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Old 09-30-2014, 04:40 PM   #105
DirtyLarry
Windy Corner of a Dirty Street
 
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Join Date: Jun 2003
Location: Pueblo West, Colorado
Posts: 2,926
Re: 1991 V3500 Project Heavy Hauler

Yeah, I hear you. I am not real happy with the way mine lays near the trans tunnel but it is as good as it will get being it is so stiff and thick.

Hehe, I know I am excited to try a RayLar cam! Should be interesting.

I might have a source for Workhorse parts. Let me know what specifically you would need. In all reality, if you’re not running A/C there really isn’t anything that Workhorse has that you can’t find through GM, Ebay or salvage yards. The highly sought after high mount A/C brackets through Workhorse are now extinct. All gone… the only ones to be found now would be from G-van engines at salvage yards or from PSI who now builds the 8.1L and 8.8L.

The pressure rating of the Pollak switch valve is not the issue. The issue comes in where the return port in the switch valve is too small (5/16) and the 8.1L’s with the return type fuel rail use a large return line much larger than 5/16. I think the return line on the 8.1L is around 10mm but in any event, the return ports on the switch valve are too small and restrict the fuel return which drives up head pressure. I tried to use the Pollak valve but the little ports caused the head pressure to run at 100 psi. Once I disconnected the return line from the switch valve the fuel pressure went down to normal. In the end, I gave up on the idea of using a switch valve. Instead I have an EP241 on a 1987 TBI sending unit in the right side tank which is just a storage tank. That pump transfers fuel to the LH tank byway of a switch on the dash.

Now, if you used a later model 8.1L with the returnless fuel rail you might be able to figure out a work around with that switch valve. I’ve never really researched the returnless fuel rails as I prefer the return type because they have an adjustable fuel regular built into the rail. The 8.1L I’m doing for the Suburban had the later type returnless fuel rail but I took it off and purchased a new return type fuel rail for it because I like having the adjustable regulator. 8.1L’s love higher than stock fuel pressure. They really respond well to 67-68 psi fuel pressure.

BTW…. The fuel pumps you would need to run an 8.1L are actually the EP381. The EP381 will fit on your existing sending units no different than the pumps that are on them now. You probably read where I had an EP241 but that was back when I was running the truck on a marine MEFI-4 ECM which runs on lower fuel pressure (~40 psi) like the old school TPI engine. I ran the EP241 for a short while after converting it to the MAF OBDII harness on a truck P59 ECM which requires around 62 psi but found the EP241 did not maintain fuel pressure at wide open throttle so I swapped in an EP381. Problem sovled. Confused even more now? BTW....the old EP241 pump that used to supply the engine actually lives in the RH tank now and is used just as a transfer pump.
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