Stock Rx2 fuel lines
 

So I'm just testing to see if my regulator is no good, as well as running the fuel system dead headed is also a factor. I'm testing to see if this Mallory 4309 running a return line will fix my fuel problem.

So, there are a few lines coming from the tank that lead into the engine bay coming up next to the brake booster. I know which is my fuel feed. But which one can I use temporarily as a return to test my regulator?

If this solves my problem, I will be putting all new braided lines and possibly a fuel cell. As well as swapping from the Holley Red pump to Mallory 140.

The Mallory 4309 is supposed to have a 3/8" return line according to the instructions. When I hooked mine up to a 3/8" line under my car that leads back to the tank, it fixed all of my fuel line related flooding problems.

The instructions say to use a 5/16" send line so your stock 5/16" send line can stay. Or if you've upgraded it to 3/8" you will need to downsize it to 5/16".

This is what works on my setup.

What pump are you running and is this on your blow through set up?

This will be a blow through set up as well. But with a Weber.

Yes, blow through. The carb is a Nikki with its stock return line blocked. The only line that goes back to the tank is from the "bypass" fitting on the bottom of the mallory 4309.

The fuel pump is what was recommended to me. It is an MSD 2225 and has no problems getting down to 2.5psi for the Nikki. It also just happens to have a 3/8" inlet which is helpful and a 5/16" outlet. The outlet is perfect for my stock send hardline under the car.

Good luck with the weber. j9fd3s and I figured out why some many people have problems with these carbs on rotaries and boost. It is because of only having 2bbls. It is either too rich in vacuum and just right in boost, or the other way around. You can't have it both ways on a 2bbl like you can with a 4bbl carb with boost and the wide rev range of a rotary.

I hope to be able to tune the Weber so it drives nicely in vacuum and is slightly lean in boost. I am going to be injecting methanol to make up for this problem.

Thanks for the tips on the fuel lines. I was going to to -6 feed and -8 return. Which would be oversized from what is working for you. I have just always run those sizes for my fuel injeced set ups.



Edit: -5 AN (5/16" equivalent) fittings are rare and almost impossible to find the right ones. Since I am doing my entire system in AN fittings, I'll be using -6 feed and return. Should not effect the outcome. We'll see anyways...