No high RPM power - Page 2 -

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post #16 of 20 Old 05-21-2013, 07:53 AM
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1981 CJ7 
Join Date: May 2011
Location: Elbert
Posts: 17,185

I've read there are two distinct difference between the pre and post computer Motorcraft dizzys.

1. The pre-computer head has 13 and 18* advance slots. The computer version has 7 and 8* slots, roughly.
2. The computer version has a smaller range of vac advance that comes in slightly sooner.

I've had decent success with the NAPA re-man'd Motorcraft dizzys. If you decide get one, ask for a 1979 Jeep CJ distributer, and confirm that it has the correct 13-18* head. You can see the advance slot labels thru a little peep hole in the top plate.


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post #17 of 20 Old 05-21-2013, 08:30 AM Thread Starter
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1984 CJ7 
Join Date: Apr 2013
Location: Pilot Mountain
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Thanks Matt,
In that case my distributor is already pre-computer. Saves me some trouble but I would hoping that this was going to be the solution.

I just ordered a tach for under the hood. Once it arrives, I will plot the advance curve and see what is next. Luckily, the Jeep is completely usable as is, so there is no rush. If the advance is late, like I think it is, then I will make either a spring change or a weight change. As stated, it does advance, but I am not sure that it revs high enough on the road to start advancing.
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post #18 of 20 Old 05-24-2013, 05:19 PM Thread Starter
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Join Date: Apr 2013
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My tiny-tach showed up today and it confirmed what I thought. I see no move in the centrifugal advance until ~2100 and I don't seen any real movement until almost 2400.

Springs too strong? It seemed smooth once it started moving and also when I turned the trigger manually, so I don't think its an issue of friction.

Will be away from the Jeep until next sat so any more adjustments will have to wait 'til then.
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post #19 of 20 Old 06-09-2013, 09:12 PM Thread Starter
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Been too busy to make any changes or do any more testing. But I have driven with it with the OEM tach and the new tach side by side. What I have found it that the power doesn't drop at an RPM as low as I thought. The OEM tach reads 500 RPM high at low revs and ~500 RPM low at high revs. So the engine doesn't fall flat at 3K like I thought but at 3500 which seems to be a little more like what I should expect.

I will still seek more centrifugal advance at some point.
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post #20 of 20 Old 06-09-2013, 09:21 PM
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Join Date: Sep 2011
Location: Rochester
Posts: 2,279
This may help;

Tune up on a 285 / Weber Carburetor / Distributor / Timing / Advance / Discussion

The guys helping you know what they are talking about.

Glenn R. Lever
Rochester, New York 14617-2012
My Web Site

My restoration thread here on the Jeep forum
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