I just finished installing a Holley pro-jection TBI unit on a 305, I used a '93 pickup 350 intake manifold to make bolting up things easier, the TBI fitted nicelly there, just had to enlarge the bores a bit since the holley barrels are bigger than the chevy's.

I'm experiencing a ecm calibration problem, when the motor revs up under heavy load it stumbles a couple of times, like hicups then keeps revving fine and pulls very well

I have tried going lean then rich in the main fuel **** but seems like it won't go away, any suggestions? anybody has used a similar setup?

I'm not using a O2 sensor, so I can't tell if it's lean or rich when the problem happens.

thanks

Augusto.

 

Is that a Holley ECU? Does it run open loop with no NB02 sensor? I saw an early Edelbrock TBI with its ECU on a 350 in my buddies shop. I believe that too was open loop only. It was retrofitted on a 1977 Olds Cutlass. Something tells me the fuel mapping did not have a VE table and was pretty archaic. There was a controler of sorts laying on passanger seat. Spark was a standard mechanic distributor.

 

yes it is a holley ECU,
I solved the problem today, it was my fault, I was too lazy to install the ECM power lead using a relay to get juice directly from the battery, so I installed a wire from the HEI hot terminal to the ECM, I beleive this gave a dirty (pulsating or something) to the ECM making it behave weird, so I followed the instructions and wired it using a relay, now the power goes directly from the battery to the ECM, all problems gone, even I had to lean all the parameters, maybe I wasn't geting full voltage to the ECM, now the motor runs great, never did so well with a carburator and I tried several, from the ugly 2 barrels ( both the old 2MC to the.. I forgot the name of that Q-jet sawed in half) to a well tuned and modified Q-jet, this TBI really works nice and calibrating it was a breeze, I think it would work better in a 350 since it feels a bit overcarburated, it flows 625 CFM wich is too much for a stock 305, but runs great anyway.

Augusto.