As guys seek and add more brute power to these Cummins, weak points surface, one being fuel flow to the Cummins and VP-44.
Some guys go to the expen$e of larger lines and fitting for the fuel
system, but for moderate power up around 400 HP or so, the stock lines
do a pretty decent job.
But for at least some degree of help - on a budget - consider this mod.
This is a simple drilling out of the fuel holes in the stock banjo
bolts that attache fuel lines to the fuel filter, Lift Pump, and VP-44.
The existing holes are in the neighborhood of about 1/8 inch - and can
be safely enlarged to about 3/16 for improved flow - here's a
before/after shot on a pair of banjo bolts:
As can be seen, quite a difference - and there are *4* of those holes
in each banjo bolt, so the flow improvement is significant. By the way,
these enlarged banjo bolts CAN be bought from several suppliers, but if
you have the tools, why not do your own?
Here's one of my bolts secured in a machinist's vise on my drill press:
I would strongly suggest use of a drill press for drilling these holes
- the placement and neatness is somewhat critical in order to maintain
proper sealing of the banjo fitting to it's mating surface. Here's what
the outer half of a banjo fitting looks like with the bolt out:
Hopefully, you can see the inner recess, where the fuel flows from the line and around into the holes drilled into the bolts.
And here is the setup with the bolt partly inserted:
This fitting is off the fuel line attachment to the VP-44, so the
included portion extending seen is where I attach the line going to my
fuel pressure gauge.
Here's the other fitting seen earlier, fully installed at the bottom of my fuel filter housing:
A few cautions:
1. Keep every fitting and hole drilled ABSOLUTELY as clean as possible, to keep damaging metallic garbage outta the VP-44!
2. Use something like a Dremel tool to clear and relieve the new holes.
both for smoothness, and also to avoid damaging the banjo shoulder
3. Either buy new shoulder washers, or be VERY careful of the old ones
- they are easy to lose during disassembly of the fittings.
4. Be every bit as conscious of clearing the INSIDE of the newly
drilled banjo as the outside. After drilling, chamfering and de-burring
mine, I used a suitable drill bit to ream out the inside of the bolt by
hand to remove internal burrs from the drilling process, I then flushed
inside and outside with strong shots of WD-40, and LOTS of compressed
That's about it - on mine, I also replaced the 1/4 inch hard line
between the fuel filter and the VP-44 with fuel rated neoprene line -
that is about the most restricted part of the line on our trucks, so it
was easy to do while I had stuff apart.