[rfmaster]

Pancake welcome to the 67-72 board.

Your questions regarding TBI conversion are in the spirit of this thread and we are glad to help you with your project.

First things first - in your post you stated that you put a 'mild RV cam' into your rebuilt 350. Do you have specs for this cam???? This is very important as cam selection may make or break TBI conversion!!! I am not trying to scare you. Most RV cams are very tame, but there are couple parameters - LSA that make EFI tuning easy or difficult.

For a low cost TBI system I would look for (JY or running beater) 350 CID equipped 87-92 Burban or truck. These come equipped with 1227747 ECM's - grab everything that is connected to ECM harness:
CTS
EGRV + EGR
MAP
ESC
KS
Optional (Dizzy + coil) or find early full size dizzy from CCC equipped SBC car or truck. This is a subject for a long discussion and should be looked into separately.
TB (TPS + IAC + Injectors)
VSS and DRAC if available
CCP canister (optional)
Air diverter valve (optional)
relays, brackets, etc
O2 should be sourced new!


ECM (in trucks) is located just behind glove box and can (should) be removed intact. Please note that you can still use 305 equipped TBI system, but you'll have to do couple of upgrades down the road (EPROM, KS, Injectors). 1227747 ECM is very common, dirt cheap, has been hacked backwards and forwards, and can be easily updated (re-programmed)

For a little bit more work a car based TBI is an excellent foundation for a CARB to EFI conversion. Look for F-bodies 88-92 with (LO3) 305 TBI, B-Body both were equipped with LO3 (305) and LO5 (350) TBI systems. Early passenger cars TBI systems were based on 1228746 ECM. Car's emission requirements were (are) more stringent and more control and sensor lines were made available in '8746 ECM. These included ITS, CCP control, AC enabled and PS switch. In the 90's B-Bodies received an upgraded version of '8746 ECM - 16196395

From ease of conversion #1 1227747 from 350 CID truck (look for ASDU, ASDZ broadcast codes), #2 1228746, but this will require EPROM work, #3 16196395 from B-body, also will require some EPROM work or EBL conversion (#1, 2, or 3) for ultimate flexibility and ease of tuning.

I have sourced all my harnesses from JY donors - I can not comment on aftermarket harnesses. Either Painless or Howell should work just fine. If you have to pass smog - than you must have functioning AIR diverter you'll need harness that has connector that controls diverter.

Now for the TBI conversion questions:
Q1) The neutral safety switch is re-wired so I can start the truck in gear if I need to. Do I just ground the N/S switch? Is it wire B-10? What do I do with the wire if I decide to go to the TH400?
A1) With manual there are couple of options. For now just leave it open.


Q2) After reading about the VSS I will be putting one on the conversion. The VSS connects top the tranny or t-case? Where can I get a cheap one? If I put a TH400 in will I need to change the VSS? The TH400 will have a manual valve body.
A2) Get VSS from JTR - it is in line with your speedometer cable into trany.


Q3) Where do I put the knock sensor?
A3) Passenger side water jacket drain plug - just above oil pan rail. Be forewarned that it is best to remove this plug while engine is out of the engine bay. These plugs are known to rust-in and break while removing. Drilling a pilot hole and right size easy-out is only way I know to get them out! It is PITA.


Q4) Where I put the coolant temp sensor?
A4) CTS should be placed within 2- 3 inches of thermostat housing in intake manifold. Most after market manifolds have multiple suitable tapped holes.


Q5) I do not have A/C but would like to use the wire from the ECM to boost idle when I need to use the winch. Any suggestions how I would do this? Put in a toggle switch?
A5) This is a very easy circuit to implement. - Run a wire from winch relay coil to ECM AC requested input (ECM Pin-B8) line.


Q6) Which ECM should I look for? Serial #? and will I have to get it re-programed....new PROM?
A6) See discussion above, but if you get lucky...


Q7) I have a plastic fuel cell in the rig now. I might go to a stock fuel tank with the pump in it in the future. What external pump should I get to ust the fuel cell? Do you have a part number? Do I need a fuel regulator or is this built into the TBI? I do need a return line right?
A7) For TBI conversion you'll have to have fuel delivery system that works. You'll need three lines going to your gas tank. 3/8 fuel supply, 5/16” (or 3/8") and another 5/16" for vapor line - CCP. Tank must have internal baffles to keep fuel sock from uncovering. For external mounting I used Carter P74017. You do not need fuel pressure regulator - TB has a simple spring based FP regulator. Do not go crazy with high fuel pressure pumps!


Q7) I have also read about a charcoal canister? Do i need one?
A7) Yes, it keeps fuel vapors from escaping into atmosphere. With CCP fumes are delivered into TB and consumed instead of being lost.