BillGrissom
Well-Known Member
The easiest fix (better mileage and power) is to increase your spark advance until you get slight pinging slow at WOT (steep hill), then back off 2 deg. Forget the advance spec in the manual. A GM 8-pin HEI module & coil is fairly easy and cheap (junkyard) after you get a Mopar e-distributor.
The slant, like most straight 6's, has poor fuel distribution, with the center cylinders tending to run rich and the outers lean. A split manifold w/ individual carbs (like you ponder) would conceivably distribute better, but they are trickier to balance. 70's Honda motorcycles had 1 carb per cylinder and worked well, w/ great throttle response. A custom MPFI w/ balanced injectors would be the best, but a "fab your own" (pishta's posts).
My 69 Dart 225 got 22 mpg hwy regularly, and I do know how to measure mileage accurately. It always idled lean (several Holley 1920's), which drove me nuts but probably saved money. For any fuel system, smart to install an O2 sensor, so you aren't "flying blind". Weld in a bung next time you play with the exhaust pipe. You could even run a vacuum line from carb base to the cabin and make a controlled leak (w/ valve & filter) to lean it out on the highway and see what improvement you get. Small planes do that.
The slant, like most straight 6's, has poor fuel distribution, with the center cylinders tending to run rich and the outers lean. A split manifold w/ individual carbs (like you ponder) would conceivably distribute better, but they are trickier to balance. 70's Honda motorcycles had 1 carb per cylinder and worked well, w/ great throttle response. A custom MPFI w/ balanced injectors would be the best, but a "fab your own" (pishta's posts).
My 69 Dart 225 got 22 mpg hwy regularly, and I do know how to measure mileage accurately. It always idled lean (several Holley 1920's), which drove me nuts but probably saved money. For any fuel system, smart to install an O2 sensor, so you aren't "flying blind". Weld in a bung next time you play with the exhaust pipe. You could even run a vacuum line from carb base to the cabin and make a controlled leak (w/ valve & filter) to lean it out on the highway and see what improvement you get. Small planes do that.
