And then you've got guys like me... when federal and cardone closed out inventory I bought a couple dozen refurbished ecms at a good price. I know, horror stories on refurb. I figure if 1 in 12 worked right I'm still ahead on money if one ever did go bad for whatever reason.
Quick 4barrel carb ID
- Thread starter pagrunt
- Start date
Just about EVERY GM ECM was rebuilt too, so it pretty much didn't matter where you got them.
Components that were usually rebuilt/refurbished for G-bodies when getting replacements from GM...
Alternators
Starters
ECM boxes (still needed to put in your chip)
Back to the E-carburetors for a minute...I speak mostly in generalities here because as the E-series carbs went along, they learned a whole ton about how they acted in the real world so updates to these carbs were done frequently, almost year to year, and sometimes in the middle of the production run. So you can't say "always" for the most part.
As mentioned, the Olds carbs are E4MCs while the Chevies are E4MEs. Adjustments to tune them are different as the Chevy carbs are normally 4-point adjustment carbs where the Olds was 2-point (85-up VIN Y) and 3-point (VIN 9) adjustment carbs. The point number really wasn't the number of adjustments in reality, according to GM. They look at it from a manufacturing technique standpoint. Which is kinda stupid, but well....GM.
There are 4 places that need to be preset on a E-Qjet. The air bleed valve, the rich stop, lean stop, and the idle air mixing screws. Using specialized tools, you rebuild the carb and things get set in the ballpark so when the carb is placed on the car, it should take a few tweaks to get it set where it needs to be. Rich and lean stops were set during assembly.
The Chevy carbs were usually 4-point adjustments. This entails using the air bleed valve AND the idle air mixing screws to adjust the dwell. First you adjust the air bleed valve, then the idle air mixing screws. And if further tweaks to be made, go back to the air bleed valve again, then the screws, until you get it dialed in. Little tweaks are usually all that's needed to get a good needle movement. So don't get all twisty with it.
The Olds VIN 9 carbs were typically 3-point adjustments. The way to tell is on top of the air bleed valve, a letter is stamped in to indicate a 3-point air bleed valve. You would not need to adjust it for dwell once it is preset. You would use only the idle air mixing screws to adjust the dwell. I do know they have metric O-rings on the air bleed valve, and GM goes to great lengths to tell you that replacing those O-rings HAS to be done with metric sized rings (included with the GM carb rebuild kits)
The 2-points were like the 3-points, except the rich stop was "built in", so there's no provision for even adjusting the rich stop. So, there you go. You still would dial in the dwell with the idle mixture screws.
And as always, once everything else is dialed in, adjust your engine curb idle speed last (unless something in the procedure tells you differently).
Components that were usually rebuilt/refurbished for G-bodies when getting replacements from GM...
Alternators
Starters
ECM boxes (still needed to put in your chip)
Back to the E-carburetors for a minute...I speak mostly in generalities here because as the E-series carbs went along, they learned a whole ton about how they acted in the real world so updates to these carbs were done frequently, almost year to year, and sometimes in the middle of the production run. So you can't say "always" for the most part.
As mentioned, the Olds carbs are E4MCs while the Chevies are E4MEs. Adjustments to tune them are different as the Chevy carbs are normally 4-point adjustment carbs where the Olds was 2-point (85-up VIN Y) and 3-point (VIN 9) adjustment carbs. The point number really wasn't the number of adjustments in reality, according to GM. They look at it from a manufacturing technique standpoint. Which is kinda stupid, but well....GM.
There are 4 places that need to be preset on a E-Qjet. The air bleed valve, the rich stop, lean stop, and the idle air mixing screws. Using specialized tools, you rebuild the carb and things get set in the ballpark so when the carb is placed on the car, it should take a few tweaks to get it set where it needs to be. Rich and lean stops were set during assembly.
The Chevy carbs were usually 4-point adjustments. This entails using the air bleed valve AND the idle air mixing screws to adjust the dwell. First you adjust the air bleed valve, then the idle air mixing screws. And if further tweaks to be made, go back to the air bleed valve again, then the screws, until you get it dialed in. Little tweaks are usually all that's needed to get a good needle movement. So don't get all twisty with it.
The Olds VIN 9 carbs were typically 3-point adjustments. The way to tell is on top of the air bleed valve, a letter is stamped in to indicate a 3-point air bleed valve. You would not need to adjust it for dwell once it is preset. You would use only the idle air mixing screws to adjust the dwell. I do know they have metric O-rings on the air bleed valve, and GM goes to great lengths to tell you that replacing those O-rings HAS to be done with metric sized rings (included with the GM carb rebuild kits)
The 2-points were like the 3-points, except the rich stop was "built in", so there's no provision for even adjusting the rich stop. So, there you go. You still would dial in the dwell with the idle mixture screws.
And as always, once everything else is dialed in, adjust your engine curb idle speed last (unless something in the procedure tells you differently).
For sure, I agree with that standpoint.
It’s more the extra money needing to be spent on parts meant for CCC like I mentioned before.
That and just more electrical wiring to deal with, and with age means I will need to have it replaced.
I would guarantee you that the 12 you have originally just had a bad chip. What caused a chip to go bad was a voltage spike like jump starting or bad alternator. I replaced more chips at the dealership do to a spike but never replaced the ecm.
Last edited:
The CCC cars were few and far between up here in Canada so we basically only saw them on 86 through 90 cars. Other than US made special models like the H/O or 442, nothing pre 86. I know one mechanic who I would actually trust to rebuild and calibrate the CCC Quadrajet, my Boss's Uncle Randy who is basically retired. He rebuilt the factory carb on my Boss's 88 Monte Carlo SS, it runs great. Of course if I find a nice H/O or 442, I would do it myself.
Without computer input the electronic Qjet defaults to full rich mode. With the air fuel mixture solenoid, off is rich and on is lean. That way in an event of a hard CCC failure the engine won't burn up.
Old used OBD1 scanners can be had for pretty cheap such as the Alltest Brainmasters. CCC systems really hate vacuum leaks, which aren't good for any engine.
Last edited:
Similar threads
