centrifugal advance - JeepForum.com

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post #1 of 20 Old 09-12-2011, 02:46 PM Thread Starter
csrcn2
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centrifugal advance

So I've determined the reason my 89 yj 258 tends to bog down under throttle...not enough advance from the distributor. Still a stock dizzy, gonna replace with a reman for a pre smog vehicle. The dizzy itself I can find at a local parts store but the cap, rotors and adapter must be ordered. Does anyone know if my stock cap work with the reman. dizzy until the new parts arrive?

It is already nuttered with an MC 2150

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post #2 of 20 Old 09-12-2011, 02:50 PM
dancytron
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Don't replace it with the stock cap. Replace it with better Ford parts.

http://www.jeepforum.com/forum/f8/i-...nitive-669495/

The stock parts will work though.
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post #3 of 20 Old 09-12-2011, 03:53 PM Thread Starter
csrcn2
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Yea, like I said just temporarily until I can get the other parts
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post #4 of 20 Old 09-12-2011, 05:12 PM Thread Starter
csrcn2
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Anyone else experience this problem? Just curious to see if this is a common problem with this carburetor mod.
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post #5 of 20 Old 09-12-2011, 08:36 PM
4.7stroker
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You can reuse what you have on your old dizzy.
Yes I found that a pre smog dizzy made a lot of difference.
I am shocked that none of your local parts houses have the cap/adaptor/rotor on hand.

Dwayne
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post #6 of 20 Old 09-12-2011, 09:28 PM Thread Starter
csrcn2
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Quote:
Originally Posted by 4.7stroker
You can reuse what you have on your old dizzy.
Yes I found that a pre smog dizzy made a lot of difference.
I am shocked that none of your local parts houses have the cap/adaptor/rotor on hand.

Dwayne
No one has it. I thought the same thing. 2 to 3 days shipping. Checked auto zone, advance auto, napa, pep boys. Not the right time to buy parts for an old Ford truck
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post #7 of 20 Old 09-13-2011, 05:27 AM
wanabejeeper
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Anyone have the part number for this distrib?

87 YJ The Original!

Quote:
Originally Posted by Anticanman View Post
It goes in that barrel you wheel out to the street once a week.

My build thread http://www.jeepforum.com/forum/f12/n...thread-867043/
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post #8 of 20 Old 09-13-2011, 01:43 PM Thread Starter
csrcn2
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Quote:
Originally Posted by wanabejeeper View Post
Anyone have the part number for this distrib?
Part No. 30-4691 at advance auto, same for auto zone
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post #9 of 20 Old 09-13-2011, 01:45 PM Thread Starter
csrcn2
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SO, after installing the new dizzy, she runs better but still has a case of the hiccups here and there. Tuned accel pump to every setting possible, gives a big shot of smoke during deceleration. Any ideas?
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post #10 of 20 Old 09-13-2011, 04:47 PM
4.7stroker
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Is your vac source for the vac advance ported or manifold? I prefer manifold, this will involve a little retune on the idle mixture screws and resetting the curb idle.
Did you set your idle mixture screws with a vac gauge or by ear? What is your timing set at?

Dwayne
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post #11 of 20 Old 09-13-2011, 05:38 PM Thread Starter
csrcn2
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Quote:
Originally Posted by 4.7stroker View Post
Is your vac source for the vac advance ported or manifold? I prefer manifold, this will involve a little retune on the idle mixture screws and resetting the curb idle.
Did you set your idle mixture screws with a vac gauge or by ear? What is your timing set at?

Dwayne
Idle mix set with a vac gauge, i've set initial timing @ 8*BTDC, have tried advancing a few more degrees and retarding a few and no change. I have an inline fuel filter installed before the stock one so i know i'm getting fuel. The return fuel line is still in use also. Spent plenty of time checking for vac leaks, none found and it holds steady vacuum at about 21".
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post #12 of 20 Old 09-13-2011, 07:49 PM
Old4X
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How many degrees of slack in your timing chain? What is the CFM flow rate on your air filter? Have you tried tuning the vacuum advance module (use an 1/8 inch allen wrench through the vac nipple).

418 miles on 19 gallons of gas. Can't beat the BBD !
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post #13 of 20 Old 09-13-2011, 09:14 PM Thread Starter
csrcn2
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Quote:
Originally Posted by Old4X
How many degrees of slack in your timing chain? What is the CFM flow rate on your air filter? Have you tried tuning the vacuum advance module (use an 1/8 inch allen wrench through the vac nipple).
I'll give that a shot tomorrow. Thanks
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post #14 of 20 Old 09-14-2011, 05:23 AM
Karma
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HI,
I'm confused. When you say bogging down what exactly do you mean? I suspect you don't understand how the advance system works.

At idle, the advance is a certain value. This is determined by the initial advance value plus the applied vacuum. As RPM is slowly increased, the advance will increase due to centrifugal advance up to some certain maximum value. However, if, at a certain steady RPM, say 2000, and you then stab the gas, the vacuum advance RETARDS the timing to prevent pinging. Then as the situation stabilizes the advance returns to whatever value is appropriate for the engine RPM. This will NOT be the same as the Idle value.

I don't see your problem as being helped by increasing the advance. You should use a timing light and adjust initial advance with the distributor without the vacuum connected. Be sure to plug the vacuum line. Then attach the vacuum line to the distributor. Then stab the gas and you should see the timing retard momentarily then advance to a new value. If you increase the gas slowly, you see the timing advance with RPM as determined mostly by the centrifugal advance weights.

Sparky
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post #15 of 20 Old 09-14-2011, 06:45 AM Thread Starter
csrcn2
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I agree, I think its possibly to much advance for the large size tires im running. The engine can't handle the load. I'll make the appropriate adjustments and get back to ya
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