1991 V3500 Project Heavy Hauler

[hardcore4life]

So you're planning an 8.1 swap I take it?

[MTCK]

Originally Posted by hardcore4life

So you're planning an 8.1 swap I take it?

Yup, that's the plan. Not looking great for this winter as I haven't found any shop space and this truck is about 10' too long to fit in my garage.

[DirtyLarry]

Very cool Marcus! Somehow I missed this thread of yours. Looks like a very clean rig to play with. Love the Suburban interior and the swapped in tilt column in there too.….same color of Suburban seats I have in the K10. That rubber floor mat is a killer to work with huh? That is the same mat in my K10 and it is tough as nails to work with. You almost need a blow torch and chainsaw to cut and mold it. Looks like it turned out great. You will like that mat as it is practically impossible to hurt it.

Let me know when you want to start talking 8.1L stuff. You know I have the recipe at hand and it is fresh in my mind again as I am doing one in the Polar Bear Suburban this winter. Right now I’m still working on the engine internals and gathering install bits. This one is getting a Raylar cam just to see how much more a cam really wakes up an 8.1. Hope to install the engine around Decemberish.

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[MTCK]

Thanks Larry, yeah that mat is a PITA, but bulletproof. I'm still not 100% happy with how it is laying near the firewall, but the rest of it has settled down. That's exciting about the Raylar cam. They have some pretty cool vids of some wild 8.1's on their web site.

I've actually been referencing your good write up on CK5 quite a bit as I plan. Do you have a good source for purchasing new workhorse parts with "reasonable" shipping? I'm going to try using the in-tank sending units for the fuel system and the AC Delco EP241 pumps along with a direct replacement switch rated at 65 psi. Check out the data sheet link below. I think the previous version of this part from Pollak was not rated for as much pressure.

http://products.pollakaftermarket.co...S_41-revdd.pdf

It is supposed to plug right in where the stock 87-91 valve goes using the stock switch. The three tank setup is intriguing, though I would need a loan to put 80 gallons in at a time if I added a suburban tank in the rear. $135 was bad enough last week...

[DirtyLarry]

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.

[MTCK]

Thanks for the info Larry. Good call on the different pumps - I would have ordered the wrong ones. I'm having a hard time figuring out why the valve you had was causing that much pressure. I wonder if you got a bad unit? Fuel return volume should only be a function of the fuel pump, pressure at the regulator, head loss through the lines and fuel used by the engine. The higher the pressure at your regulator, the lower the flow as the pump has to work harder. I suppose if you have a large diameter return line all the way to the valve then necked down that could cause some increase in pressure. 10mm ID is about 1.5 the cross sectional area of a 5/16" ID.

I'll do some more research and maybe even a little trial and error. I am interested in the wiring for a three tank system that was shown on that schematic. 80 gallons would definitely get me to the next station, and it would be nice to not mess with transfer pumps. I always forgot to turn mine off on my '77, as I had a system very similar to yours. $4/ gallon fuel all over the road!

Winter is here. I was waiting for a dump trailer to come available but it never did, so I hauled off most of the spoils from my grubbing project with the pickup. It was easy to load and a son of a gun to shovel out. I guessed the mix of roots and organics and dirt was much lighter than it really was. Still had about 3" of up travel to the bump stops with this load, but went over GVW by quite a bit. Whoops. Rides like a Cadillac with 3 tons in the back. Surprisingly the weight over the front axle was only about 500 lbs. more than when the truck was empty. That means I had almost 9k over the rear axle. The tires were cool but I won't do that again, even if it was just a couple miles across town.

I took the mini ex back this morning and the boost feature on the brake controller worked great. It was much more solid feeling while braking, even though the roads were slick. $$ well spent in my opinion.

[y5mgisi]

Good to see it get so much use!