Going through a carb rebuild and was wondering what the factory used for the carb filter. I know the correct filter was the paper filer, but they made one with and without a built in check valve. One of the carb tuning papers actually suggests to use a filter with a check valve to keep the gas from running back into the tank after the car sits for a few days. I'm sure most of you experience hard starting after the car sits for a few days. The fuel pump has a check valve as well, but it may not be enough. Just wondering if the GM engineers covered that back then. The check valve in the fuel filter is suppose to keep fuel from running through the lines, keep it in the carb for easier starting. Napa part Fl 3051.
when rebuilding or doing tune-ups I always use the filter with the check valve, I have seen the problem with the gas draining back like you said many times, the check valve helps
When the car is daily driven, there shouldn't be much of an issue, but as most of us rarely fire the engine on a daily basis, the fuel will evaporate through the bowl vent and drain back out of the carb. as well.
Even with the "check valve" type filter, I doubt it does much good after sitting for a week or two. Can't hurt anything having a filter with it. The only reason I've seen them removed or filters used without the check valve is on high performance applications where the carb. bowl was being emptied out under heavy throttle. The check valve is a restriction in the fuel system.
Also, the inlet needle rubber pintle gets worn and can allow fuel to empty back out.
I try to fire the engine at least once a month, and never have to crank more than 5-6 seconds before it fires. Filter with a check valve installed.
When I drive the car regularly, as mentioned, there is no issue. Fuel is ready on start. But after 2-3 days it needs to crank a bit and that is with a newer fuel pump and check valve. To avoid that I keep a small squirt bottle with Truefuel (no ethanol) in it in the garage. I give the carb a squirt and it start almost instantly. Saves the cranking.
Thanks, just ordered a few filters with check valve. Reading the infamous "Lars's" tuning paper, he also suggests to remove the clip from the needle so the rubber needle tip can seal off the hole preventing fuel to drain back...I'll do the filter first, see what happens. Also try to remember to depress the gas pedal 2-4 times to get some fuel in the carb prior to starting.
Yes, the clip on the fuel inlet needle is not needed per Cliff Ruggles as well. Also, make sure it's pointy and sharp (the rubber portion) like a needle and not rounded (worn out). Speaking of pumping the gas pedal, make sure your choke is adjusted properly, that will effect cranking time as well.
