kmckiou

Hi! I read Lars' excellent papers on tuning the Quadrajet and can conclude that my '73 454 has the stock jets and metering rods (77/48B primary and DA secondary). However, my gas mileage is terrible - about 5 mpg and I am wondering if it might be partially attributed to lower vacuum combined with a stock power piston spring.

My 454 has an aftermarket cam and it is pulling about 14" of vacuum at idle. I expect that a stock power piston spring would cause it to run rich. Can anyone (Lars?) recommend a better spring choice?

Also, any ideas on improving my gas mileage would be appreciated. I have rebuilt and adjusted the Q-jet and it seems to run pretty well, but 5 mpg is extremely poor gas mileage. I even thought about going to a leaner combination of jets and metering rods until I read Lars paper and determined they are stock. I have also checked the float level, the fuel shut off by the float-needle valve and the plugs in the bottom of the main carb body (no leaks!).

For reference, the carb number is 7043201.

Thanks,

- Kevin

comp

all is ajusted correctly ?

Boofers

One thing Lars told me about was adjusting the power piston stop plunger. Lower it 1/2 turn at a time. This will lean your mixture effectively at idle and cruise by allowing your rods to sit deeper in the jets. Drill and tap the metal plug in the top bowl cover that hides this adjustment.

comp

BigBlockk

If I remember right your power piston spring should be 2 less than your idle vacuum. So you should have something like a 12 in there. Then you tune the hight of the hanger.

Hope this helps.

BigBlockk

Later.....