I have a 351w with a torquer cam rated up to 4500 rpms and the truck avenger carb. I'm running 33s my axle ratio is 2.73 on a 1-1 to the axles doing 55mph my motors runs 1500rpms. For over all road economy town/hwy,
should i be looking at installing 373s

I have a 351w with a torquer cam rated up to 4500 rpms and the truck avenger carb. I'm running 33s my axle ratio is 2.73 on a 1-1 to the axles doing 55mph my motors runs 1500rpms. For over all road economy town/hwy,
should i be looking at installing 373s

3.73s will be ok without overdrive (2000rpm at 55mph), you could probably go with 4.11s.

Use a calculator and figure out it out for yourself:

http://www.4lo.com/calc/gearratio.htm

I'd look at what your torque output is at 1500 rpm. If your motor is making enough power to move you down the road, you'll get better fuel economy the lower you can rev it. Think of the displacement of your motor (351 cubic inches) multiplied by the RPM. At 3000 rpm your motor is inhaling twice as much air as it is at 1500 rpm, and at 1500 rpm it's inhaling the same amount of air as an engine half it's size at 3000 rpm. I hope I'm making sense.

My step-dad had a 1988 5.0 notch with 2.73s and a 5-speed. He got 24 mpg daily driving half highway half suburban roads; and all because the revs were so low and the motor had enough torque to keep the car moving.

:confused:Its in jeep so its a brick. I've shaved alot of weight off it it only weighs 2700 or maybe even less. I'm lookin at 37's in the future so i was just trying to figure out what a good RPM constant is at 55 but also get the best i can in town. I'm not worried about crawler speed because I have a New process 435 and a stock dana 300. I was thinking that 2000 rpms would be ideal for 55mph. But are you saying that the 1500 would be good for this set up? I've degreed the cam 4% advance and its a performer intake so its rated 0 to 5500 rpms. But the Cams top rating is 4500. Basically My question is: Is 2000 the ideal running rpm for the 351w with this set up.
Using your math. I took 351 x 1000 through 4000 devided by 4 and got an average of 2500 rpms. So i'm thinking that out of fuel and air delivery 2500 rpms would be my most efficient at 55 mph giving that i dont ever go over that speed. RIGHT?

That's not what my math was.

My math suggests that a 351 cubic inch motor is drawing as much air at 1500 rpm as a 175.5 cubic inch motor at 3000 rpm. That would mean that by keeping your revs down, you are drawing far less air. By keeping the revs down, you are getting better fuel economy, provided your motor has enough torque to push you down the road.

If you are looking to find the peak power output of your motor, it's not likely at 2000 or 1500 revs. And you don't want peak power at cruising speeds. If you're asking if your motor needs more revs to get more power, the answer is likely yes. If you're asking if you can get better fuel economy by reving higher, the answer is likely no.

so do you actually drive at 55mph?
here the normal highway speed is closer to 70 mph

no mention of what transmission you have...

That's not what my math was.

My math suggests that a 351 cubic inch motor is drawing as much air at 1500 rpm as a 175.5 cubic inch motor at 3000 rpm. That would mean that by keeping your revs down, you are drawing far less air. By keeping the revs down, you are getting better fuel economy, provided your motor has enough torque to push you down the road.

If you are looking to find the peak power output of your motor, it's not likely at 2000 or 1500 revs. And you don't want peak power at cruising speeds. If you're asking if your motor needs more revs to get more power, the answer is likely yes. If you're asking if you can get better fuel economy by reving higher, the answer is likely no.

if you live in the desert where it is dead flat then 1500rpm at 55 would be ok
anywhere with hills would suck really bad unless you have a comfortable gear to downshift into

I'm running a Np 435. First gear is out except for crawling.

if you live in the desert where it is dead flat then 1500rpm at 55 would be ok
anywhere with hills would suck really bad unless you have a comfortable gear to downshift into
Yeah, or if your motor is making enough torque at that RPM, you would be just fine. It's about torque and where you develop it.

Pit bull tires has a pretty good calculator on there site for figurin out gears.

i got it guys thanks