Rpm, power band and gear ratios

[Anonymous]

Hello everyone!

I'm in the process of completing a 63 Econoline van.. yes I know I know but its MY little red sports car. I have 250 in it, runs like a top. But, but My concern is this. I have a 3.55 rear gear ratio C4 tranny and 24.25 inch tires. givin me a final RPM of 2999 @ 60MPH

I do belive this to be a bit high?? So the Q is this;
Where the devil is the power band on one of these engines? I am not pulling anything and it is a mainly in town driver, with a few road trips thrown in... Long ones.

I know a 63 Econo aint no caddy and certainly not a road huggin lamborghini so cruising at 70mph is not very likey... just would like to find a rpm where it will run all day and not over spin the motor...

The 3;55's give it lots off the line... for me... I Am not looking to hot rod it... stock is plenty fine by me so I'm thinkin 3;27? 3;08's or jsut bigger tires??? Bigger tires would certainly be the easiest but?? thoughts?

Any thoughts would be greatly appreciated.

Rpm with my stock tires & 3:55's
@ 60 mph 2999
3:27's @ 60 mph 2763
3:08's @ 60 mph 2602

3:55's with 26 inch tires @ 60mph 2732

thanks
Kevin
thunder bay ont.

 

[rbohm]

8) the best fuel economy is going to come when the engine is running at or near its peak torque(on the low side). if peak torque is at say 2500 rpm, then a steady state cruise at 2200-2500 is where you will get best fuel economy. that said, i would keep the 3.55 gears and go with the 26" tall tires.

 

[CZLN6]

Howdy Kevin:

You didn't say what trans you're using? If it is a C4, I'd go with a 3:1 ratio given your driving needs. Between the extra torque of a 250 and the torque multiplying function of the auto torque converter you'll get around town fine, with alot less stress and noise on the highway.

If the rig has a manual trans, I'd go with a 3.25:1, just to save wear and tear on the clutch. If I were going to hit the highway, I'd have a set of tall tires ready for the rear too.

That's my two cents, for what it's worth.

Adios, David

 

[Lazy JW]

... I have a 3.55 rear gear ratio C4 tranny and 24.25 inch tires....

.....it is a mainly in town driver, with a few road trips thrown in... Long ones......

Cheapest and easiest would be to keep what you have for daily use and buy a spare set of taller tires and wheels all mounted up to swap on for those occasional long freeway blasts. Don't forget to compensate for speedometer error.

Truth is, you would never see the payback on a gear ratio swap in your circumstances.
Joe

 

[james singleton]

Kevin, Your post is very interesting to me, since I have a 63' Econo Van. The difference between your set-up and my set-up, is that I have a 200cid engine with a 3-speed manual trans., a 3.50 ratio axle, and with a tire size about the same as your's (24.5"). These "old" vans are definitely not the best "freeway flyers" with their stock configurations, that is for sure! My orginal/stock rear-end was a 4.11 and it felt like the motor was wound tight at around 50-55mph. I installed the 3.50 some years ago and that helped. Since taller wheels seem to be the popular trend these days anyway, I have thought about taller tires; and the fact that I recently installed disc brakes on the front. I wondered about what options would be better for better highway driving??? Changing tire size or a different rear end-ratio?? Do you have any idea what the tallest tire that would work on our "old" econolines??? This might be a good question (what is the tallest tire size that would fit our old vans) for one of the Econoline website. Jim

 

[StrangeRanger]

Some problems with taller tires:

1) You raise the center of mass.

2) If you don't increase wheel diameter as well you end up with taller sidewalls meaning more sidewall flex

Given that the Econoline corners like the proverbial pregnant hippo you may not want to do anything to worsen the handling.

3) Raising the vehicle further off the ground will increase the airflow under it increasing the aero drag and worsening fuel economy.