Will the 307 be enough?

[TClassic]

Originally posted by Tow Man


Is the $10.00 difference that big of a deal? I spend more than that on coffee a day

It has NOTHING to do with the PRICE of the Pump, its folks like myself that received a 307 in the mail instead of a 340, and rembering the Precision testing, saying it was Basically a PERFECT pump up to LOW 11's, installed it!!

So NOW, I've got to Drop the Tank, Shell out ANOTHER ~120 or so bucks and do the DAM THING all over again!!!

 

[87GN_70GS]

Date: Mon, 28 Feb 2000 08:14:27 -0600

While preparing to put in my newly acquired Walbro 307 fuel pump, I decided to "tweak" it. I shimmed the pressure relief valve and then measured flow capacity at various pressures and supply voltages. Before the conversion, I measured flowrates and got very close to (slightly better than) published 307 flowrates.
After the conversion, it outflowed a stock 340 above 60 psi.
The conversion is pretty simple. The relief spring is visible in the black plastic top near the outlet. It is in an approx. 0.110" wide oval opening. A #10 ga copper wire (0.102") will fit in there nicely. Just use a small screwdriver to pull down the top of the spring and insert a right angle piece of copper wire
(~3/8" by ~1/4"). Make the angle slightIy more than 90 deg. I tiewrapped it to hold it in place. After the conversion, this pump outflowed published numbers (above 60 psi) for both Red's XP-plus and Ron Gregory's 340 website numbers. For example. @12v I got: 54 gph @ 60 psi, 50 gph @ 70 psi, 47 @ 80, 42 @ 90, 37 @ 100. At 13.5v: 65 gph@ 60 psi, 61.5 @ 70.
Notes: The relief spring looks to be almost solid (no gaps between coils), the 10 ga wire might be too much. Relief pressures were way over 100 psi. The data collected was from a sample of one, YMMV. I wonder what a shimmed 340 will do?
HTH.

Scott Moody
moodysj@redstone.army.mil