Questions re: 307 to 350/403

[Blew86442]

86' 442

I am thinking about swapping out a 307 to either a 350 or 403. My main question is, what is controlled by the computer that I would have to address without having the computer? Amenities like AC/ cruise/ lock up converter? I'm not worried about emissions or anything with the smog equipment. Thanks

 

[FE3X CLONE]

You'll need to run an aftermarket TCC lockup kit for the converter if you want it to lock/unlock automatically without the computer.

I have not seen anything definitive on the A/C control. I've heard that on the '87 models the A/C was somehow tied into the computer but on earlier models they used a switch. I believe this was for the compressor clutch disengage at WOT.

 

[442_olds]

Yes, it was controlled by the computer. On my '87 442, I looked for the cutout switch that was supposed to be above the gas pedal. There was none. Later on, I bought the CSM, and when I was reworking the wiring in the dash, I traced the schematic back, and found that there is a cutout switch in the ECM. I also found a page which states that during certain conditions, such as warm engine startup, high coolant temp, low idle speed, and when a signal is sent from the Throttle Position Sensor to the ECM indicating wide open throttle, the ECM cuts out the AC compressor. If you have access to a Chassis Service Manual, look at the schematic in the vehicle sensors and emissions controls to find the schematic. The part about the AC cutout is in the General AC information.

 

[Blew86442]

Thanks so far guys!

 

[DoubleV]

AC is controlled by computer but to bypass that function only requires splicing one wire to another ( which bypasses that relay located on the AC/heater module ). Using the CSM, it was very easy to figure out.

Cruise will still work without the computer too. Just need to ground 1 wire. Doesn't get much easier than that!

Keep in mind if you're building a mild engine, it can still run the computer just fine ( even if it's just a temporary thing ).

 

[Blew86442]

Thanks!

 

[Minion1186]

While we're on the discussion about it, Is there anything different from rewiring a/c in a normal VIN Y to a VIN 9? I ask because of the WOT cutout switch above the pedal whereas the Y's dont have that.

 

[442_olds]

As I noted above, the ECM on the 87 controls the AC cutout. That's why there is no switch above the gas pedal. Looking through the CSM, I can't see any difference in the wiring. In fact, the book illustrates the cutoff relay located by the blower motor and accumulator, and says for VIN Y or 9. There are some small differences in the schematic between the two, but the AC wiring looks the same. Can anyone else with a CSM verify this?

 

[DoubleV]

As I noted above, the ECM on the 87 controls the AC cutout. That's why there is no switch above the gas pedal. Looking through the CSM, I can't see any difference in the wiring. In fact, the book illustrates the cutoff relay located by the blower motor and accumulator, and says for VIN Y or 9. There are some small differences in the schematic between the two, but the AC wiring looks the same. Can anyone else with a CSM verify this?

Are you sure about that because for the 85's, the AC wiring is COMPLETELY different between the Y and the 9. I could very well be mistaken, but I recalled that being the same case with the 87's too. Yes, they do both have the cut-out relay by the blower motor, but other than that, they're very different.

Of course it should really make one wonder; if the ECM is controlling the AC compressor, why did they bother with the cutoff switch by the gas pedal on the Vin 9's? Why wasn't it just controlled by the ECM via the cutout relay whenever the ECM saw high TPS voltage? It's the little things like this that make you question the sanity of GM.

EDIT; Why the fvck are there links in my above post when I didn't put them in? :?