383 VS 355 gas mileage??.

[1gary]

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

[bigdude]

5-10 mpg difference

[rumrumm]

My first inclination is to say the 355 would get better mileage. But it depends which one works most efficiently pulling the weight of the van. It is possible that a 355 that is working harder to move the van could use more gas than a 383 that is working more efficiently.

[1gary]

My first inclination is to say the 355 would get better mileage. But it depends which one works most efficiently pulling the weight of the van. It is possible that a 355 that is working harder to move the van could use more gas than a 383 that is working more efficiently.

Yepper-my thoughts too.But if it was just a small difference it "might" worth building a 383 for the extra torque.

[pat mccarthy]

under a load the 383. that cam is not far off a build 355 i did last fall were we had a custom erson roller ground and the pbm heads some what like gm v tech s they just do not crack .you have to watch with the throttle bodys if your going to use one.they will not take any cam they need to idle low .the map get out of wack then its dumping fuel out the tails and sound like a top fueler that 395 cam is used the the boats as well i used one in a mild street engine in a big car

[1gary]

Pat-here is a interesting read that awhile back I bookmarked.

http://www.tbichips.com/truckmods.htm