Fox T-Bird/Cougar Forums  

X2
I just rebuilt my 302 w/no serious mods to upgrade the fuel injection or computer still running 19lbers but I did want to do a 351 block if that were the case was to go carb the difference to me was about 500 for a carb and intake to a completely upgraded injection system some even recommend if your going to spend the money on fuel injection to go completely after market. But like some said its his car as long as he’s happy.

No it won't be fine. The non-HO speed density computer would puke on the HO cam, the injector firing order would be wrong, and if you upgraded to 19-lb injectors the non-HO computer (which is calibrated for 14-lb injectors) would make the car run way rich.

If you want to keep the stock, non-HO computer, you can use all the HO parts EXCEPT the cam and injectors.

the problem is that you will force the system to run into what's called, an "Adaptive Strategy " condition. When you check SD/MA EEC-IV systems ECM pinout at the ECM ('86-'93), HO and non-HO, with the exception of the '91-'93 T-Bird MA system (similar to '94-'95 Mustang systems).....all have the same arrangement.

If you change the injector pins, the system will adjust fuel trim on a bank 1 injector, based on the B1 O2 readings, for an injector that is now connected in bank 2, and vice versa........for example, using their layout you have a 154.... firing order

1 - 5 - 4 - 2 - 6 - 3 - 7 - 8 which divided by bank (B1 = cyl 1-4 and B2 = cyl. 5-8) would be.....

B1-B2-B1-B1-B2-B1-B2-B2......now you switch the injector wiring .....5-to-3, 4-to-7, 3-to-5 and 7-to-4......to ensure the injectors firing order......

1 - 3 - 7 - 2 - 6 - 5 - 4 - 8 ......which should be.....

B1-B1-B2-B1-B2-B2-B1-B2.....when you lay it out by bank, but it's not.... what happens to the "logic".....

EXAMPLE: B1 O2 reads RICH condition and adjusts (shortens) fuel trim pulse for B1 injectors (1-4)

1. System shortens B1 fuel trim, but since #3 and #4 are now in B2 (5 and 7).....such a change will not be enough since the O2 in B1 will read half of the fuel trim effect (2 injectors), so the system continues to shorten fuel trim even further.....looking for a change in B1 AF readings....but wait, there's more......The fuel pulse tpuppies for B1 will affect B2 O2 readings (#3 and #4 are in B2)....causing B2 readings to be LEAN...

2. The system then determines it needs to lengthen B2 fuel pulse due to #1 above, and it does for the 5-8 injectors, but since #5 and #7 are now in B1, the adjustment for B2 affects B1 O2 readings....causing B1 to continue to read RICH. And since B2 O2 readings have not changed that much, the system continues to lengthen B2 fuel trim pulse.........

For crying out loud, the system is going crazy..... ...(I know I am explaining this.....)...and will eventually cause a ....condition from the ECM.

It's like having a normal EEC-IV system, but installing the LH O2 sensor to the RH connector and vice versa.....the system will adjust injectors 1-4 based on the AF readings from injectors 5-8......and ....I've seen a few of those cases as well......

there's nothing "HO" about the crank and rods.

Gotta disagree Carm.  It CAN work.....
While using an HO computer with the HO cam would be the proper thing to do running the SO computer for a while WITH AN ADJUSTABLE FUEL PRESSURE REGULATOR would work.  If he were to do so repinning the injectors would be a no-no.  Leave th injector wiring alone.
Here's a write-up explaining why.

The only thing i want thats not EFI is a 1967 to 1970 mercury cougar with side pipes painted salt flats and a big blower sticking out of the hood oh wait and a Pantera and thats about it.

Do you work on Carb cars a lot yourself?