'87 TBI to Carb Help



I have an '87 3/4, 4x4, 350 TBI, TH400 chevy. I took the engine out of the truck and now I am putting in a carbureted 400sb. I took all the smog pump stuff off. I'm leaving the computer under the dash just because why bother to take it out. My problem is I'm going to run a mechanical fuel pump on the motor instead of my electric pumps in my dual tanks. My intentions are to disconnect the fuel pump relay in hopes that that will prevent the pumps from coming on. And this will allow the mechanical pump to draw the fuel through the electric pumps. If the fuel will not draw through the electric pumps then I will take the pumps out and just put a rubber hose in it's place. Anyone know if this will work? Or have a better idea. Also, I had two fuel lines going to the TBI unit. One line had an inline fuel filter along the frame. The other one didn't have a filter and seemed to come from my tank switching valve. Is it just a return line and I can block it off? I'm a little confused as to what I should do to make it one line going to my mechanical pump. I've also read that my shift points on the tranny may now be off with this new motor, how would I go about adjusting it. My next question is getting power to the distributor. My old setup had a stand alone coil with a small distributor. I had wires going to the coil then out of the coil to the distributor. There was also a plug that looks like it came right from the firewall to the distributor. Which would be the best wire to tap into to get my 12v to the new distributor. Any help on the mess I'm getting myself into would be greatly appreciated. This has been quite the learning experience. Thanks


Senior Member
Fairbanks AK
As far as sucking fuel through the pumps, can't help you there. An idea I would lean towards would be just getting a pressure regulator, and keeping the electric pumps. I know you can order these from summit racing, and other places I'm sure. I don't know about the return line hook up, but you should probably keep it, maybe hook it up to regulator if possible. As far as the distributer......... Does it have electronic spark control? This is, as I understand it, a set of sensors that detect knock and control advance. When I decomputerized a truck of mine, I just went to the parts store, got a high performance late 70's vacuum advance HEI unit. One wire to the ignition, vacuum advance, and works like a charm. Hope this helps.


PlowSite.com Addict
Have never tried it, but I don't think trying to draw fuel through the electric pumps is going to work. Keeping them as MTCK suggests would be the easiest way, IMO.

Unless you attach fittings and install a crossover line between the two tanks, you'll need to keep that dual tank switchover valve and use it. (With the stock tanks your truck has, I think it would be too much trouble to be worth it going to the crossover line idea)

For power, use a test light and see which wire off the firewall switches "on" and "off" with the ignition key. That will be the one you want to power your HEI distributor.


Junior Member
You can use the same sender assbly as you have in your truck gas tanks, but as you suggested, remove the pump and install a piece of hose, or just get a couple of senders(I have them here...I'm a wrecker, but you can probably get them local)from an 86 and down pickup and drop them in...the line without the filter is a return line, you can use your present setup of dual tank switching, etc, especially easy if you get a stock fuel pump with dual lines, then you can use your return line also...as for your distributer, use like suggested by the other fellow here, a late 70's one wire HEI with a vacum advance...as for shift points, they should be fine, as the turbo 400 uses electronic kickdown, utilizing a switch located either over your gas pedal, or possibly was on the throttle linkage of the throttle body on your old TBI...if not, again go to an 86+down truck equiped with a turbo 400 and grab the gas pedal bracket and switch and use that to control your shift points...the only thing I can't figure out is why your not keeping the fuel injection on your new motor...TBI is the only way to go, in my opinion....but to each his own...just my 2 cents....any other questions etc feel free to email me.......ED

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