Re: 304/290/200R4 - now V8 Fuel Mileage

[farna@xxxxxxx]

I'd think the discussion WAS in the right direction. I explained WHY you need a low fisrt gear and/or a broad range of gears when using a high axle ratio. Just dropping the ratio won't necessarily increase economy, it can hurt. So gearing from the tranny back is an issue. You mention T-4/SR-4 with numerically low axle, but that applies to ALL transmission choices. The five and six speed transmissions usually go lower in the early gears rather than higher in the hig gears. Otherwise you have to lower the rear axle ratio instead of making it higher.

You forgot the AW-4. It would be fine behind a stock or even mild 304 (small 4V and RV cam), even a stock 360, especially if built for economy. It can also be beefed up like the 2004R would need. I would put a stock AW-4 behind a 360 before a stock 2004R, but I'm familair with the AW-4. It handles my 4.6L stroker (240 hp/300 lb-ft NET, which equates to ~300-310 hp/375-400 lb-ft gross) easily, and many on the Strokers Yahoo group run that trans in rock crawlers and mud rigs without beefing up. It can be beefed up, but you'll end up with a $2500 rebuild. I forget the name of the company who builds them for high power. I don't think the 2004R will handle that in stock trim, but is much cheaper to have built for power. 

The cam, carburetion, and weight of the Caprice all come into play. We had a mid 70s (77 or 78) Caprice as well. It was made as light as practical, definitely lighter than an early 70s model. Wasn't that an electronic Q-jet, much like the Eagle BBD, or did those not come out until 79-80? I never got under the hood of dad's Caprice, he only kept it about three years, didn't care much for it. 



On May 9, 2005 Dwight Southerland wrote:

> I have followed this whole thread with some interest to see what input would be shared.  I feel like the original direction of the thread was abandoned somewhere along the way.  I would personally like to hear input on the subject of increasing fuel mileage on an AMC V8 powered car using modern technology and parts that are available.
> 
> What seems to be reasonable options for manual transmission selection would fall into these choices:
>      1) Use an AMC T-5.
>      2) Adapt a Ford T-5.
>      3) Use a T-4 or SR-4 with numerically low rear axle ratio.
>      4) Adapt a GM T-5.
>      5) Adapt a Richmond 5 or 6 speed.
> 
> For Automatic transmissions;
>      1) Adapt a GM 700R4
>      2) Adapt a GM 200R4
>      3) Adapt a MoPar 500 or 518 series.
> 
> In all the cases above, rear axle ratio selection for the body/engine combination would be a factor to consider.
> 
> Then there is always the carburetor/camshaft/engine combination that comes into play.  And, of course, fuel injection can be discussed.
> 
> I suppose what I am asking for is input that can be accumulated for all to see and review in one place.  Maybe it could be submitted to the AMC Forums site and othere liek the AMCyclopedia site for referenece information.  Experiential information from those who have done the work would be especially valuable, and of course the cost.
> 
> 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 exhaiust 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 that good, can't we?
> 
> Let the input begin.
> 
> Dwight Southerland
> 
> '67 Rogue 360/727 w/2.87 gears. 18 mpg.
> 
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