holley fuel return question

[tflyboy77]

I have a Holley 4150 pro systems carb and I'm having trouble with fuel boiling at cruise speeds. Now this is a trans am so I can't run any more carb spacers. I have insulated the fuel lines front to back. I know that the fuel lines are cool but when it sets in the bowls it gets hot and boils. Any suggestions would be great.
The second part of this question is that if I put a return line in the fuel rail back to the tank that would cool the fuel in the lines. Has anyone ever installed the return out the other side of the carb? Fuel in one side of the bowl and return out the other side. Just an idea! Let me know what you think.

[SkinsandJrfan]

From what I have been told its due to ethanol gas. That and carbs don't mix well. It caused vapor lock. Try finding gas without ethanol. I live in north carolina and can find them at times but it's tough. I know this is no help but that's what a well respected carb guy in mr area tells me.

[Chevelle598bb]

You can go in one side of the bowl and then return out the other side. You will never fill the bowl that way. The proper way to run a return is a dynamic bypass regulator. You run the feed line to the fuel log at the carb. On the out going side of the fuel log you place your regulator (in side of regulator). Then run your return line from the return side of the regulator back to the tank. You will have rock steady fuel pressures at all rpm ranges unlike dead head systems and the unused fuel is returned directly back to the tank which keeps the fuel cooler. It also will make your fuel pump last much longer since it is pumping in a closed loop system instead of always against the regulator. I live in Texas and in 110 degree heat with my old 600 hp big block I never had fuel boiling issues with ethanol enriched gasoline. I also had a very good cooling system that kept temps right under 200 degrees.

What year trans am are you working with.

[tflyboy77]

I have a 77 T/A with a Pontiac 468 stroker. I just got back from the Motor State Challenge which was more fun than should be aloud. I kept having this problem when cruising and no prob at all when beating on it.

[Chevelle598bb]

Are you using a mechanical fuel pump?

[tflyboy77]

Yes I am using a mechanical pump and a factory tank.

[tflyboy77]

So can I go through the bowls and then use a regulator. I know the standard way to do it is before the bowls in the fuel log.

[Chevelle598bb]

No you can't go through the bowls.

It must be part of a fuel log.

[TheJDMan]

Take a look a this, may help.

https://www.pro-touring.com/showthre...ol-Carb-works!

[Chevelle598bb]

Here is a photo of my car when it was a drag car with a big block Chevy. The line going to the back of the carb is the pressure line. Then the fuel goes to the carb and out the front of the fuel log to the regulator. From the regulator it goes out the bottom into the return line which was the same size as the feed -8 an.

For some reason it is the iPhone app is not allowing me to post pictures here is a link below.

https://www.pro-touring.com/attachment.php?api=1&attachmentid=53363&d=13257218 54

[tflyboy77]

Great suggestions. I'm going to look into that plate/spacer. My big concern is that with the shaker I can't lift the carb much at all. As for the return line, I'm going to put it in the log with a regulator and see if that does the trick. Which dynamic regulator are you guys using? There's a few out there that are very different prices.

[Chevelle598bb]

I used a Barry grant but it is not produced anymore. Aeromotive makes a three port regulator that is very similar for about 80 bucks or so.

[tflyboy77]

Thanks guys, I'm going to dive into it this weekend. I'll let you know how it goes.

[tflyboy77]

Well I got the return line plumbed and the cruising issues are resolved. However the return line did not stop it from boiling the fuel while parked. If I get the car hot and then stop for 30 min, it is near impossible to get started because of flooding. Any other time you can just hit the key and go.

[Chevelle598bb]

So after it sits (hot) the fuel drains out of the bowl flooding the engine?

[tflyboy77]

The fuel boils out of the bowl!

[tflyboy77]

You have to sit there cranking with the throttle wide open until it fires, then you have to play with it to keep it running until the bowls fill. After all of that it's fine until you shut it off again.

[tflyboy77]

I'm getting ready to order the carb cool and see if it will fit under the shaker.

[Randy67]

This starting tip from The Carburetor Shop: http://www.thecarburetorshop.com/Tro...m#Hardstarthot
helped with a similar problem on my Camaro autox car. The crossover headers (they are wrapped) create a lot of heat and cause carb fuel issues. Basically what I do (from their tip) is to start cranking for a few seconds to clear the fuel, turn on the ignition (this part is hard to do with street cars) and then start opening the throttle to about 1/3. It fires up every time now.