Speed/RPM
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Speed/RPM
Speed/RPM
Hi 👋 I’m new here!
I hope my following question is not too trivial:
Short Info: 1966/67 CS 442 400cui -3gear automatic - 120.000 miles - Edelbrock Carb, new headgasket - good compression.
My first American V8! A Dream Come true! But new territory for me:
I‘ve been driving for three hours on the interstate today. It felt like the car was most comfortable at around 55-60mph at ~1.500rpm(if the gauge is right)
My Question is: what maximum speeds or rpm would you guys recommend for this kind of engine (age/ mileage). I don’t want to compete on the left lane, but I’m wondering if I should really rev it up from time to time(of course when engine warm etc) for the engines sake(the official max speed for the car is said to be ~125mph) or if I should just leave it and never go over 80mph?
Thanks a lot !
Moe
Last edited by LomitaToHamburg; Nov 8, 2018 at 12:41 PM.
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Joined: Feb 2013
Posts: 15,409
From: Phoenix, AZ
Here in the states 80 MPH is about as fast as you can legally go on the highway (75 MPH posted speed limit), so most folks would not be cruising above that speed on a regular basis.
At one point my car had short rear tires, which along with the 3.23:1 rear gears put the engine at ~3200 RPM on the highway (~70 MPH). I had no issues with cruising at that engine speed for several hours at a time.
At one point my car had short rear tires, which along with the 3.23:1 rear gears put the engine at ~3200 RPM on the highway (~70 MPH). I had no issues with cruising at that engine speed for several hours at a time.
Last edited by Fun71; Nov 8, 2018 at 01:19 PM.
'87 Delta 88 Royale
Joined: Dec 2010
Posts: 2,514
From: Margate, England
Does the car have a temperature gauge?. I suggest you keep an eye on it for any prolonged driving at the speed limit. BTW last time I was there a good part of I10 in west Texas had an 80mph limit.
It's far from unknown for older cars to have a partially plugged radiator, you do't need to find yours has after the engine has been cooked.
Having said that if the drivetrain is in good shape and your tires are good then the engine won't be at all strained at highway speeds.
Roger.
It's far from unknown for older cars to have a partially plugged radiator, you do't need to find yours has after the engine has been cooked.
Having said that if the drivetrain is in good shape and your tires are good then the engine won't be at all strained at highway speeds.
Roger.
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Joined: Apr 2015
Posts: 140
From: Langenfeld, GER
Recognizing your license plate you seem to be in Germany.
There was a similar question from another member who wanted to go (for a longer time) as fast as possible on the Autobahn, maybe this helps:
https://classicoldsmobile.com/forums...light=autobahn
If I am with my Cutlass on the Autobahn I always cruise on the right lane with ~120km/h @ approx. 2.700rpm. Relaxing. And if you have to overtake fast a truck there is enough power left, going a few seconds with higher rpm won´t damage anything unless everything is already in a very bad condition.
There was a similar question from another member who wanted to go (for a longer time) as fast as possible on the Autobahn, maybe this helps:
https://classicoldsmobile.com/forums...light=autobahn
If I am with my Cutlass on the Autobahn I always cruise on the right lane with ~120km/h @ approx. 2.700rpm. Relaxing. And if you have to overtake fast a truck there is enough power left, going a few seconds with higher rpm won´t damage anything unless everything is already in a very bad condition.
Last edited by Levellord; Nov 8, 2018 at 11:40 PM.
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So, I‘m gonna post the next question how to measure/ fix the rev counter(rally pack) in a new thread?
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Fun71, rustyroger and levellord; thank you for your answers/ ideas so far!!
Yes, with Interstate I meant Autobahn - I just wasn’t sure how many would be able to relate and also thought there weren’t any Germans here
But I really love the original setup and want to keep it that way(although interesting info about the overdrive trans). The Car just drives and feels ridiculously beautiful on lower speeds (40-50) so at the moment I wouldn’t want to change that.
Greetings
Moe
Yes, with Interstate I meant Autobahn - I just wasn’t sure how many would be able to relate and also thought there weren’t any Germans here
But I really love the original setup and want to keep it that way(although interesting info about the overdrive trans). The Car just drives and feels ridiculously beautiful on lower speeds (40-50) so at the moment I wouldn’t want to change that.
