When is it necessary to swap an ECM after mods?


For example, say I have a 305 TPI now. Then I put in a 350 TPI. Would it be necessary to swap in a different ECM or just the PROM?

Or say someone put in a 383 to replace their 305 or 350. Would they need to replace their ECM, the PROM. Or just keep it all and reprogram?

 

Regarding your '90, going from a stock 305 to a stock 350 (including injectors), you could likely get away with the 305 PROM. It would be best to swap in a 350 PROM. Note that you wouldn't want to swap just the PROM, but the entire MEMCAL. As it also contains the knock filter (ESC module).

Now going to a 383 is a bit different. usually because there are other upgrades done at the same time. Such as heads, cam, and larger injectors. If the stock heads and cam are used, along with 24#/hr injectors, most likely could get away with a stock PROM.

But all in all, it will be better with some tuning. Even stock engines can be tuned for better performance.

RBob.