Are What RPMS should a /6 be at while driving 55?

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myasylum

myasylum

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Since I found my car, I never drove it on the freeway. Matter of fact it didn't run at all when I found it sitting in the weeds in back of a bar.
It isn't the stock /6, I assume not the tranny either. It's a 80's motor I believe!??! At any rate I finally drove it on the freeway after I got it running and I swear it 55mph the motor was running at about 4,000RPM's! I have no tack to be sure, but it was running awfully high. I realize it is in part because it's a 3 speed Auto, and these days we are use to overdrive. Since the car was sitting for 2 years I was not real comfortable driving above 55, much less the gas I'm sure it was consuming.
Was this normal for a 73? Is that just how it was back then, or is something screwy? It felt like I was doing 55 in second gear. It sucked, but it was in third.
Any thoughts?
Thanks!
 
Well, being down two cyilnders will create more of a buzz than an 8 will. The RPM is determined by the gear ratio and to a lesser extent, the tire diameter.
You had a tachometer on it and seen 4,000 RPM's?
 
Here is a calculater.

You need to know,
Your what gears you have in the rear.
Your rear tire higth from the ground to the center of the tire.
ie,26' tall tire would be 13'

divide your tire higth by your gear ratio times RPM divided by 168.


Example.

(13) divided by (3.23) times (3000rpm) divided by 168=71.87MPR@3000rpm


You can put in any RPM you want to see what MPH you are runing at that RPM. The 168 is a constint for a 1 to 1 ratio and must stay the same

Hope that helps.
 
Well I don't know why it put happy faces on there and it wont let me edit them out. But the constint is 168.
 
hey burntorange. the reason for the smilies in place of the # 8 is because you are using the combination of the bracket and the # 8.
if you post the "cool" smilie you will see the #8 and the bracket ")" appear.
do away with the bracket thing and it will edit nicely for you.

I know what you meant anyway!!:-D

regards,Rod:)
 
walpolla said:
hey burntorange. the reason for the smilies in place of the # 8 is because you are using the combination of the bracket and the # 8.
if you post the "cool" smilie you will see the #8 and the bracket ")" appear.
do away with the bracket thing and it will edit nicely for you.

I know what you meant anyway!!:-D

regards,Rod:)
Click to expand...


I see said the blind man to his deff son. Thank you.

I was puting in old school smilies and did not even know it. LOL
 
Rumblefish is right. Rolling diameter/circumference of the tire and gear ratio will determine how fast the engine must run at a predetermined speed. A 205/70-14 tire on a 2.76:1 rear gear (typical stock ratio for a 73 auto) would require 2200 rpm to achieve 60 mph assuming no slippage anywhere. This does not account for drag either.
 
I thought the 318 in my Duster was spinning awfully fast at 75 MPH but when I hooked up a tach it was only spinning around 2600 RPM, and that's with a 2.76:1 rear end. Funny too, my redline was around 3500 RPM (hopefully a rebuild/hot-rod tricks will cure that).
 
Burntorange70 said:
Here is a calculater.

You need to know,
Your what gears you have in the rear.
Your rear tire higth from the ground to the center of the tire.
ie,26' tall tire would be 13'

divide your tire higth by your gear ratio times RPM divided by 168.


Example.

(13) divided by (3.23) times (3000rpm) divided by 168=71.87MPR@3000rpm


You can put in any RPM you want to see what MPH you are runing at that RPM. The 168 is a constint for a 1 to 1 ratio and must stay the same

Hope that helps.
Click to expand...
this is easier:
http://vexer.com/68rt/speed.html
 
Slants have a sound all there own... At 3 grand they sound like they may fall apart! They don't but it sounds like it! I have 3.23's and it runs at 70 at 3000 not bad by my standards. I have no standards so don't hold me to that...

TF
 
i've had /6 for ever an a day ran them hard too . i . ive use an abused .ck the oil one day cause the oil pressure was bouncing off 0 took 6 qts to fill it back up oil pressure came back to 40 psi ( had been doing that about a week) i drove over a 100 miles aday back an forth to work in my 82 dodge pick up i had over 500,000 miles on it before i retired ol yeller . it was a 100 still is, its setting out back resting . went to the scrap yard one time had over 2200 lbs of copper wire in it .had to put wood blocks between the springs an body cause the springs were bending backwards . last week end the boy ask if it wood still run ,sat for 2yrs pour a little gas in the carb hook a batt to fired about the third revolution /6 are as tough as they get in my opinion . never blew one up . wore them out first, when i retired ol yeller 65mph was top speed flat on the floor .empty
 
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