R-1 fuel pump vent

[maxpower1954]

When I bought my 64 R-1 Avanti back in 1993, it had a converted throw away Airtex Mopar fuel pump. It finally failed back in 2003, so I replaced it with a spare original Carter R-2 pump (I have a R-2 GT.) I plugged the s/c reference fitting with a brass plug. Been working just fine for 8,000 miles.

But since I've never had a real R-1 pump, I didn't know about the vent hole it's supposed to have. What's the purpose of the vent? The only thing I can think of is to prevent crankcase blow-by pressure on the rubber diaphram, which might affect pump fuel output volume. Does anybody know for sure? Russ Farris

[Mike]

To the extent that the oil seal on the stem works, the area behind the diaphragm is a sealed chamber; unless one of the two venting options is open. It would act like a soft spring, deforming the diphragm; and probably reducing fuel flow. I suppose it would also alternate blowing air into the crankcase and drawing oil out, past the seal.
The R1 pumps vented through the little "tower" on top of the pump. R2 pumps have the tower, too. The passage isn't drilled all the way to the top. It's only started, inside. Likewise, R1 pumps have the boss for the supercharger boost referance cast in, but not drilled.

[maxpower1954]

I had forgotten about the rubber seal Mike, and I just re-built my GT's R-2 fuel pump a month ago! Senilty can't be too far behind...

So if I came up with a vent arrangement at the s/c boss like the one in the re-building thread, that should work. I have never experienced any problems with it six years and 8,000 miles, though. Maybe I should spilt the case just to check out the diaphram. Russ Farris