Highway Revs

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MOPARJ

MOPARJ

What can I upgrade now?
Joined
Nov 3, 2006
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Thousand Oaks, Ca
My Duster with 3.91s runs about 3500-3600 rpm at 68-70 mph. Usually I will run around 3300-3400 rpm on the highway, but sometimes you need to run a little quicker to keep up. Eventually a 4 speed will be going in. Tires are 255/60/15s. Motor is a warmed over stock compression 318 (with XE268 cam) with 45K since the last rebuild. Doesn’t use a drop of 15w40 Delo oil between changes. The engine buzzing doesn’t bother my ears, but with regular oil changes (every 1500 miles), am I flirting with danger at the revs mentioned? I don’t think so, but just wanted to hear some opinions!
 
No real danger. Your engine will run at those RPM's as long as you want to listen to it and/or FEED it.
 
I wouldn't like to run with that high of rpm. Most certainly won't hurt it though.
 
Made it 45k so far.....Just stay off the highway. :)

If you keep up the maintenance like you have, it's more of a annoyance then anything else. I put quite a few miles on 4.10/4.56 gears in the 70's. All I can say is, even though you have a fairly mild cam, the valve springs will generally be the first things to let you know when it's time to look into the engine.
 
Run hell out of it.
 
Better get on the Passon 5 speed waiting list, that would help you in the rev department!
 
No kiddin. These cars were geared like that from the factory and lasted just fine.
 
I hear what the OP is sayin' though. That RPM on the highway for long distances is no fun not to mention what it does to your gas gauge! The teen will be fine but can your wallet survive?

When I have a choice I always take the outer road or smaller highway where the speed limits are lower rather than trying to keep up with the masses at 70 on the interstate.
 
To what some had said about mileage, it is actually about the same as when I had the 3.23 gears. 12-14 average combined. As for the oil, 1500 miles is about 4-5 months time on the oil, so I moved the change interval up.
 
When I worked as the alignment tech for a local tire chain years ago we had a customer who had a truck I REALLY pined for. It was a Chevy. I remember it well.

It was a 73 C30, single rear wheel Camper Special with a 400 small block, NP435 4 speed and a Dana 60 with......wait for it........4.56 gears from the factory. It had like 120K on it at the time. He and his wife had bought the truck new to pull a travel trailer.

They had been to all 49 continental states with that thing. I was lucky enough to test drive it on several occasions and it was a hoot to drive. In fact, STILL know where it is. His son has it now and is doing a complete restoration on it.

I remember him saying that he loved driving it because the response was "right there" when you mashed the gas. It was, too. So, short gears certainly CAN be diven long distances. Course that truck had like a 7.50/16 or some such on it, so it had some height, but still a gear is a gear. lol
 
RustyRatRod said:
No kiddin. These cars were geared like that from the factory and lasted just fine.
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True enough, they also came with bias ply tires and 4 wheel drum brakes but last time i checked it is now 2015 not 1964 and things have changed a bit so why not go with some upgrades to make your ride a bit more user friendly not to mention the price of gas has gone up just a touch since back in the day.
 
gold66cuda said:
True enough, they also came with bias ply tires and 4 wheel drum brakes but last time i checked it is now 2015 not 1964 and things have changed a bit so why not go with some upgrades to make your ride a bit more user friendly not to mention the price of gas has gone up just a touch since back in the day.
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I never recommended against any of that.
 
When I originally changed to a manual tranny, I used the 3 speed with the over drive. Mean 1st gear and the OD was sweet. If I remember right it was about 7 or 800 rpm less than the auto.
 
RustyRatRod said:
When I worked as the alignment tech for a local tire chain years ago we had a customer who had a truck I REALLY pined for. It was a Chevy. I remember it well.

It was a 73 C30, single rear wheel Camper Special with a 400 small block, NP435 4 speed and a Dana 60 with......wait for it........4.56 gears from the factory. It had like 120K on it at the time. He and his wife had bought the truck new to pull a travel trailer.

They had been to all 49 continental states with that thing. I was lucky enough to test drive it on several occasions and it was a hoot to drive. In fact, STILL know where it is. His son has it now and is doing a complete restoration on it.

I remember him saying that he loved driving it because the response was "right there" when you mashed the gas. It was, too. So, short gears certainly CAN be diven long distances. Course that truck had like a 7.50/16 or some such on it, so it had some height, but still a gear is a gear. lol
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That's, a nicely optioned pickup. Double down, on torque.
 
MOPARJ said:
My Duster with 3.91s runs about 3500-3600 rpm at 68-70 mpg. Usually I will run around 3300-3400 rpm on the highway, but sometimes you need to run a little quicker to keep up. Eventually a 4 speed will be going in. Tires are 255/60/15s. Motor is a warmed over stock compression 318 (with XE268 cam) with 45K since the last rebuild. Doesn’t use a drop of 15w40 Delo oil between changes. The engine buzzing doesn’t bother my ears, but with regular oil changes (every 1500 miles), am I flirting with danger at the revs mentioned? I don’t think so, but just wanted to hear some opinions!
Click to expand...
I wouldn't worry, about it....
 
heres my 340, has an a833 of and 3.91 gears. its a nice highway cruiser even with the solid roller. I just can't stand having an engine revving up that high on the freeway, thats why i hate lil 4 bangers.

 
In 1977-1980 I drove my Cuda everywhere with 4:56 gears and a 440 6-pack. Very seldom was I ever on the highway but I remember going to an Oriole game in Baltimore which was about a 60 mile trip south in it and top speed was around 50 mph. Took forever to get there but that thing was over 4000 RPM the whole way. That car was so much fun on the street my first 3 years out of high school. My dad owed a gas station back then and he cut off my credit for gas because I was charging over $100 a week. Some days I would have to fill up the tank twice a day. I drove it like I stole it! But I never hurt that engine from high RPM's! And I dragged raced it almost every weekend during those 3 years.
Rod
 
The older I get, the more I like my comfort. I pulled my 833 for an 833OD. With 3.23 gears at 60MPH, I'm turning 1900 RPM and don't have a headache after a trip.
 
breakstuff said:
The older I get, the more I like my comfort. I pulled my 833 for an 833OD. With 3.23 gears at 60MPH, I'm turning 1900 RPM and don't have a headache after a trip.
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I don't know your engine combo but I guess you get 18-20 mpg.
 
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