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post #1 of (permalink) Old 03-01-2002, 12:48 PM Thread Starter
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Distributor Recurve

How do I recurve my stock distributor on my 86 CJ7 258? Can I just buy a kit? If so what kit should I buy? If not where should I take it to get the work done?

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post #2 of (permalink) Old 03-01-2002, 03:26 PM
 
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Re: Distributor Recurve

You can recurve your self, but it's VERY difficult if you don't know exactly what you are doing.

You have several factors you have to take into consideration, and you will need a distributor machine to do the job correctly.
You will have to consider everything from atmospheric pressure, and ambient air temp. to engine vacuum range and vehicle weight...

What EXACTLY do you want from your vehicle that you are not getting now?
More top end power,? More 'Zip' on takeoff?, Better fuel milage?, better load towing ability?, Ect...

So many cats, so few recipes...
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post #3 of (permalink) Old 03-01-2002, 07:54 PM
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Re: Distributor Recurve

Is it recommended to change the mechanical advance springs to the ones that were posted when the upgrade was first posted a couple years ago? I don't recall the numbers off hand though.

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post #4 of (permalink) Old 03-01-2002, 11:30 PM Thread Starter
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Re: Distributor Recurve

I am not sure I understand the reason for or what recurving a ditributor means. I have an 86 CJ7 258 that has allot of miles on it and a stock distributor. I am getting my engine rebuilt and want to make sure that everything is just right when I put it back together. I was under the impression that recurving the distributor was a way to put it back into new condition. If that is right, that is what I want to do. If not what does it do? What needs to be done to do what I want?

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post #5 of (permalink) Old 03-02-2002, 06:54 AM
 
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Re: Distributor Recurve

Mike-
To my knowledge, re-curving the distributor is not a rebuild. The purpose of re-curving is changing the advance characteristics. (how quickly the advance comes in, and under what conditions) That's why TR was asking you what exactly you wanted it to do that it wasn't doing. As far as reliability, there's not much to wear out in one. You wouldn't need to "rebuild" it normally for a new engine.
I hope that made sense... :-)

BillR
'86 CJ-7, 360, T-18, Dana 300, OEM Dana 44, locked and loaded!
'97 TJ, bone-stock (for now...)
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post #6 of (permalink) Old 03-02-2002, 10:33 AM
 
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The Meat Ball Answer....

* WILL Asked,*
* Is it recommended to change the mechanical advance springs to the ones that were posted when the upgrade was first posted a couple years ago?
I don't recall the numbers off hand though.*

Mr. Gasket P/N 925D if I remember correctly. (about $5 from http://summitracing.com
Jeep used some VERY stiff springs on one side (Centrifugal Advance uses Total Spring Pressure, so you can play mix and match) and a medium spring on the other.
If you switch to two mediums, you will get a little more 'Zip' in the power curve of the engine.
<hr>
*86CJ7 Asked,*
*I am not sure I understand the reason for or what recurving a ditributor means.
I have an 86 CJ7 258 that has allot of miles on it and a stock distributor.
I am getting my engine rebuilt and want to make sure that everything is just right when I put it back together.
I was under the impression that recurving the distributor was a way to put it back into new condition.
If that is right, that is what I want to do.
If not what does it do?
What needs to be done to do what I want?*

I think you have confused Re-Manufacture with Re-Curve.

Re-Manufacture or Re-Build, is to put the distributor back into Like New (Or Better!) condition.

Re-Curve is to change the distributor's advance mechanisms to change the amount of advance the distributor will produce at any given vacuum, load, or RPM.
When you Re-Curve you are fundamentally changing the factory pre-set advance to optimize the timing for your application.
<hr>
*BillR Wrote,*
* Mike-
To my knowledge, re-curving the distributor is not a rebuild.
The purpose of re-curving is changing the advance characteristics.
(how quickly the advance comes in, and under what conditions)
That's why TR was asking you what exactly you wanted it to do that it wasn't doing.
As far as reliability, there's not much to wear out in one.
You wouldn't need to "rebuild" it normally for a new engine.
I hope that made sense... :-)*

Bill Is correct on most counts here.
The only thing I take exception with is the amount of wear a distributor gets...

