That’s interesting Brice, I thought about the possibility of cork over fiber, the later of which I’ve tried with no success. On one carburetor, I machined the gasket surface of the bowl flat in my mill, I took off about .025” before it cleaned up. On the air horn, I heat treated, i.e., soaked it at 400° for a couple of hours while it was clamped to a 1” thick flat tooling plate. This does flatten the gasket surface out but caused a little drag in the choke shaft and I had to hone a few tenths out of the power piston well apparently because of the casting relaxing or stresses being relieved. I’ve tried heat treating both the bowl and the air horn on other carbs and had the same trouble with leakage.
For the thick fiber gasket, I did the same as you did on the cork. I traced a .042” (nominal 1/16”) thick fiber gasket from the original gasket and spent an hour meticulously cutting it with an Exacto knife, pinching the holes with gasket punches.
I still had leakage into the Venturi (lo pressure areas) and some weeping around the out side. This type of gasket material gets almost no compression from the four feeble #10-32 screws that hold it together. The later “B” carbs use #12 screws (still only four) and have a thicker edge on the airhorn than the early ones, probably an attempt to stiffen up the gasket surface because of so many dealer comebacks. If you tighten it too much it will warp the airhorn again at the hole bosses.
As you observed, the cork should compress a little more than the fiber. However, the first problem that pops into mind is how narrow the thin webs could be cut in cork. That’s the problem with cork being used in such a thin cross section since it is made up of such course material. Even VC and pan gaskets are quite fragile. I have some Victor cork gasket material in 1/32” and 1/16” that is made up of fine pieces and is suspended in a black binder so it appears much darker than cork usually is. Is this the type of material that your referring to??
I’ve never seen cork that was labeled “gas grade”. The cork that I’ve found at the local FLAPS, Farm & Fleet and hardware stores all seem to say that they are meant for application with oil, i.e., VC, oil pans or timing covers. Do you recall if the material had a manufacturer’s label on it, or was the auto parts store one of the larger chains??
After months and months of searching and questions I’m still wondering how all the vendors can list “rebuilt Rochester “B” carbs” in their catalogs. Maybe their rebuilders have found some magic formula to seal them up cuz if you just clean them and put a kit in them all most all of them are going to leak. I would be willing to bet that the vast majority of the cores that are sent to them are rejected because of warped castings and of course at the customers expense, meaning that your paying shipping out and back for each rejection.
If your idle mixture adjustment does not stall the engine when it is seated them fuel being sucked into the Venturi through the gasket is what is keeping the engine running. It will most likely seem to run pretty good like this but your low fuel mileage will tell the tale.
Denny Graham
Sandwich, IL
