non Buick Quadrajet auto vs. manual trans. part numberquestion

Hello, I have a stock 1973 Chevelle SS L48 (350 4v) M20 4 speed manual trans. The "Chevrolet By the Numbers 1970-1975" publication states that the correct Quadrajet carburetor for my car would be a 7043203. However, the carburetor on my car is a 7043202. By my observations based on how original the car is, I'd imagine that the carb is original, the attaching bolts, rear vacuum line for the power brakes and such, all look undisturbed and match the general patina of the rest of the engine.

I'd like to know the differences between the automatic version (7043202) and the manual trans version (7043203) of these 2 carburetors. If anyone has the specifics of the manual version 7043203 and could post them, then I can see if my carb has those things (like the primary jets, primary metering rods, Idle cam specs, Idle stop solenoid) and maybe my carb was incorrectly numbered from the factory? Thanks.

 

I asked some other Quadrajet guys, and I am told that the jetting and rods were the same between the two. But there may be some difference in the linkages. I have several 3202 carb cores on my shelf, but no 3203's. Online photos I found looked like linkages are the same.

I realize I am not much help here, but did want to share what information I had available. As with many quadrajets, the difference in current market value and in set up is just a difference of an original number stamp.

 

Kevin,

Just an observation here. I run 1970 automatic Q-jet on a car with manual transmission (since the original Q-jet is long gone). The only difference listed in the Chassis Manual between the two is in the primary and secondary vacuum break adjustments, and the idle speed. Otherwise exactly the same. Also interesting is that for the Stage 1 engine the Q-jet is the same regardless of automatic or manual transmission. Would be interesting to see similar observations on the Chivvy application.

 

thanks guys, this is very helpful.

 

I would post this question on my Forum. There is at least one Forum member who has a master catalog showing what jets and metering rods were used in factory production Q-jets by part number.

http://www.cliffshighperformance.com/simplemachinesforum/

 

Thanks Cliff and thanks to Carmantx, I saw that he posted out for me on your forum. Interesting about M/T cars running leaner than A/T cars per your forum member.

 

For the most part the same basic applications manual trans vs auto, the manual trans carbs will be slightly leaner on the jet/rod combination. I suspect having a torque converter and additional engine load plus torque multiplication at lower rpm's required a tad more fuel from the carburetor to make the engine happy. At least that's the best guess I have as to why we see this on a lot of manual trans vs auto carburetors used on the same HP engines/same year......Cliff

 

Check out the distributor spark curve. Manual trannys are more subject to engine lugging conditions just by their nature. So.....
1. To avoid detonation, be careful about too fast of a mechanical advance curve on a stick.
2. For drivability, I would rather have equal or richer jetting as an auto tyranny so the engine would be less apt to die on takeoff, and to avoid the detonation prone lugging mentioned above.
3. I saw the specs on an early 327 that had richer jets with a stick. I don't remember the source, but I still would consider all the above conditions and never risk being lean at wide open throttle, especially using pump gas with alcohol in todays crappie gas and less than stellar fuel supply with stock lines and pump.
4. What could possibly go wrong with a jet richer anyway? Let the apt adjustment get the fuel mileage you want.