Greetings
Moe
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Joined: Aug 2013
Posts: 12,796
From: Evansville, IN
You don't want to beat down the road for an hour at 120 mph, but the car should be able to do 100 mph easily for a few minutes at a time. Brakes and suspension must be in correct working order. The standard gear for that car in the differential is 3.08 to 1, which results in @2800 rpm at 70mph. The car should have no issues at all at that speed forever, and should have no issues other than maybe a little heat at 80 mph for extended times. 90 and watch your gauges is ok too.
The factory ralley pac is fun, but aren't very accurate. You may need additional gauges. As long as you have oil pressure and are not overheating, you are ok.
The factory ralley pac is fun, but aren't very accurate. You may need additional gauges. As long as you have oil pressure and are not overheating, you are ok.
Thread Starter
Registered User
Joined: Nov 2018
Posts: 43
You don't want to beat down the road for an hour at 120 mph, but the car should be able to do 100 mph easily for a few minutes at a time. Brakes and suspension must be in correct working order. The standard gear for that car in the differential is 3.08 to 1, which results in @2800 rpm at 70mph. The car should have no issues at all at that speed forever, and should have no issues other than maybe a little heat at 80 mph for extended times. 90 and watch your gauges is ok too.
The factory ralley pac is fun, but aren't very accurate. You may need additional gauges. As long as you have oil pressure and are not overheating, you are ok.
The factory ralley pac is fun, but aren't very accurate. You may need additional gauges. As long as you have oil pressure and are not overheating, you are ok.
Thread Starter
Registered User
Joined: Nov 2018
Posts: 43
You don't want to beat down the road for an hour at 120 mph, but the car should be able to do 100 mph easily for a few minutes at a time. Brakes and suspension must be in correct working order. The standard gear for that car in the differential is 3.08 to 1, which results in @2800 rpm at 70mph. The car should have no issues at all at that speed forever, and should have no issues other than maybe a little heat at 80 mph for extended times. 90 and watch your gauges is ok too.
The factory ralley pac is fun, but aren't very accurate. You may need additional gauges. As long as you have oil pressure and are not overheating, you are ok.
The factory ralley pac is fun, but aren't very accurate. You may need additional gauges. As long as you have oil pressure and are not overheating, you are ok.
'87 Delta 88 Royale
Joined: Dec 2010
Posts: 2,514
From: Margate, England
You don't want to beat down the road for an hour at 120 mph, but the car should be able to do 100 mph easily for a few minutes at a time. Brakes and suspension must be in correct working order. The standard gear for that car in the differential is 3.08 to 1, which results in @2800 rpm at 70mph.
Roger.
Registered User
Joined: Jan 2010
Posts: 6,104
From: central Indiana
I would think if you geared the car to put the engine speed at its sweet spot (at whatever vehicle speed you want) as long as the tires, suspension, and cooling system is good for the speed you could cruise at 100plus all day.
Olds offered a 3.91 axle ratio from the factory, no way they would have done that if it would have resulted in warranty issues. If you wanted a gear that steep, other options were required (heavy duty cooling for example). Take a car equipped with 3.91 on the interstate, the engine is going to be spinning pretty fast. Now swap in a 2.56 gear, the car is going to be going much faster at the same engine speed. All things being equal, no harder on the engine than the 3.91. Assuming the engine has the torque to push the car at those speeds the engine doesn’t care what rear ratio you have.
The other option would would be a overdrive trans. Gear the rearend to put the engine in it’s sweet spot at the desired cruising speed with the converter locked and in overdrive. A trans cooler would be a good idea.
Olds offered a 3.91 axle ratio from the factory, no way they would have done that if it would have resulted in warranty issues. If you wanted a gear that steep, other options were required (heavy duty cooling for example). Take a car equipped with 3.91 on the interstate, the engine is going to be spinning pretty fast. Now swap in a 2.56 gear, the car is going to be going much faster at the same engine speed. All things being equal, no harder on the engine than the 3.91. Assuming the engine has the torque to push the car at those speeds the engine doesn’t care what rear ratio you have.
The other option would would be a overdrive trans. Gear the rearend to put the engine in it’s sweet spot at the desired cruising speed with the converter locked and in overdrive. A trans cooler would be a good idea.
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