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

[farna@xxxxxxx]

My experience is about the same re torque peak. With the 3.08 axle my 4.6L cruised around 75 at 1600 rpm -- wasn't enough. Could be because of the cam I have though. Right now it cruises best at around 2000 rpm, which puts me right at 65 mph. At 2400 rpm I'm running 76. The 4.0L EFI system enrichens the fuel mixture noticecably at 2500 rpm. I generally cruise at 2200-2400 (70-75 mph) for that reason. 3.31 gears would put me more where I want to be as far as cruising speed. I could also drop to a 206/65R16 tire, which would look a bit better and be just a bit shorter diameter than the 205/70R15 I run now. 


On May 9, 2005 Tom Jennings wrote:

> On Mon, 9 May 2005, Sandwich Maker wrote:
> 
> I find this thread interesting too (and sorry if I helped it veer
> off) it all applies to all AMC motors.
> 
> > 'lugging' it is not a good idea.
> >
> > generally, your engine will be most efficient near its torque peak.
> > if you want great highway mileage, you want a cam that moves that peak
> > down toward your highway rpm.
> 
> As I see it, there's three things in tension: lower RPMs keeps
> frictional losses low, but you must have enough to makde decent
> torque and HP.  1600 rpm sounds great, but it's impractical to
> make HP there. 2000 - 2500 is probably a good target RPM for
> torque peak, probably line up all the hard parts
> (trans/OD/axle/tires) then have a cam ground to put it spot on the
> target RPM/MPH.
> 
> But first you can take really big hints from what the factory did;
> little americans with manual trans and steep axles, see where
> those cams are ground and start there.
> 
> Somewhere I made a big table of all the AMC six cam factory grinds
> (60's - 70's) but I can't find it!
> 
> 
> 
> 
> 
> .


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