whats the best engine for both performance and mileage??
I found an almost rust free 70 dart and am trying to do a cost effective mild restoration. Planning an overdrive automatic and would like good power. I was thinking about stroking a 360 but would I be better off with a 318. I can get the 318 engine and trans out of a 91 pickup for nothing.
Any suggestions and what kind of MPG can I get with various senerios. PS I was planning a 3.55 Posi.
Thanks
Greg Wise
Greg;
First up is great idea on a O.D. trans. The 3.55 gear X the .69 (MoPar trans) gear final ratio equals a final feel gear ratio of 2.4495. (2.45) This may be a bit to long legged for you.
You want the cam to cruise in a certain RPM range that works well with the gear ratio. (Also vehicle weight and other items, but, not so needed at the moment.) Lets look at other gear ratio's.
Now this may sound crazy, but via the math (Axle ratio multiplied by O.D. ratio equals final drive feel ratio) A set of 4.30 gears and the O.D. ratio of .69 equals 2.967. (2.97) - 4.10 X .69 = 2.82. This is a good ratio for stock diameter tire size and a excellent cruise ratio with use of a upgraded cam. Going to a taller tire should be kept to a min.
With that gear ratio, even a small cam will work.
And many will think this wacky, but be it headers or exhaust manifolds, a cam like Comp's 265DEH in a 9.0-1 ratio 318 will make right about 280 - 300 HP depending on carb, intake and exhaust.
The biggest issue for you right now is the compression ratio of the engine.
The Magnum should be a 9.0-1. What it actually spec's out to be I do not know. IDK, if milling the heads for more ratio is OK with you, but I think you could use it no matter what.
The nice thing is it is a roller engine. Stay with a roller cam and around 211 - 218 intake duration and more for exhaust.
Also, are you going to use exhaust manifolds or headers?