rorrapalooza

Ive got an 84 corvette with a few mods;
basically just a renegade and 1.6 roller rockers

I was wondering at what point I would have to go to another ECM
could I get away with AFR 180 cc heads, ARH true duals and a mild roller cam, for example the Comp XFI252?

could I at least get away with the heads and headers with the stock ecm?


If I do go with a new ecm, what should I do? it seems like theres so many options out there: 7747 ECM with HAM board, EBL Flash (but it looks like I would have to loose the oil temp guage that route), Ostrich, Prominator, speedreader, custom chip...
I dont really get what the differences between these really are

JimLentz

Your best bet is to find someone that can burn PROMs and tune your car on a dyno.

Tom400CFI

Very very few people have tuned or are able to tune the '84 ECM.




Personally, I would TRY to make it work first, with the original ECM/tuning because that is basically free. With a mild cam, which you said you're using, I think it will work O.K. with fuel injector sizing, pressure and a vacuum referenced FPR.

I was a ble to run a SBC 400, 224/234 (.050) cam, fully ported intake, headers, rockers...all on a stock 305 ECM/Tune. The results were;
Low-mid 13's/105ish in the 1/4
Stock like drivability and idle
24+ mpg highway.

I think those results are better than "good enough" and they were obtained through nothing more than injector sizing, pressure tinkering and the vacuum referenced FPR.

When things get unmanageable with the stock tune are when you change the shape of the tq curve too radically...and that happens my moving too far from stock cam duration. As long as you keep the cam close to stock, the shape of the tq curve will remain similar to stock...only more so, which is pretty manageable with more fuel across the board at WOT.


If I were you and I couldn't get acceptable performance from the stock ECM and that "mechanical" kind of tuning, then I would go with the 7747 ECM as that has been a common, well traveled path -no need to reinvent the wheel.

Red1990VT

Sounds like you still have the original injectors and throttle bodies...if that's the case you can probably keep the OEM ECM and PROM. You've apparently increased the volumetric efficiency of the engine with the new manifold and heads, and might still fall within the ability of the OEM computer and calibration to handle it. The Crossfire system does have Block Learn Mode that allows for variations around the VE values set in the PROM. At some point you might end up needing more correction than the BLM can handle, but you'd be able to read the BLM table and see if you've reached it's limits in any of the cells. If so, that might be the time to think about a recalibration. If not, you're good to go, the system will handle the mods you made.

Buccaneer

Like Tom, I think this cam will work OK for you without moving to the 1227747 or 1228746 ECM. The dur@.050 looks good and close to stock, once you get farther away from that area, the worse it gets for using a stock ECM. What you don't want to do is put a big overlap cam with a stock ECM. The MAP sensor WILL wig out and start bouncing around and the motor will not run properly. The 180 heads should be fine as well. I would take a look at the A/F on a dyno if possible in a controlled environment and see how it's doing, just don't run it lean at WOT. 12.6ish WOT is a good number as a rule of thumb goes. It may go rich at tip in and then start going lean, that's what you need to know and go from there. Good luck with your project and post up the results.