The question here is for my 1985 high top Ole Yellar Astro van build that I am swapping in a V8.If I could swap in a 355 sbc then check the gas mileage and then swap in a sbc 383 to compare that gas mileage,what would be the difference be??.

Details:TBI on both, using a roller cam on both which is This one:

GM PART # 14097395
CATEGORY: Engine Camshaft
PACK QTY: 1
CORE CHARGE: $0.00
GM LIST: $176.40
OUR PRICE: $146.76


DESCRIPTION: CAMSHAFT
Hydraulic Roller Design

This hydraulic roller design is used on the 383 truck. The duration at lash point in degrees (intake/exhaust) is 288/308; duration at .050" tappet lift (intake/exhaust) is 196/206; and maximum lift with 1.5:1 rocker ratio (intake/exhaust) is 431/451. Valve lash is zero/zero and lobe centerline is 109 degrees.

Steel heads for the 383 with a 195 intake runner or for a 355 180-185 range.

700R tranny,Ford 9" with 3.70's rear end gears,27" rear tires,cruise control on both,van's wt is in the range of 3,800 to 4,000 lbs,towing a 2750 lbs trailer not in O/D,towing threw PA mountains.

Thanks For Your Opinions In Advance,

Gary