V-8 Milage

["Bruce Hevner" <scramblr@xxxxxxxxxxx>]

>I have always been intrigued by my Dad's '86 Caprice which had a 305
carbureted (Q-Jet) with a >700R4, a 2.29 rear axle ratio, weighing 4400 lbs.
would pull down 26 MPG on the highway at 75 mph.  >This is what I know about
that engine: Bore/stroke is similar to a 304 AMC (3.736" x 3.48"), heads
>would flow around 200 CFM at .400" valve lift on the intake and around 145
CFM on the exhaust at >.400" valve lift (1.84" intake valve, 1.500" exhaust
valve), about 8.5:1 compression, .357"/.373" >lift camshaft (176 degrees
intake @ .050", 194 degrees exhaust @ .050", 109 degree lobe >separation,
installed at 106 ATC), stock cast iron exhaust manifolds with a single 2.25"
exhaust >pipe and catalytic converter.  The engine would literally loaf at
1700 RPM on the highway, yet >still have enough power to be satisfactory to
drive.  Surely we AMCers can do at least t

I did a little experiment with kinda the same type thing. I had an 86
Caprice Estate Wagon. I jerked out the 305 and tricked up a 350. Here's what
I did. Most of this would apply to an AMC too although you might have
trouble coming up with the same parts.
 I decked the block so the "Squish" was .035. I used TRW flat pistons &
dished them in a "D" shape to match the combustion chamber and to achieve a
true 8.5 ratio.
  I used 305 2-bbl heads that used 1.720 intake and 1.5 exhaust valves. I
used an Isky Mile-A-More cam (VERY short timing). The whole engine was built
with 4000 max RPM in mind. I had the trans rebuilt and shortened up the
shift points to 4200 max.
 I installed a crank scraper to keep the oil off the rotating assembly.
 I hit it pretty close, you could feel the power start falling off about
3800. The thing had FANTASTIC throttle response and would actually turn the
tires a few times from a dead stop. 
I used Michelin "energy" 225x15 tires (supposed to give better mileage).
 On the hwy (loaded 4 adults) it would get 19-21 MPG,,, at 85 MPH!!! If I
slowed to 65 it jumped on up to 23-24. Around town 18-19 was about it. But
as above,, this thing was a BEAST weighing 4400 lbs! So essentially I had
the power of a 350 with the mileage of a 305. It had 235k on the clock (110
on my motor) when the rear gear went south and I sold it.
Bruce Hevner

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