Hi All,
After reading this thread, I decided to take the plunge.
Purpose: To remove any possible restriction from the return fuel line(s) before upgrading to a better fuel pump (Aeromotive 340).
Tools needed: New o-ring (selection), drill bit selection, small metal lathe.
Phase 1: Modified my Accufab regulator (as per above thread) with a few changes. I was thinking erosion might become a problem as fuel rips across the bare aluminum left by drilling the return orifice, so I found and installed a bushing like the original only larger. Didn't see any benefit in changing the inlet diameter (it's already ~ 0.250") especially if it were to intrude into the outlet port. The smallest diameter in the regulator is now the outlet port at 0.234" ID (drilled with a letter "A" bit) as opposed to the 0.187" original. That's a 56% increase in area.
Phase 2: Got the Jeg's 06 x 14mm-1.5 adapter out and had a look, man is that center ID small! Again, 0.187" ID is prolly going to be a bottleneck for a good fuel pump. A letter "L" drill (0.290") fits snugly into the 06 end of the fitting, that's a pretty nice increase. The o-ring seat ID in the regulator is 0.296" and if we can bore the fitting, it will no longer be the restriction. However, doing this will move the "seal" of the o-ring from the ID of the bore to the "face". I didn't see this as being a problem and the Accufab's stock o-ring seat (ID) remains untouched so the regulator can be used with either fitting. Screwing the fitting into the regulator (minus the o-ring) bottoms out on the face and leaves an 0.080" gap between the base of the regulator and the nut of the fitting. Step 1 is to bore the fitting with the "L" bit, which also removes the inner lip that holds the o-ring. Step 2 is to chuck the fitting in a lathe (yeah, it's nice to have one!) and turn the "o-ring end" of the fitting to approximately 0.330" OD so as to leave a wall that is 0.020" thick and about 0.100" deep. Step 3, since the walls are only 0.020", it's easy to "bell" the mouth with a round hand tool, like a screwdriver shaft. This will help hold the o-ring in place. Step 4, the depth of the cut is deeper than the o-ring I'm using, so now we turn the end off so the overall depth is about 0.020 less than the thickness of the o-ring. This allows for some o-ring compression and also moves the adapter further up into the regulator body so now there's 0.020" clearance between the body and nut, a small gain none-the-less. Now the fitting is completely out of the picture restriction-wise, as the ID has been increased from 0.187" to 0.288" (which is a 236% increase in area). I did look at the Jeg's 06 x 16mm-1.5 inlet fitting but didn't see any gains to be had, as the ID of the o-ring boss is about the same as the (0.288) diameter of the 06 flare end.
Phase 3: To be continued, waiting on parts! This will be upgrading the factory "engine manifold assembly" return line from 5/16" to 3/8". After seeing a friends truck burn to the ground recently, I'm looking carefully at all my hoses and these original 25 yo hoses are in sad shape. I can't see paying close to $200 and getting the same old 5/16" return line. I bought (and will bend to the exact same shape) a piece of 3/8" steel brake line to replace the factory 5/16" line. To get from the 06 fittings to the steel lines there are several options. Discount Hydraulic Hose has dedicated tube to flare conversion fittings (for $28 apiece!) or you can buy 2 "Convert-A-Flare" pieces (#418 tube nut and #419 tube sleeve) plus the flare fitting of your choice for around $3.80 per "unit". I bought 6 each "sets" of the Convert-A Flares plus 06 flare unions, and an 06x90° swivel. 2 will go on my chassis lines (which are both 3/8" already), 2 will go on the engine manifold lines by the crank sensor, and 2 will go on the supply and return rail/regulator ends. The swivel goes under the regulator. Between the rail fittings and the chassis fittings will be a pair of 06 hoses (each with Jeg's brand black fittings), 90° at the engine and 45° at the chassis. The total for all this was $144 in parts, not including the piece of Jeg's black cloth-braided 06 hose I had left over from another project.
I don't know for sure if the Aeromotive pump would have overwhelmed my return line, but I KNOW it won't now. Plus I have a fuel line with all new rubber lines and it's got universally replaceable parts...
