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Index > Engine/Drivetrain > Thread: Vent lines with Weber carb conversion
Thread: Vent lines with Weber carb conversion

Posts: 3
posted August 08, 2020 08:23 PM

Vent lines with Weber carb conversion

I've got a REPU with a S5 engine that I'm installing a DCOE Weber onto, and am starting to clean up all the stuff the aftermarket carb doesn't use. I've already plugged the fuel return line, but there's one last fuel hose coming up the middle of the firewall which I'm pretty sure is the fuel tank vent line. What are yall doing with this line when converting to aftermarket carbs? Does it just stay open to vent? Put a little filter on it? Route it to the carb filter plate?

There are also two lines coming off the oil filler neck that I know need to go somewhere. Can all three of these be T'ed together and run into the carb filter plate or oil catch can or something? I assume T'ing a fuel vapor line with crank ventilation lines would not be ideal, but I don't know.

​​​Hit me with some wisdom, please.

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Posts: 1672
posted August 24, 2020 04:17 PM

I use the return line, it allows fresh cold fuel from the tank up to the carb, and my fuel pumps seem to last longer with a return line and not dead headed.

The gas tank needs to vent one way or another otherwise it would pull a vacuum when fuel leaves the tank and that space in the tank is not replaced with air. Also when the truck is parked outside in the heat, the gast tank will heat up and fumes want to exit or the tank gets pressurized.

At least put a filter of some sort on it if not run a line to under the air filter.

As for crankcase ventilation, at a minimum put a little filter on one of those ports. Better yet run a line to under the air filter again. There's a good thread on using both ports as a system if you search rx7club.com for 'yellow mustard' or 'lung butter'. Since that's what accumulates under the oil filler cap w/o proper crankcase venting.

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