1964-1967 (and later) Corvette Exhaust Manifold Washers/Spacers

If you have a 1964 or newer Corvette (or a Camaro, Chevelle, El Camino, Nova, etc.) then you should know that GM used a unique, thick, flat washer (more correctly called a spacer due to its unusually large thickness) under eight of the twelve exhaust manifold bolts on all V8 small block engines (I haven't yet researched big block engine applications). All of the Corvette catalog companies sell a reproduction washer, but that repro washer is incorrect in one or more ways. The outer diameter of the repro washer is too large, the thickness is too small, or they are zinc plated, or they are made from stainless steel. This is yet another case where the reproduction part is obviously wrong. Note that the washers I have are not GM 3754153, which were used up through 1963. The 3754153 washer is also incorrect for 1964 and newer engines since it is too large compared to the smaller diameter washers used starting in 1964. The photo below shows an incorrect washer at the top left, and the correct washer at the top right. The bottom part of the photo shows that the incorrect washer, which is too large, is more obviously incorrect when the washer is seen sitting under the head of an exhaust bolt. Note how much incorrect washer is visible surrounding the bolt head. Compare that with the correct washer on the right. The correct washer is barely visible past the points of the bolt head. A judge can easily spot that difference and once they do, they take a deduct. You can avoid that deduct with these correct washers. I have a very limited supply of these washers. These washers have the correct thickness (0.127 inches), correct outer diameter (0.683 inches), and have the correct heat treated, unplated finish (note that the spacers look quite a bit lighter in the image below than in real life due to the camera flash I used for the photo). Note that these washers were only used under the front-most two and rear-most two exhaust bolts on both LH and RH sides. Thus, a total of eight washers are needed for a car. Note that if you use incorrect washers that are too thin then the outer exhaust bolts can bottom out and not provide the necessary clamping force to prevent an exhaust leak between the manifold and the head.

The cost of a set of eight spacers is $24, plus $5.50 for USPS postage.