After reading this thread, I decided to take the plunge.
Purpose: To remove any possible restriction from the return fuel line(s) before upgrading to a better fuel pump (Aeromotive 340).
Tools needed: New o-ring (selection), drill bit selection, small metal lathe.
Phase 1: Modified my Accufab regulator (as per above thread) with a few changes. I was thinking erosion might become a problem as fuel rips across the bare aluminum left by drilling the return orifice, so I found and installed a bushing like the original only larger. Didn't see any benefit in changing the inlet diameter (it's already ~ 0.250") especially if it were to intrude into the outlet port. The smallest diameter in the regulator is now the outlet port at 0.234" ID (drilled with a letter "A" bit) as opposed to the 0.187" original. That's a 56% increase in area.
Phase 2: Got the Jeg's 06 x 14mm-1.5 adapter out and had a look, man is that center ID small! Again, 0.187" ID is prolly going to be a bottleneck for a good fuel pump. A letter "L" drill (0.290") fits snugly into the 06 end of the fitting, that's a pretty nice increase. The o-ring seat ID in the regulator is 0.296" and if we can bore the fitting, it will no longer be the restriction. However, doing this will move the "seal" of the o-ring from the ID of the bore to the "face". I didn't see this as being a problem and the Accufab's stock o-ring seat (ID) remains untouched so the regulator can be used with either fitting. Screwing the fitting into the regulator (minus the o-ring) bottoms out on the face and leaves an 0.080" gap between the base of the regulator and the nut of the fitting. Step 1 is to bore the fitting with the "L" bit, which also removes the inner lip that holds the o-ring. Step 2 is to chuck the fitting in a lathe (yeah, it's nice to have one!) and turn the "o-ring end" of the fitting to approximately 0.330" OD so as to leave a wall that is 0.020" thick and about 0.100" deep. Step 3, since the walls are only 0.020", it's easy to "bell" the mouth with a round hand tool, like a screwdriver shaft. This will help hold the o-ring in place. Step 4, the depth of the cut is deeper than the o-ring I'm using, so now we turn the end off so the overall depth is about 0.020 less than the thickness of the o-ring. This allows for some o-ring compression and also moves the adapter further up into the regulator body so now there's 0.020" clearance between the body and nut, a small gain none-the-less. Now the fitting is completely out of the picture restriction-wise, as the ID has been increased from 0.187" to 0.288" (which is a 236% increase in area). I did look at the Jeg's 06 x 16mm-1.5 inlet fitting but didn't see any gains to be had, as the ID of the o-ring boss is about the same as the (0.288) diameter of the 06 flare end.
Phase 3: To be continued, waiting on parts! This will be upgrading the factory "engine manifold assembly" return line from 5/16" to 3/8". After seeing a friends truck burn to the ground recently, I'm looking carefully at all my hoses and these original 25 yo hoses are in sad shape. I can't see paying close to $200 and getting the same old 5/16" return line. I bought (and will bend to the exact same shape) a piece of 3/8" steel brake line to replace the factory 5/16" line. To get from the 06 fittings to the steel lines there are several options. Discount Hydraulic Hose has dedicated tube to flare conversion fittings (for $28 apiece!) or you can buy 2 "Convert-A-Flare" pieces (#418 tube nut and #419 tube sleeve) plus the flare fitting of your choice for around $3.80 per "unit". I bought 6 each "sets" of the Convert-A Flares plus 06 flare unions, and an 06x90° swivel. 2 will go on my chassis lines (which are both 3/8" already), 2 will go on the engine manifold lines by the crank sensor, and 2 will go on the supply and return rail/regulator ends. The swivel goes under the regulator. Between the rail fittings and the chassis fittings will be a pair of 06 hoses (each with Jeg's brand black fittings), 90° at the engine and 45° at the chassis. The total for all this was $144 in parts, not including the piece of Jeg's black cloth-braided 06 hose I had left over from another project.
I don't know for sure if the Aeromotive pump would have overwhelmed my return line, but I KNOW it won't now. Plus I have a fuel line with all new rubber lines and it's got universally replaceable parts...
