Hi,

I just got done with my tpi to carb swap and I have a 255lph in tank pump with a Holley billet regulator. The regulator can only regulate down to 7psi. Can I run a deadhead regulator after the bypass regulator? Will it hurt the pump at all?

 

If you can't get it to regulate down past 7psi, it could be an issue with the return line. I have the aeromotive regulator on my car and had a similar situation. I had to fix some kinks in the return line to get things sorted out.

 

I can check the return line but there is no issue to my knowledge. Do you have a 255lph pump? what can you put your pressure down to?

 

I do have a Walboro 255 pump and I have my pressure set at 5.5 psi. I never tried to take it lower than that, but I think it would go lower if I tried.

 

Which regulator do you have? Maybe the regulator isn't a good one. I might have to switch to an aeromotive

 

I have used the very affordable Mallory 4309 regulator on multiple EFI-to-carb swaps over the years. Never a problem. Including applications where the fuel pump has been upgraded to a Walbro 255. If you can't get pressure low enough with that regulator, you have a restriction in the return line, in all likelihood.

[edit] Mallory/MSD changed the part number. And doubled the price. Don't believe me? Here they are on Summit, both old (4309) and new (29387) part numbers:

4309 (old part number, no longer available, but you'll have to trust me, it used to be about $60):

https://www.summitracing.com/parts/maa-4309

And now the new part number for the exact same regulator at $120 each:

https://www.summitracing.com/parts/msd-29387

 

Check out this page on running a static regulator after the return regulator.

http://www.aeromotiveinc.com/tech-he...ed-regulators/

Also, even with the Walbro pump, getting pressure down shouldn't be a problem (I would think). Mallory lists their regulator as being able to handle 200 GPH which is far more than the Walbro pump puts out.

I would agree with the other poster about checking out the return system first before adding a second regulator, but this page does say that a second regulator can overcome a poor return system.

Hope this helps

 

Thanks, the aeromotive page is where I got my idea.

An update. I looked for kinks and there are none. But I found out when the car is not running the regulator won't go less than 7psi. I was messing with the regulator and loosened it quite a bit and I started the car and it was running strange and I noticed the pressure was 4.5psi. So it turns out when it's running I have full adjustment range from 4.5 to 9 psi.
Is this a normal thing?