RX-7 Carb Return Line

[tom_sprecher]

Why does my 1G have a return line off the carb? Why does the return have a one-way check valve inline?

[Kubotawally]

The return line is to vent vapor and acumulated fuel back to the tank. It's actually a function of the 70's mandated smog equipment. The one way check valve is a safety device incase of rollover. On my IT can I've converted to a single line

[joeg]

A return line is not necessarily a bad thing. It can also help reduce vapor lock.

[ddewhurst]

Just to add a bit more about the return line for the 1st gen RX-7. It is my understanding that the return line has to do with the OEM fuel pump. The OEM fuel pump when in good working condition always pumps the same psi with more pressure than is required at the carb. Excess fuel returns to the tank. As the motor is run at higher rpm's more fuel is used & less fuel returns to the fuel tank. The OEM charcoal canister stores gas tank and carb fumes when motor stops & is vented to atmosphere.

Tom, if your 1st gen RX-7 has a return line with the OEM carb or a blueprinted carb leave the return line in place. Some people who blueprint carbs use the return line & some don't use the return line.

[tom_sprecher]

My information indicates the carb is a Paul Yaw unit and after reading the info on his web site he wants to see 2-3 psi and a return line. It's already there so I guess I'll keep it. Anyb0dy know where to get a 0-5 psi gauge? I've tried MSC and internet with no luck.

After questioning the need for the check valve in the return line one buddy said it may be necessary to prevent back pressuring the carb and regulator as the fuel heats up during the day. I mean 2psi ain't a whole lot of pressure.

Anybody got any ideas at to what is in the picture of my other post?

Thanks,

[benracin]

Got my fuel pressure gauge here, and it's awesome. Sorry I can't tell you which model or where it's at, but I do know it came from this place. There's a 0-5 psi and it's awesome accurate.

http://www.mcmaster.com/

[lateapex911]

Paul sold me mine, it's "Yaw calibrated" LOL.

[ddewhurst]

Tom, the key to a great fuel gauge is the accuracy/repeatability of the gauge. The 0 to 5 psi gauge accuracy I use is plus/minus 1.5 % of the full gauge. That would be plus/minus .07 psi.

Try McMaster-Carr part number 4026K27 It's about $40.00 with shipping.

Dewhurst calibrated.......... ;)

[tom_sprecher]

Thanks for the replies. Since McMaster has a warehouse here in Atlanta and the weather couldn't be more perfect I'll cruise the Harley over tomorrow and pick up one of those gauges.

Hope to see some of you guys at the ARRC.