I have an opportunity to buy one of these specific E4MC Q-Jets and wanted to know if they had anything special about them compared to the standard ones. My car is a 1989 Caddy with the 140hp Olds 307 engine, wondering if it'll offer even the slightest in performance boosts.

 

I believe they are 800 cfm and have richer calibration than the VIN Y carb.

 

First, all the 307 carbs have a stop on the secondary air valves that limit them to only opening about 70 degrees instead of the normal 90 degrees. There is no universe in which an otherwise stock 307 will ever come close to using 800 CFM.

Second, the "calibration" is in the ECU, not the carb. The only other difference is the secondary metering rods, which can be swapped into the original carb in about 30 seconds.

Third, unless the carb matches the ECU, you are asking for trouble in getting the car to run right.

Fourth, the primary difference between the VIN Y and VIN 9 motors is the cam. Swapping the carb will have at best ZERO impact on performance (though your "butt dyno" will likely tell you there was an improvement since you put all that money and work into it... ).

 

Okay, so it would seem that swapping carbs wouldn't do very much of anything. What about switching out the secondary metering rods or modifying the secondaries so they open up to a full 90 degrees? Any improvements there?

 

Olds engineers were not stupid. The reason the secondary air valves are limited is because the 307 can't use any more airflow. If the secondaries open too much, the engine just bogs. Unless you have made other modifications to the engine that improve airflow (exhaust, cam, heads, intake) this is just a waste of time. The engine needs to work as a system, meaning all parts need to be matched. There is no easy, low hanging fruit here.

 

Gotcha. So just take this knowledge and store it in the back of my mind for now until I swap out for a 350.