway. THanks :p:

JohnZ

There were three different types of 9-fin valve covers, and all had the same casting numbers; here's how to tell the correct application for the three versions:

1. Early '56 - straight upper flanges, no clearance notches for intake runners.

2. Late '56 - clearance notches in upper flanges added for 2nd design intake with larger intake runners, continued into '57; was used on '57 fuelies until S/N 1900, and on '57 2x4's until about S/N 3900, when the new 7-fin cover started to show up; from 3900-4500, both 7-fin and 9-fin covers were used (in pairs) on 2x4's, and from about 4500 on, 2x4's used only the new 7-fin cover.

3. '57 fuelies after S/N 1900 - middle portion of the top rib milled out to clear the air meter; fuelies after about S/N 2900 used the new 7-fin cover.

All these covers had the .030" "low script" Corvette name (the change to the .125" high script occurred on 1958 models about S/N 3600).

Vetterodder

John, didn't those early valve covers have a different bolt pattern than later ones?

Corvette Cowboy

Sometime in early '59 the valve covers changed the bolt pattern from the upper bolt holes being slightly inboard of the lower holes, to the holes being directly opposite each other. I don't know exactly when the change was made other than early '59s had the '58 style covers.

DZAUTO

To buy a set of 9 fins can be kind of expensive. THEY WILL ONLY FIT MID 59 AND EARLIER HEADS, because of the staggered bolt pattern,sort of. The bolt holes on the intake side of the head are in the same position on all heads. The holes on the exhaust side are the ones which are in a different position. I have a SB400 with 66 2.02 heads on it and 9 fin valve covers in my 56 Vette. When I had the engine in the machine shop, I had the machinist weld (he can plasma spray weld cast iron) additional bosses and then drill/tap them for a staggered bolt pattern on the ex side of the head. Now those heads have a dual bolt pattern and I have a big displacement engine which sort of looks like an early engine.


[Modified by DZAUTO, 8:22 AM 5/12/2002]

JohnZ

The change from "staggered" holes to "straight" holes occurred during March, 1959, about S/N 6000, when the heads changed. This was the first time the number changed (to 3767493) since the original 3726086 cover was released for 1956 production.