noob needs help with mileage - only 10 MPG!

A narrow A Body that vintage in decent mechanical condition and an auto tranny in normal driving should get 14-16 city and 16-18 hwy mpg easily. My 66 Dart w/a tired 225 and 3 spd manual gets 21 on the hwy if I drive easy.

If the fuel pump isn't leaking into the crankcase (already mentioned) and the timing is ok, and it runs well, you should do much better. I'm sure you have already checked out the auto choke when it is hot, to make sure the butterfly is open all the way. Those choke thermostat springs die with old age. Also, some of the 80s era had an electric heating element that was supposed to kick in and pull the choke off (stupid, eh?) so worth a check. A partially closed choke will sure burn more gas.

Does it have the original Carter carb, or did they bring the Holley over with the engine transplant? How about the rest of the smog stuff from 1980? Slants in the post-smog era were much worse; one of the nails in their coffin. The 74 Swinger with 225 and auto, 1 bbl Holley, PS,PB,AC I had never got much better than 15 to 16 on the hwy. If the smog set-up was carried over in the transplant, you have de-tuning and surgery to do. I think I recall the cam/valve timing on the smog models was a little different, and as they came from the factory, would never perform or get mileage like the 60s versions.

The Carter BBs were better for mileage. I found if you can locate a Carter BB made for the 170 Cu In, it will absolutely get better mileage with little noticeable performance difference in a non-smogged 60s A Body. It had a slightly smaller air horn and venturi. Whatever carb, they were simple. Get a kit and a new float and some carb soak and rebuild it; just pay attention to the drawing in the kit as you take it apart and lay out the pieces; the kit will have parts in it for other variations of the carb.

If that does no good, I'd look to the tranny. If it's slipping, if the torgue converter seals are leaking, if the pump is weak, if there is a crack in the shift body galleries or not locking up in high gear, you'll never get decent mileage. I've seen this happen in the older cars. Especially if the car is new to you, it may seem ok. See if you can find a 'vintage' mechanic who is still in business and isn't senile yet and have him check it out. It is my guess that is your problem. Sometime a shot of tranny tune-up will help the seals, at least for awhile..maybe...

It's hard to get a Slant to get 10 mpg even if it's running poorly - unless you like to race. In that case, the 'swap it for a big V-8' is good advice. If mileage is you main reason for having an A Body, keep your eyes open for one with a manual. They were not the best manual tranny ever, and hard to find parts for, but they were always good for a couple more mpg.

Good luck!

Captain Easy
:coffee2: