73 Plymouth Duster
Well-Known Member
Hey guys so I have been working on my 73 duster for about 16 months and have been driving it recently for the past 2 months getting the bugs worked out of it, I have just recently gotten the kickdown hooked up right and adjusted and other odds and ends. I also took my GPS with me to check the speedo and odom. the speedometer is about 6% off and the odometer is about 11% off both too optimistic it will say 63mph and traveled 30 miles when in fact it is like 60 mph and 26.8 miles miles. That's a problem in itself that I need solved. I am planning on getting a new speedo gear to match the odometer then just deal with the speedometer being off.
Primary question: I just filled up today and my odometer said I went 130 miles so about 118 miles realistically...and it took 12.5 gallons to fill it. So I am shooting under 10mpg in a 318!?! I'll list the engine specs below and let you guys have a go at what you think I can do to increase mpg.
318 with new run of the mill pistons (put in when I bought car) checked clearances and torqued bolts and called it good. they are about
-8.5:1 compression
-bored .030 over
-Comp Cam 262, so a bit spicy.
-dual plane air gap high rise intake
-holley 650 cfm carb (too big?)
-not sure if they are "x" or "j" heads but they were hardened seats, valve job which included 2.02 intake valves and stock exhaust valves. decked heads .01
-used .040 head gasket (not .028)
-shorty headers
-dual exhaust with balancer pipe in between (h-pipe)
-took to Tom's performance in town, who ended up ripping me off a bit but they re-jetted carb from 64's to 66's I believe. and they "drilled restrictors in accelerator pump" and plugged vacuum advance. (all for more HP) double checked timing to 14 initial and 35 all in like I had it. A bit high I know but that's where it just seems to like it.
So since then I have hooked the vacuum advance back up to a ported spot on my carb. and I run regular gas with ethanol, tried non-ethonal premium and didn't notice much difference. Any guesses on why my milage sucks haha my park brake isn't on but I feel like it's something that obvious, thing sure does sound great though. and with 3.55 posi it likes to get up and go.
Primary question: I just filled up today and my odometer said I went 130 miles so about 118 miles realistically...and it took 12.5 gallons to fill it. So I am shooting under 10mpg in a 318!?! I'll list the engine specs below and let you guys have a go at what you think I can do to increase mpg.
318 with new run of the mill pistons (put in when I bought car) checked clearances and torqued bolts and called it good. they are about
-8.5:1 compression
-bored .030 over
-Comp Cam 262, so a bit spicy.
-dual plane air gap high rise intake
-holley 650 cfm carb (too big?)
-not sure if they are "x" or "j" heads but they were hardened seats, valve job which included 2.02 intake valves and stock exhaust valves. decked heads .01
-used .040 head gasket (not .028)
-shorty headers
-dual exhaust with balancer pipe in between (h-pipe)
-took to Tom's performance in town, who ended up ripping me off a bit but they re-jetted carb from 64's to 66's I believe. and they "drilled restrictors in accelerator pump" and plugged vacuum advance. (all for more HP) double checked timing to 14 initial and 35 all in like I had it. A bit high I know but that's where it just seems to like it.
So since then I have hooked the vacuum advance back up to a ported spot on my carb. and I run regular gas with ethanol, tried non-ethonal premium and didn't notice much difference. Any guesses on why my milage sucks haha my park brake isn't on but I feel like it's something that obvious, thing sure does sound great though. and with 3.55 posi it likes to get up and go.