Where is the best place to buy a Denso fuel pump?

[Steve Wood]

If you check the specs, the Denso pump does not put out much more volume at 70 psi than does the Walbro 340...

the problem is at idle when the volume is quite a bit more.  It can overwhelm the return line and make it impossible to control the fuel pressure at idle, or normal driving.

If you notice, Eric sells a 340 style pump and suggests a larger return line for just this problem.

In the end, if you are not going faster than high tens, there is nothing wrong with a Walbro.  It can be more reliable than one of the chinese imports.  In fact, as I recall, Dan was sneaking into the nines, but, he was pumping lotsa alky and supplementing the fuel that way.

(before you tell me how bad Walbros are, let us recall that it was the F numbered pump that had the problem a couple of years ago which Walbro recognized and fixed)

I guess I probably should replace the Walbro in my GN that I installed about 1990, tho.

[Steve Wood]

for those that are interested in a larger return line, here is Eric's recipe...a few posts down

http://www.turbotweak.com/forum/showthread.php?1968-return-fuel-line..

[TURBOPOWERED68]

Your 5/16 line is 44 years old correct?  Get rid of it....   

its only 6 years old

A 255lph pump would be a stock replacement. I would use a 3/8 return. For the above pumps that are over 275lph I would use AN-8 line which is close to 1/2inch

more work

[ULYCYC]

I like to use this as a guide. Did many this way without problems. This is minimun requirement. If you have bends or 90 deg fittings go to the next level.

Use these figures as a fuel line sizing standard:

• Up to 250 HP = 5/16" or -04 AN
• Up to 375 HP = 3/8" or -06 AN
• Up to 700 HP = 1/2" or -08 AN
• Up to 1000 HP = 5/8" or -10 AN
• Up to 1500 HP = 3/4" or -12 AN

Use these ratings to decide your return line sizing based upon fuel pump output:

• Up to 45 GPH = 5/16" or -04 AN
• Up to 90 GPH = 3/8" or -06 AN
• Up to 250 GPH = 1/2" or -08 AN
• Up to 450 GPH = 5/8" or -10 AN
• Up to 900 GPH = 3/4"or -12 AN

[Steve Wood]

Then the factory lines will not work?  3/8" delivery and 5/16" return.....obs ervation over 25 years says differently... but, if you are plumbing from scratch, then it will not hurt to go larger.

Experience seems to indicate the factory set up will work up to 550-600 hp which gets you into the high tens.   A bigger pump at the high pressure end will need larger lines...most I have seen went 1/2" on delivery and 3/8" on return...or a higher volume pump on the bottom end will work ok with 3/8" on both sides

Again, if looking for faster than high tens on gas alone, get a bigger pump that has more volume at 70 psi and replumb ...if running alky and not leaving the tens...stock line size will work with a pump similar to a 340

[TURBOPOWERED68]

i have a 340M in there now but its not working too well.
I guess i can go back to another 340M.

could this http://www.summitracing.com/parts/DAC-93036/ be used for the return line.
 

[ULYCYC]

No, Can't use more then 12 inches of  rubber line as per NHRA and also a good rule for the street. 

[ULYCYC]

The 340 will work fine with stock GN size feed and return lines as Steve said.   I found 10.80's the limit (no alchy).  When I worked with TommyX  he was having issues around 10.75 with alchy, 340 pump and stock lines.  All is at the end limits. I would step up and play it safe

[Steve Wood]

Also, it is not rated for Fuel Injection as per the note...

If you run a new line, it should be metal, or covered with brading so it cannot be cut by a flying rock, or such

[Steve Wood]

The 340 will work fine with stock GN size feed and return lines as Steve said.   I found 10.80's the limit (no alchy).  When I worked with TommyX  he was having issues around 10.75 with alchy, 340 pump and stock lines.  All is at the end limits. I would step up and play it safe

Exactly...over kill is always better than underkill.

You can go faster with twin alky, but, you are running a heckuva risk when there is a hiccup and the alky does not make up for the lack of gas.....From what I read, alky pumps need to be rebuilt ever couple of years to maintain performance...

BUT, I think it is very dangerous to try to faster than the upper tens using alky and twin lines are really upping the ante as well as a bitch to tune

Wanta go faster, buy race gas

[TURBOPOWERED68]

OK
i guess i'll have to rethink my fuel system as i am having pipe dreams of a 10.99 pass using Alky and N2O.

So in going back to the drawing board again
and having to run larger lines what would be the con of running two 1/2 inch lines?
Also would the sender's return tube have to be modified/enlarged/replaced?   

[TURBOPOWERED68]

Also, it is not rated for Fuel Injection as per the note...

If you run a new line, it should be metal, or covered with brading so it cannot be cut by a flying rock, or such

i figured return line=little to no pressure so the EFI rating wouldn't apply.
 

[TURBOPOWERED68]

The 340 will work fine with stock GN size feed and return lines as Steve said.   I found 10.80's the limit (no alchy).  When I worked with TommyX  he was having issues around 10.75 with alchy, 340 pump and stock lines.  All is at the end limits. I would step up and play it safe

Well like i said pipe dreams of 10.99s with ALKY.
 

[Steve Wood]

you should not need NOS to hit 10.99...just a single line alky kit and everything else working right if the turbo is the right size....NOS is one of those complications that can end up costing you a new engine.  Stop pipe dreaming and keep it real.  A 340 is plenty of fuel for such.  No need to try to deviate from what is known to work.

You don't need a larger return line if the fuel pressure adjusts to 43# at idle.

[ULYCYC]

I would not add NOS to the mix, many more $$$$ issues you would have to address.  Tuning alchy and NOS to come in at higher boost will be 

If your pump and lines were good I would say go for it. But you need a new pump. The price difference of a larger pump and lines are a lot cheaper then NOS, headgasket changes or a blown motor. Build for a 1/2 second faster for a safety margin.