I have 4 Chevy Coupes. They all have W-1 Carburetors on them and all rebuilt by the same person. On three of the cars I can let set for close to month and can start them without priming them. On the fourth, if it sets for more than a couple of days it won't start without priming it. Is there anything I can do or should I get another Carb?

The earliest W-1 carbs have the problem described for the "fourth". The only fix is to lower the float or replace the carb with a later model. If they are all the same year then the casting may be from an earlier year and must be replaced if the float lowering does not solve the problem.

I only recently learned that there are numerous variations of W-1 carbs. I mistakenly put the right parts in the wrong carb...or vice versa...only to find later it was all wrong. Many of the parts are interchangable but not necessarily compatible. As an example, the wrong metering rods and jets may fit but may not be a 'match' for each other.
Best to first check all the parts as being right for your particular model W-1.

Coach,
The lesson you learned should be and example for many more people. In rebuilding carbs I often find parts from unknown carbs substituted for the correct ones. They or someone else thought that just putting in rebuild kit is all that is required. When it does not result in a correctly running carb that don't understand the problem. It is tough sometimes for professionals to get it right after someone has "worked" on a carb.

Then there are the folks that think that they can improve the performance by putting in some parts from another carb., larger jets, metering rods, etc. Or put a later model carb. on an engine and then wondering why the plugs foul faster. The engineers designed the engine, fuel system to be compatible. Changing one component most likely result in an imbalance.

Jonjet. I would suspect that the fuel pump may be weak on the engine thats needs priming.
I had that problem years ago with my '34....took the fuel pump apart and found a thread caught under the fuel inlet valve in the fuel pump - reducing it's fuel delivery at cranking speed.

hello master mechanic .. if ya got an old car and it cranks up really easy and when u put it in reverse . it seems to have tons up power & get up & go . but when you go forward up a slight incline there is very little power & no get up & go .. what could be the problem and what should i check for >??? thanx

Chance
Read my reply in the other section you posted this question.
Tony