Just because the distributor still gets the engine started and gets it to the grocery store and back doesn't mean it didn't wear out a long time ago.
Most distributors could use a rebuild around 50K miles, and 'Factory' or 'Remanufactured' tolerances will never do for making power.
(This is FREE horsepower, torque and fuel milage! You already have the ignition, all you are doing is 'Tightening Up' the factory tolerances! It costs virtually nothing! $0.50 for shims and roll pins in most cases.)

If the thrust shim gets worn, the shaft can rise up and make the rotor collide with the cap towers, or break off the center electrode in the cap.
(The rotor can 'Shudder, Wobble, or Bob Up & Down")

When the drive gear gets worn, it allows a lot of 'Slop' in the timing, and correct spark timing is CRITICAL to making ANY amount of real horsepower, torque or fuel economy.
The 'Slop' is also VERY hard on the oil pump shaft and oil pump.

Rotor Phasing is also a VERY BIG consideration.
The Rotor will advance and retard (moving) in relationship to the terminal location on the distributor cap (fixed).
If the Rotor starts out already even or slightly advanced of the terminal, and you add more advance, the rotor will be closer to the next terminal, and in many cases, fire that next terminal! (90 degrees too soon!)
<hr>
*86CJ7 Asked*
*Yes, that was exactly what I was starting to think.
I am getting a RV type (high torque) camshaft installed in the new engine.
The jeep is mostly for off road, hunting, and in town driving, so I want lots of bottom end power.
Is it worth while having the distributer recurved for this purpose? *

I would think so... (but this stuff comes naturally to me, so it seems very easy...)
Once the new engine is broken in, I'd try a little bit at a time with the distributor.

I'd try some new springs, and maybe use the larger advance slot while I had the springs out.
You WILL have to still look and listen for signs of detonation and correct fuel metering while you are doing this, but for breaking in the engine, I'd stick with a stock distributor, with the cap, rotor, coil and plug wire upgrade.
<hr>
Rotor Phasing,
Most stock distributors will be in the general ball park of correct in respect to the Rotor Phasing. (usually not more than 13 to 18 degrees off)

If you have taken the gear off, or bought a remanufactured distributor, the chances are 50/50 the rotor phasing is off somewhere between 13 and 45 degrees, (that's 26 and 90 Camshaft degrees!)

This is just another aspect that I cover when I 'Tune' a distributor or 'ReCurve' a distributor....
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post #7 of (permalink) Old 03-02-2002, 11:05 AM Thread Starter
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Re: Distributor Recurve

Yes, that was exactly what I was starting to think. I am getting a RV type (high torque) camshaft installed in the new engine. The jeep is mostly for off road, hunting, and in town driving, so I want lots of bottom end power. Is it worth while having the distributer recurved for this purpose?

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post #8 of (permalink) Old 03-02-2002, 11:17 AM
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Re: Distributor Recurve

Just do the TR upgrade or an HEI conversion, don't bother to mess with the stock ignition, there's not much improvement you can make with it.

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post #9 of (permalink) Old 03-02-2002, 01:05 PM
 
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Re: Distributor Recurve

If you wanted to play with different characteristics, you could throw an MSD distributor in there. They use the GM sytle spring/centrifugal advance which affects your curve, but I think they are more than a little pricey. I vaguely remember somebody having a cheapie fix for doing that with a stock distributor, but don't remember the specifics. When I put the MSD in mine, I needed a new distrib anyways, so I just bit the bullet.

'83 CJ-7 nothing original but the tub and axle tubes
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post #10 of (permalink) Old 03-02-2002, 04:59 PM
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Re: Distributor Recurve

between 13 and 45 degrees, (that's 26 and 90 Camshaft degrees!)

Wouldn't 13 and 45 crankshaft degrees be 6.5 and 22.5 camshaft degrees respectively?

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