The difference in thickness is really quite large...
Red-ish NOS ones - 0.0215" (about 22 thou on average)
Blue gray ones - 0.065"
About 3 times thicker!


Exactly the issue I had the first time I tried to refit the manifold on Binny.
I think the thicker gaskets can also prevent the O ring between the head and the manifold getting sufficient clamp to stop the front waterway leaking into no #1 inlet.xvivalve wrote: ↑Sun Jul 08, 2018 10:33 pm Both 1850 and Sprint inlets have in my opinion a missing bolt; ideally they both need another in the bottom right corner to effect a good seal to the water jacket. My thinking is a thicker gasket is able to be compressed by the bolts and should therefore be a better option...EXCEPT in the bottom right hand corner where the missing bolt cannot do its job. A thinner gasket has less compressibility and therefore the manifold gets a more even interface with the head and no leak.