My 66 Toro has had the carb rebuilt by "Carb Re builders" in Oshawa and after some adjustments works well and responds as it should. Choke comes on and off as it should and all linkages and butterflies and secondaries also work as they should. Also no vacuum leaks.

The one problem that I still have is after I shut it down for maybe 1/2 and hr and certainly overnight it requires a lot of cranking to start her back up as if the fuel is draining back down the line. (I have checked and the bowl is empty). Carb does not leak and I have preformed the bench overnight leak down (for the well plugs) and paper is dry. I was told by my re builder that it is definitely evaporation due to percolation caused by the new (93 octane) fuel used today which is much lighter and prone to this issue.

I have a hard time accepting this and I am asking anyone if they have had this problem and what to do to overcome it. Re builder suggested blanking off heat tubes under carb?

 

Does the fuel filter have a functioning check valve?

I'm curious how you verified that the bowl is dry after half an hour? Did you use a gauge through the idle vent tube to check float level? Or are you simply looking at the accelerator pump shooters?

When you did the leakage test off the car, did the bowl empty during that test? If not, I can't see how bolting it to a car is any different.

How old is the fuel pump? Ethanol can cause the check valves in the pump to deteriorate, which severely reduces pumping efficiency.

 

Does the fuel filter have a functioning check valve?

I didn't know that the filter would have one. It is the sintered bronze type.

I'm curious how you verified that the bowl is dry after half an hour? Did you use a gauge through the idle vent tube to check float level? Or are you simply looking at the accelerator pump shooters?

Simply looking at the accelerator pump shooters.

When you did the leakage test off the car, did the bowl empty during that test? If not, I can't see how bolting it to a car is any different

No, I don't think so. It was a while ago, hard to remember if I even checked.
I was just interested in determining if the wells were leaking.

How old is the fuel pump? Ethanol can cause the check valves in the pump to deteriorate, which severely reduces pumping efficiency.

Fuel pump is new from "rock auto". No ethanol in our 93 Octane in Canada, so they tell me.

Just had a thought as I was answering your questions Joe. Could the fuel tank suck back the fuel from the bowl if it was not vented properly given that my fuel filter does not appear to have a check valve in it?

 

The fuel tank might suck fuel back, but I think a non-vented cap is more likely to cause fuel starvation problems towards the end of a long drive.