Looking for some advice on my EFI/Carb fuel system swap

[tokarz1]

I want to thank you all again for the help. I was able to find a website that has an approximate peak gph fuel required fuel flow formula.

https://blog.cantonracingproducts.com/blog/how_to_estimate_your_engines_fuel_flow

So in calculating my 430hp FWHP engine I come up with this

430 hp x .50 = 215 lbs/hr
then...
215 lbs/hr / 6.25 lbs/gal = 34.4 gph or 130.5 lph

I also downloaded their suggested line size.

 

[tokarz1]

So, I believe I am after an in-tank fuel pump that is compatible with the Grand National sending unit and flows at least 35 gph/130 lph. Would using a larger pump be a detriment on anything? I was thinking of using one of the Walbro pumps (190 lph or 255 lph) I had mentioned in one of my earlier reply's. I will be using a regulator to lower the pressure to 6.5 psi to the carburetor with a return line.

 

[64nailhead]

There is nothing wrong with using a Walbro 255. And the link you attached indicates that your 3/8" line is more than adequate for what you're trying to accomplish.

Supercharged111 If the regulator you linked includes a spring to work as you described, then that regulator is within it's design limit - sounds like the perfect FPR for multiple applications.

 

[64nailhead]

78Delta88 Supercharged111

I'm sure most of us understand the correlation between pressure and volume. An electric motor is meant to run within a certain range/duty cycle. Running it well above or below the intended range will lead to a shorter lifespan.

This is a very good discussion for the pages of this thread. More than one way to skin a cat.

 

[78Delta88]

64Nailhead; concur.

The regulator I posted ... Holley 12-803BP is actually designed for the TPI/TBI to Carb conversion.

And as you mentioned, a high inlet pressure it can not do. It maybe will for awhile but then fail.

When I was looking into this a year ago as I had same questions, higher pressure rated pumps can't be stepped down that much, and I did not find one that could. Maybe it's out there, but I did not locate any that were affordable. The best I could find was two in series to step it down.

The one I mentioned has a price from Jegs at ...100-ish. I special ordered from AutoZone got it for much less.

 

[78Delta88]

So, I believe I am after an in-tank fuel pump that is compatible with the Grand National sending unit and flows at least 35 gph/130 lph. Would using a larger pump be a detriment on anything? I was thinking of using one of the Walbro pumps (190 lph or 255 lph) I had mentioned in one of my earlier reply's. I will be using a regulator to lower the pressure to 6.5 psi to the carburetor with a return line.

With the charting you mention you can see 3/8 line is smallest you want to go for supply and should work with nitrous later on if you go there. 5/16 ok for 283, 302, 318, 305 mild builds but as you get 350 and bigger 3/8 is the way to go.

190 lph is about 50 gph, so ok for nitrous with a splitter. But as just a single source to the carb I would think would be too much. You might find its not enough when you add the nitrous (if and or when), but for now maybe too much over kill.

Pics attached are the units going back in the caprice. Originally a 305 TBI. Going to go to 327 Small Journal, 750cfm Holley and Progressive Ignition Distributor set at Max 7000, and from everything I researched is what I came up with.

TBI electric pump 12-803BP regulator and I'm building my own inlet system with cooler and fan, external large capacity filter (Arizona Dusty Dirty....) Regulated inlet with gauge. Also add ice can if needed, but I really don't plan to race probably just get a couple strips. Then 4L80E manual shift and haven't decided on rear gears yet.

The math I used lbs at 6 and not 6.25, so changes things a little but not much and it's a problem with using averages and one calculation over another.

If you find a pump close to your 35 GPH go for it. Yet you can still get the same with more readily available 30 GPH units, and from Factory they only setup the 454 for 30 GPH from the 70's.

Another thing I'm going to check is the GM 8.1 EFI. See where that's rated.

Edit... Rereading your question.

Sure. GN pump at 35gph, 3/8 supply, Holley 12-803 set at 6.5. Return I would suggest 3/8, but if 5/16 is already there use it and see. If ever going nitrous... Yeah definitely 3/8 return.

When I did the sniper system on the 57 I made hardline return 3/8. Pain in the ...., yet it's closed loop and I didn't want any restriction so just 3/8 supply and 3/8 return... Easy easy.

As you are doing your build and your frame off I would be more inclined to do both 3/8 hard line, but just my opinion.

 

[tokarz1]

When I talked with Aeromotive they recommended their "EFI to Carb dual stage fuel pressure regulator" P/N 13220. You adjust the main pressure coming from the pump to double what you want to run to the carburetor, and then adjust that down to the desired pressure you want for the carburetor.

https://aeromotiveinc.com/product/efi-2-carb-dual-fuel-pressure-regulator/

It is a pricey piece and after some looking around it appears to be a bypass regulator and a deadhead regulator as one unit.

https://aeromotiveinc.com/product/universal-bypass-regulator/
https://aeromotiveinc.com/product/carbureted-adjustable-regulator-billet-2-port-an-6/

 

[78Delta88]

Be careful of those many are not the quality you assume. Doing my research last year, lots of comments, lots of problems.

The one at the top is similar to what I mentioned. The input steps down to level that the next one can handle and then steps down to Carb pressure. Many fail, many had issues with needing to change regulator springs and many had the threads improperly machined.

The next one shown is turbo referenced but most I looked at were 30 psi or higher and could not reduce to Carb. They are designed for 4 CYL EFI w/turbo.

I'm not saying Aeromotive is bad, I'm not. Yet many copies coming out of Asia that are not as good as they should be, and many are cheap copy ...clones.

 

[tokarz1]

Be careful of those many are not the quality you assume. Doing my research last year, lots of comments, lots of problems.

The one at the top is similar to what I mentioned. The input steps down to level that the next one can handle and then steps down to Carb pressure. Many fail, many had issues with needing to change regulator springs and many had the threads improperly machined.

The next one shown is turbo referenced but most I looked at were 30 psi or higher and could not reduce to Carb. They are designed for 4 CYL EFI w/turbo.

I'm not saying Aeromotive is bad, I'm not. Yet many copies coming out of Asia that are not as good as they should be, and many are cheap copy ...clones.

Thanks again for your advice. In doing a search for the recommended one from Aeromotive I found so many low-priced knockoffs out there.

 

[78Delta88]

Thanks again for your advice. In doing a search for the recommended one from Aeromotive I found so many low-priced knockoffs out there.

Yes.. I think Aeromotive are ok, but I see that unit ... Size and shape and cringe.

I did look into the 8.1 Chevy. And stock replacement pump is 145 LPH which ends up being 38.3 GPH. I looked under rock auto, 2007 Chevy 3500, Air Fuel, fuel pump.