TBI swap ???

[sdkid]

Got a buddy that is swapping a tbi setup from a van into his 84 or so k20. What is the most economical route for the fuel pump and tank. Are the pumps intank or frame mount? Can he get newer saddle tanks that will accept intank pumps?

[DirtyLarry]

I actually have not had good luck with the frame mounted pump on my ’78 with the 8.1L. This truck is an off-road truck that cruises along on mountain trails at 3 MPH for hours on end with little wind blowing over the pump to help keep it cool. I even mounted the pump in a nice spot on the frame behind a cross member to shield it from the exhaust heat. The truck hasn’t died on me yet, it just doesn’t like to restart after a brief stop on the trails after creeping along slowly for a while as the fuel just cavitates inside the pump until it cools off. Maybe for a street truck the frame mounted pump will work fine.

I am now in the middle of swapping on a 1987 fuel tank and sending unit with a high pressure AC Delco EP241 fuel pump to feed the 8.1L. Rather than spending the money on two 1987 tanks, sending units, corvette fuel pumps, etc….I chose to run one in-tank pump on the RH side and a low pressure/high volume pump on the center cross member in between the two fuel tanks to act as a transfer pump to fill the RH tank from the LH tank. I am still waiting on the sending unit to come in from Summit before bolting it all together to see how well this will work in the real world.

The 1987 EFI 16 gallon fuel tank through LMC is pn 32-5937
The 1987 EFI sending unit through Summit is a RNB-692-027

The current frame mounted pump set up.

[joe231]

wow that 8.1 has got to be a MONSTER in there, huh?
so the new-gen Chevy engines have the same bell housing pattern?

[rfmaster]

If you have a pair of older, non EFI dual tanks there is couple of ways to get EFI - TBI working. One is to use one tank as transfer tank - DirtyLarry.

The other way is a bit more complicated, but it works very well. For my conversion built a dual loop fuel overflow system. Overflow system uses a small, four port surge tank (1.5 qts) which is being feed by a low pressure (< 6psi) frame rail mounted fuel pump with a fuel selector switch that allows me to select port or starboard side tanks. Excess fuel is returned back via another selector valve back to the gas tank from which it was drawn. Surge tank is always full and it provides uninterrupted fuel source for high pressure EFI pump which brings fuel to TB. TB return fuel line dumps back into surge tank and excess fuel get returned back to sourced gas tank. System uses two frame mounted fuel pumps (one low pressure fuel pickup, the other high pressure for TB) couple of fuel selector valves, lots of 3/8" hoses and tubing and somewhat resembles B-737! I guess I got carried away, but it works for me!! A year an half after completing conversion I have not had a single hiccup. BTW I use Carter fuel pumps.

//RF

[DirtyLarry]

Yes, the 8.1L honks very well. That is the glory of GM, they have used the same bell housing pattern on the Chevrolet V8 engines for over 50 years!

Here are two videos from when the first day it got running and before the fine tuning to the controller were done. The sound quality of my little camera sucks but you can hear that frame mounted pump screaming like crazy.

rfmaster,

Dude, that does sound complicated.

http://www.youtube.com/watch?v=avyjEr4bnGA

http://www.youtube.com/watch?v=SAYW1OXyEIU

[rfmaster]

Hey Larry

Yes, it is a bit more complicated for a truck - now that I look back, but we used a conceptually similar system on a fishing boat (actually we had four main storage tanks, day tank, a pair of surge tanks and whole slew of transfer valves, filters and pumps) feeding a pair DD and auxiliary generator. It kinda brings old memories from younger days. Besides, it was fun putting it all together! With exception of a surge tank (custom weld job) all other components are readily available.

Surge tank

[DirtyLarry]

rfmaster,

You’re a heck of a lot smarter than I am to figure that one out. I still don’t think I got it figured out even after reading your post a dozen times. Almost looks like aircraft or UFO type technology.

I think I better stick with one in-tank pump with a transfer pump to move fuel from the LH tank to the RH.

Good info though!

[rfmaster]

Larry

OK, pictures (and diagrams - I am an engineer) are worth a thousands words... Take a look at my system design notes - it should make sense - High pressure Fuel pump is a Carter P5001, Low pressure is Carter 74017, 'F' stands for filters, UN50 are fuel valves, etc.

and obligatory youtube video

YouTube - Carb to TBI conversion

That's a very nice setup you have - 8.1L engine is the best drive train ever designed and put together by GM!!! GL!

System diagram

[DirtyLarry]

That is an impressive layout drawing for a hobby project. Better than many of the engineering documents the engineers in my group draft for new production vehicles!

You certainly did a great job engineering that system!