Fuel filter(s) and vapor separator questions 70 440 6bbl

[biomedtechguy]

So I have a WIX metal fuel filter at the end of the hard line that comes from the gas tank, then the mechanical fuel pump, which is the Carter M6903, and then a metal reusable 40 micron low restriction inline filter that is part of the Promax lower fuel line, and then the 3 lines to the carbs.
I was just reading the 6 pack Engines book by Larry Shepard and he suggests the fuel filter go between the pump and carbs. I'm pretty sure the WIX filter at the end of the hard line is the stock filter location.
Either way I'm covered, but feedback is welcome.
Next is the fuel vapor separator. When I installed the Promax lines, I had to plug the vapor separator return line to the tank because I couldn't integrate it with the new lines. The vapor separator has been removed from the system.
Is that ok?

 

[dadsbee]

Filter never went before the pump.. always after. Even the vapour separator in stock "return line" form goes after the pump.

 

[biomedtechguy]

Filter never went before the pump.. always after. Even the vapour separator in stock "return line" form goes after the pump.

Yes, re: vapor separator/filter combo unit. What I mean by that is I think there is a screen filter in the vapor separator.
What about debris entering the fuel pump? The tank sock should keep chunks out, and I'm not "arguing" just concerned.
I'm going to look at my 70 chassis service manual.

 

[themechanic]

It isn't a bad idea to install a filter between the tank and pump. I had to on the 70 Cuda as it still has the original tank ad fuel lines and the fuel coming out does not look too pure. So, I installed a see-through filter between the pump and tank and another between the pump and carb. BTW, the Cuda has a 340 with a carb. No EFI.

It is my understanding that EFI is less forgiving than a carb regarding micro impurities in the fuel.

 

[RJRENTON]

IMO, putting the fuel filter b4 the pump will increase the pump's negative suction pressure, which USUALLY results in lower pump volume. The pump is trying to pull thru a 3/8" supply line, originating at the tank, going thru several bends and elevation changes and any additional restrictions (inline filter) will likely result in possible fuel starvation at high demand levels (racing or other 1/4 mile contests). Mopar placed the filter after the pump and b4 the carb(s) to minimize any chance of restriction. Just my opinion of course.
BOB RENTON

 

[biomedtechguy]

IMO, putting the fuel filter b4 the pump will increase the pump's negative suction pressure, which USUALLY results in lower pump volume. The pump is trying to pull thru a 3/8" supply line, originating at the tank, going thru several bends and elevation changes and any additional restrictions (inline filter) will likely result in possible fuel starvation at high demand levels (racing or other 1/4 mile contests). Mopar placed the filter after the pump and b4 the carb(s) to minimize any chance of restriction. Just my opinion of course.
BOB RENTON

Thanks Bob.
I know that I have seen "filter before pump" as a no-no more than once.
For some strange reason, that is how it was and has been since I got the car 6 odd years ago. At least they used a WIX filter...
My fuel line is 3/8, as you said, because it's a 6bbl V-code.

 

[themechanic]

IIRC, doesn't Holley EFI kit come with a pre-filter between the tank and external pump in their kit?

Anyway, just do as Edelbrock, Holley, or whoever made your EFI system says per their instructions and you will be fine. Plus, you will comply with any warranty issues.

 

[biomedtechguy]

No EFI.
Promax modded Holley 3x2bbl carbs.
I replaced the WIX fuel filter with a new identical WIX filter, that is in the length of rubber hose that goes from the engine end of the hard line that comes from the gas tank and the fuel pump. Then I also have a 40 micron metal mesh fuel filter that was an integrated module of the lower fuel line from Promax.
I still have to look at my 70 Service Manual too.
Time/Money...one man small business.
Always more of one than the other, and my time spent not working directly costs me lost income.
That's one reason why I ask a lot of questions here.
Thanks.

 

[themechanic]

All my previous posts were with the understanding you were building a high HP engine with EFI. Sorry.

 

[biomedtechguy]

All my previous posts were with the understanding you were building a high HP engine with EFI. Sorry.

No need for apologies.
Just working on the basics.
My current warmed over 440 6bbl should have the best opportunity to make the most of its potential, and by covering some of the basics now that will carry over moving forward, that's one less variable or detriment to stand in the way of getting the most out of future upgrades and investments.

 

[themechanic]

If it helps, I will be removing the pre-filter from the Cuda after the new tank and fuel lines are installed.