350 Install, Couple Random Questions

[erikj17]

Can someone tell me the functions of the ECM in an 85 SS? I'm not positive, but I believe there was a lot of fancy emissions stuff on the original 305 carb. I'm putting in a 350 and want to minimize the unnecessary wiring. Problem is, I'm not positive what is necessary from the ECM - if anything. Can anyone point me in a direction there? I have yet to bother with a Haynes manual, as I've heard that the ECM definition is poor.

Also, anyone buy an exhaust kit from anywhere in particular with good success? I'm looking for true dual with a 700R4 transmission. Also, any specific crossmember you prefer?

Thanks for the help.

 

[joe_padavano]

Can someone tell me the functions of the ECM in an 85 SS? I'm not positive, but I believe there was a lot of fancy emissions stuff on the original 305 carb. I'm putting in a 350 and want to minimize the unnecessary wiring. Problem is, I'm not positive what is necessary from the ECM - if anything. Can anyone point me in a direction there? I have yet to bother with a Haynes manual, as I've heard that the ECM definition is poor.

Also, anyone buy an exhaust kit from anywhere in particular with good success? I'm looking for true dual with a 700R4 transmission. Also, any specific crossmember you prefer?

Thanks for the help.

Don't waste your money on a Haynes manual. Get a proper factory service manual. The ECM controls the mixture ratio on the primary side of the Qjet and the distributor advance curve. It also controls torque converter lockup, evaporative canister purge, A.I.R. system operation, EGR operation, and in some cars the idle speed and the A/C compressor clutch. You'd be wise not to start ripping out wires until you understand what each one does.

 

[erikj17]

The quadrajet is gone - I was under the impression that most of the wiring from the ECM was for that carburetor and was more emissions based. I have no intention of ripping out wires at random and plan on understanding what each does - my question was more for what functionality is no longer required with my new engine/carb install. I would prefer to not have a dozen connectors that no longer attach to anything cluttering up the engine bay now that the stock 305 and carb are gone. I have a feeling that no service manual will provide that information.

 

[gs dewd]

The quadrajet is gone - I was under the impression that most of the wiring from the ECM was for that carburetor and was more emissions based. I have no intention of ripping out wires at random and plan on understanding what each does - my question was more for what functionality is no longer required with my new engine/carb install. I would prefer to not have a dozen connectors that no longer attach to anything cluttering up the engine bay now that the stock 305 and carb are gone. I have a feeling that no service manual will provide that information.

Well if your not using the orig style carb then you need to make sure you swap out the dist. too. With one from a non computer controlled car. And you will need to find away to control tourqe converter lockup unless you swaping the trans also. If that is the case then you computer isn't controling anything. If it was controlling the wot switch on the a/c and you want to keep the a/c then you will need to find a way to hook up a wot switch for the a/c.

 

[megaladon6]

for an exhaust, try http://pypesexhaust.com/sys-mc.html

 

[erikj17]

The quadrajet is gone - I was under the impression that most of the wiring from the ECM was for that carburetor and was more emissions based. I have no intention of ripping out wires at random and plan on understanding what each does - my question was more for what functionality is no longer required with my new engine/carb install. I would prefer to not have a dozen connectors that no longer attach to anything cluttering up the engine bay now that the stock 305 and carb are gone. I have a feeling that no service manual will provide that information.

Well if your not using the orig style carb then you need to make sure you swap out the dist. too. With one from a non computer controlled car. And you will need to find away to control tourqe converter lockup unless you swaping the trans also. If that is the case then you computer isn't controling anything. If it was controlling the wot switch on the a/c and you want to keep the a/c then you will need to find a way to hook up a wot switch for the a/c.

This is exactly what I was looking for - thank you. And yes, the distributor is not the original one. The 200-4R transmission is being switched out for a 700R4, so torque converter lockup may still be "required." A friend of mine said that Painless Wiring actually offers a module for non-computer controlled cars to do the lockup.

wot = wide open throttle? The A/C in this car was removed prior to me getting it. Well, just the condensor and a couple lines are gone. Eventually I would like to re-install the A/C. Is there a way for me to check if the computer controlled anything in the A/C, or is it a given that it did?

Thanks again.

 

[megaladon6]

why are you switching to the 700? it's a good trans, but it's no better than the 200-4r. actually the 200 has a better 1st-2nd drop and a better over drive. granted you have to adjust the TV cable correctly but that takes about 2min. the only advantage that i see to a 700 is that a 4l65e is a direct replacement.

 

[gs dewd]

The quadrajet is gone - I was under the impression that most of the wiring from the ECM was for that carburetor and was more emissions based. I have no intention of ripping out wires at random and plan on understanding what each does - my question was more for what functionality is no longer required with my new engine/carb install. I would prefer to not have a dozen connectors that no longer attach to anything cluttering up the engine bay now that the stock 305 and carb are gone. I have a feeling that no service manual will provide that information.

Well if your not using the orig style carb then you need to make sure you swap out the dist. too. With one from a non computer controlled car. And you will need to find away to control tourqe converter lockup unless you swaping the trans also. If that is the case then you computer isn't controling anything. If it was controlling the wot switch on the a/c and you want to keep the a/c then you will need to find a way to hook up a wot switch for the a/c.

This is exactly what I was looking for - thank you. And yes, the distributor is not the original one. The 200-4R transmission is being switched out for a 700R4, so torque converter lockup may still be "required." A friend of mine said that Painless Wiring actually offers a module for non-computer controlled cars to do the lockup.

wot = wide open throttle? The A/C in this car was removed prior to me getting it. Well, just the condensor and a couple lines are gone. Eventually I would like to re-install the A/C. Is there a way for me to check if the computer controlled anything in the A/C, or is it a given that it did?

Thanks again.

I'll see if I can find a wiring diagram for you. All the comp controlled switch does is cut the compressor off when you go to wot(wide open throttle) IF your is comp controlled you should be able to just run a switch to the throttle linkage and controll it that way. Kinda just like a wot nitrous switch. Just use a normally closed switch instead of a normally open switch. But i'll check into that when I find a wire diagram and see if your car had it in the first place.

 

[erikj17]

why are you switching to the 700? it's a good trans, but it's no better than the 200-4r. actually the 200 has a better 1st-2nd drop and a better over drive. granted you have to adjust the TV cable correctly but that takes about 2min. the only advantage that i see to a 700 is that a 4l65e is a direct replacement.

I guess you could chalk this up to inexperience with it. I want a TH350, but I also want overdrive. I have a 94 caprice with an LT1/4L60E combo. I love it. In my opinion, one of the best cars ever built.

Because a 350 engine is going in, I figured a 4L60/700R4 would be the perfect complement. The 200-4R in the car right now is shot - it won't get out of 2nd gear. As much as I like the movie Days of Thunder, rolling 40mph at 4000RPM isn't quite my cup of tea. Without a doubt, transmissions are about as foreign to me as speaking Chinese. If I run 300-400 horsepower, isn't that too much for the 200-4R? Can they be built to be as beafy as the 700R4?

I appreciate any and all opinions. Thanks.

 

[custom442]

or... just turn the A/C off at WOT, no worries