Idle RPM Question

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Old Jul 26, 2012 | 05:54 AM
  #1  
Benton Quest's Avatar
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Idle RPM Question

Hi All,
I have a 1970 442 with a 455 stock.
Where should the idle RPM's be when in drive stopped at a stop sign? And where should it be with a/c on stopped and in drive?

This car drives great, but at a stop sign etc, it does not cut off, but chops pretty good. That to me seems normal and the idle RPM is around 1000.
BUT, when the a/c is on the idle drops to 500 to 600, the chop is more noticeable. I put the car in neutral to make sure it will not cut off.
Note, the car has never shut off, but feels like it might.
Thanks,
BQ
Old Jul 26, 2012 | 06:19 AM
  #2  
oldcutlass's Avatar
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From: Poteau, Ok
Is it smooth in idle, do you have an idle compensation solenoid for when the A/C is on? Can you define the term "chop", do you mean it runs rough or lopey?
In drive with the A/C on it should be around 600 rpm.
Old Jul 26, 2012 | 06:40 AM
  #3  
MDchanic's Avatar
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From: The Hudson Valley
The A/C on a pre-1973 stock 455 should not cause a noticeable change in idle speed.

Even on a 350, it should be minimal.

There are about a thousand things that could cause this including incorrect carb adjustments, incorrect timing adjustments, incorrect carb, incorrect distributor components, bad points, condenser, plugs, or wires, vacuum leaks, etc., etc., so I won;t speculate about that now.

- Eric
Old Jul 26, 2012 | 06:38 PM
  #4  
Benton Quest's Avatar
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No Dr. but play 1 on TV
 
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Well, I'm at a disadvantage due to my experience of never owning a car like this.
In drive while stopped it has a great sound and it feels like the cam is gently shaking the car. Not bad, just a gently movement. Here the idle is at 800 to 1000.
The same scenario with the a/c going, it drops to 600 or so. The car shakes the same, but a little harder.
I have just got the car and took it out on the Interstate. I got it cruising up to 65. It drove great and very little noise. I did notice the rpm's were at 4000 at 65. I do not know what rear end it has. I hope the 4000/65 is a normal rpm for a highway car.
BQ
Old Jul 26, 2012 | 06:51 PM
  #5  
MDchanic's Avatar
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From: The Hudson Valley
Originally Posted by Benton Quest
I hope the 4000/65 is a normal rpm for a highway car.
For a highway car, more like 1,800 at 65mph. I believe some tall-geared Turnpike Cruiser models turned as little as 1,600.

You've got a fairly low-geared rear there.

- Eric
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