Do I really need the ecm.? I'm planning on an engine upgrade from the 305 tbi to a 350.

 

I think you can get rid of it if you switch to a carb. Otherwise I'm not sure.

 

If you're switching to Carb, you won't need the ECM..

Anything else, you will..

-LJ

 

Carb it is!

 

So switching from tbi to carb with a whole new motor: I won't need the ecm, right? What about the transmission? Can I stick with the stock 700r4? Everything should work though. Oh yeah, what about the fan? Sorry so many questions! Clueless about carb!

 

An ECM is only needed for electronic fuel injection. Carbs are standalone fuel management systems that require no electronic input. The only way you would need an ECM with a carb is going to a later style computer controlled Qjet - but I'd stay away from that swap if I were you.

Although the ECM does control both the cooling fan and torque converter lockup on the 700r4, you do not need it. You can buy an electric fan wiring kit at just about any parts store. As far as the lockup on the trans, all you need is a wiring kit for that too. Several companies make them. Summit Racing and Jegs are good sources. Also, just about any company that builds high performance 700r4's sell them too. Or, if you are inclined and have a good grasp on electrical work, you can make one yourself. They aren't that complex of a circuit.

 

If you have an electronic speedo (not sure what year your car is) then it's run through the ECM and won't work anymore. You can get an elcectronic aftermarket speedo and use that, or convert to mechanical speedo, all your other gauges will still work. You'll also need an HEI distributor because the one on your 305 is computer controlled. I got an Accel distributor off ebay 6 months ago for $60. And if you want to keep your stock fuel pump you'll need an adjustable regulator with a return port (carbs don't like more than 6psi) and you'll have to rewire the pump off the ignition because the computer tells it when to turn on and off too. Or you could take out the stock pump and go to a mechanical pump, or a low pressure electric pump.

It's been almost 5 years since I swapped from TBI to Edelbrock, so I don't remember the little details but it was well worth it for me. I picked up a lot of power with the 650 and HEI. Of course, I had to upgrade to a 750 when I built the 355, but that was worth it too.

 

Thanks!! BTW it's a 92. Any other needed info please post.

 

I figured I might as well reply even though you should be over at thirdgen.org asking this question.
As for the ecm, it does NOT control the fan on/off but it does control a few other things. The torque converter clutch was one and the other is your fuel pump prime. If you remove the ecm the fuel pump relay will not work and you'll be sitting there on a cold start waiting for the oil pressure to fill and kick on the fuel pump. That's if you keep the intake fuel pump. You could just hot wire it to be on with the ignition (easy enough). There is also the issue with the dissy. If you go with a mechanical dissy then there is no problem. I recommend doing that if you pull the ecm . Oh yeah, and the ecm also controls the shift light if it's a 5 speed.
All in all it's easy to scrap TBI. If you're not comfortable tuning TBI then by all means go carb, definatly more fun for the average hot rodder.