I just got an '84 Firebird TA that has already had the 305 swapped for a Good Wrench 350, carburated 4 barrel. Does the PROM chip need to be changed when this swap is done? Although this was two owners and 40K miles ago, I do have all the paper work for the swap. There is no mention of a new/reprogramed PROM. Haven't found any existing links searching, should this be in the DIY Prom section? Hope you can help. Thanks

 

Seems like guys who have done your swap have never had an issue.

Most guys eliminate the computer quadrajet and ESC distributor for the older, 1970's versions and don't even run an ECM when this swap happens.

The truth is in the run; are YOU having problems while driving it around?

 

what he said, if they used a non computer controlled carb for the swap, then the computer now does nothing and swaping a prom would be pointless.

 

I would say "most guys" is an exaggeration.

The CC carb system is pretty simple, and pretty effective. It has spark tables based on RPMs and manifold vacuum, and the primary mixture is controlled via feedback from the O2 sensor. Neither of those is substantially affected by going from 305 to 350. You might improve things slightly with larger primary jets and reprogramming for the cold engine open-loop operation, but I never had any issues with my ZZ4 clone being operated by an '86 LG4 system.

The secondaries are completely mechanical open loop, and are tuned just like a non-CC q-jet.

The "computer doing nothing" becomes an issue with the torque converter lock-up. Eliminate the computer, and you'll have to make provision for lock-up.

 

Thanks for all the information everyone. I appreciate you all sharing your experience. It actually runs pretty good the way it is, a little rich when it's cold. Think I will leave well enough alone.

 

I always forget about the lockup. Never even crosses my mind because Ive always had the manual.

 

Sorry about that! I should have said, "Most guys I know," since that IS what most guys I know do in that situation.

Actually, 5.7, YOU are the reason I don't trade them off anymore. Years ago I read some of the stuff you said and did to these setups and I even got a successful setup together for one of my Buick 350s by using all LG4 parts.

Keep up the good work!