base timing on chevy motors

Chuckman

Chuckman

Well-Known Member
Joined
Oct 9, 2005
Location
Huntersville
Anybody know of a reference site that has the REAL base timing settings for chevy EFI motors (93 TBI for instance from a Caprice). I have heard from 'reliable' sources everything from 0 to 6 degrees base. Yeah, I know that the ECM handles it when it goes closed loop, but when it knocks out, it still needs to be correct. Right now, I have given up on the correct base and have it set by ear / free idle with the jumper disconnected. And no, I dont have the donor to reference from. That the is run of the mill answer from the techs I talk to. Cant imagine that there isnt an easy answer for this, yet I have looked for good info for years.
Let the bashing/ opinions ensue...
 
I have a 90 tbi in my shop right now and the sticker under the hood says 0* base. But you are right, you can range it anywhere from 0 to 6.
 
What would be the defining characteristic? The only thing physically in the motor that I could think of would be the cam. I know that the books rate the 'car' motors differently than the 'truck/van' motors in HP/TQ, so what gives. Do you honestly need that dang setting from the actual vehicle? This was from a Caprice cop car and I've have had no luck in finding the base setting on this motor. When it goes into open loop, or when its warming up, it seems like its rich (gives you an instant headache at the pipes). But it idles smoothest/fastest at this setting with the setting connector unhooked. Cant remember where its set now since I have tried 0~6 with various results.
 
Do you have a way to read the ECM real time ? you need to find out if the engine coolant temp sensor is reading correctly. if it isn't communicating the ECM defaults to -40* and it'll run VERY rich until ECM times out and switches to closed loop ( there is another part of this I am drawing a blank on at this time, but check the engine coolant temp sensor)
 
most of the TBIs are 0 deg base. haynes/chiltons should list it anyways. I have my heep set to 6 but the prom has been set to reflect that...

you can check thirdgen.org in the TBI or DIY-PROM section..
 
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