My truck has a stock block and head.Hei conversion and one barrel carb.Currently the tach reads 2800 rpm at 65 mph.Around town the rpms are 1700 at 40 mph.The rear gear is a 3.55 with 235/75-15s.My question is "Where is the sweet spot in the rpm range for mileage?".Lower rpms are not always best for better mileage.Thanks in advance for any insight.

Mine develops the most torque at 2000 rpm (50 mph) but the sweet spot, most power is at 2500 rpm (60+ mph). I have lots of pedal to work with (very responsive with lots of punch) and the vacuum gauge stays pretty stable between 16 to 18".

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Aggressive Ted

http://cid-32f1e50ddb40a03c.photos.live ... %20Swinger


74 Swinger, 9.5 comp 254/.435 lift cam, 904, ram air, electric fans, 2.5" HP2 & FM70 ex, 1920 Holley#56jet, 2.76 8 3/4 Sure-Grip, 26" tires, 25+MPG

You should stick to 2500 rpm, that is were you have the best torque out of the engine, better response and manifold vacuum

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Martin Zappettini
1974 Dodge Polara RT 318cu.
1965 Valiant III Coronado Slant Six 6-Pack (soon!!)

One of the machinists I go to had mentioned something one day while I was visiting his shop, and he said the if you are dialing for mileage watch you torque band not your horsepower.... which would support everything I've seen/heard so far. So if you can do a dyno run, or even a G-Tech Run to see your torque curve, you can feasibly figure out the best ratio, tire size, etc... that would match your engine's "style".

-D.Idiot