Timing mark jumps all over the place - Team Camaro Tech
Troubleshooting Diagnosing problems done here.

 
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post #1 of 13 (permalink) Old Apr 24th, 01, 07:20 PM Thread Starter
 
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I have a stock 327 /210 - only modification is a 4 barrel intake / 4 barrel quadrajet from a 350.

I have checked for vacuum leaks - found none.

Distributer is original - timing is set to 14 -

problem is - with the light on it - the timing mark jumps around (as far as 4 degrees) downward.

dwell sets up perfect at 32

plugs are new - wires new - dist cap new - all wires tight

what's my problem?

PS - I'm a beginner - just learning - the above is all I could think of.... let me know if there is something else I need to share with everyone to get the right answer.

Matt
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post #2 of 13 (permalink) Old Apr 24th, 01, 07:33 PM
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Advance spring could be getting weak, the weights could be sticking. The mechanical advance in itself isn't something that we think about in terms of maintaince like we do points and rotors...

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post #3 of 13 (permalink) Old Apr 24th, 01, 09:37 PM
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I have seen this many times on a worn motor. Most likely your timing chain is streched. Pull your coil wire, then with your hands try to move your crank pulley right to left. This will tell you how much slack you have.

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post #4 of 13 (permalink) Old Apr 25th, 01, 06:50 AM
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I was suggest starting with the "advance" mechanisms also. New vacuum advance units are usually available and easy to install if your dist has one. I believe vacuum controls the advance at idle and then the mechanical takes over with higher rpm but I may be off base. The suggestion of checking the timing belt is a good one also. Lastly, make sure that the plate that the points mount to is not binding in any way. This could cause your problem too.
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post #5 of 13 (permalink) Old Apr 25th, 01, 09:10 AM Thread Starter
 
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Question

Have never played with the insides of a distributer before (other than points/condensor/ tune up stuff)

How freely should weights move? does the center plate that the weights connect to move? Do I clean the bottom of the weights up & grease or leave dry? how freely should plate the points are on move? Is there a way to tell if it is binding?

How do I tell if I need to replace the "guts" vs replace the whole distributer?

Matt

PS - Thanks for helping & being patient with a rookie (wannabe) mechanic

[This message has been edited by zippy67 (edited 04-25-2001).]
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post #6 of 13 (permalink) Old Apr 25th, 01, 09:20 AM
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Timing gear and chain the thing is wipping. retarding and advancing the cam making the timing jump around. If it is origonal I guarantee the plastic gear is bad. Don't let it go if it completely breaks it can cause internal damage to the motor.

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post #7 of 13 (permalink) Old Apr 25th, 01, 10:38 AM
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oger and the others bring up a good point about the timing chain... If it has survived 30+ years without being replaced by all means replace it just for the fact that it's lived that long... If the engine has been rebuilt in the last few years or had a new cam installed recently the odds are good the timing chain and gears were replaced and I would start with the distributor...

Remove the cap and rotor and look for worn weights and bushings. You might see grooves where the moving parts have made contact over the years... If you are unsure of how everything should be, I suggest you find a tune up shop that has a dist machine and a tech that knows how to work it.. One hr of labor could be well worth a weekend of frustration....

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post #8 of 13 (permalink) Old Apr 25th, 01, 02:29 PM
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Look at the basics first - when timing jumps around at idle, it's not necessarily the centrifugal advance mechanism, as it doesn't come into play until well over idle rpm; however, could be a vacuum leak between the carb and the vacuum advance can or a leaky can. Disconnect the vacuum advance (plugging the hose) and see if timing still moves around - if not, you found the problem; if it still moves around, chances are it's worn distributor shaft bushings and/or excess vertical play between the distributor gear and the bottom of the housing. I'd bet on the latter - see it all the time on 30-year-old cars.

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post #9 of 13 (permalink) Old Apr 25th, 01, 05:03 PM
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If the dwell stays put I don't think the bushings are loose or there is excessive end play in the dist. shaft.

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post #10 of 13 (permalink) Old Apr 25th, 01, 05:58 PM
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i hate pipe up here because you guy's are giveing such good advice, but we all foregot one thing.

if you have a 30+ year old harmonic balancer you can get this. the rubber ring could be dry roted out or just plain shot from use alowing the outer ring to jump around a bit.

i would check the timing chain first, then the vacuum advacne. but i would also check the harmonic balancer. they do not go bad often, but it dose happen. and 30+ year's is a long time to live for a part like this if used alot as a daily driver.

[This message has been edited by ilbl8 (edited 04-25-2001).]
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post #11 of 13 (permalink) Old Apr 26th, 01, 06:36 PM Thread Starter
 
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Thanks for all of the input guys!

I ordered the adjustable vacuum advance unit that Crane makes. Figured I would start with some easy stuff.

It came in today!

I Changed the springs -> boy were the weights nasty -> little rust -> little gunk. Me and my dremel cleaned em up!

Started car, timing was strong 14, mechanical added 24 for a total of 38 (I did that right didn't I? this is without the vacuum advance plugged in, but plugged)at a little over 3200 rpm.

I'm glad it wasn't timing chain, that was more work than I'm ready for. The balancer is 35 years old, so that scared me too.

Thanks for helping me out.

Matt

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post #12 of 13 (permalink) Old Apr 26th, 01, 06:52 PM
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Always glad to here when a problem is resolved!!

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post #13 of 13 (permalink) Old Apr 27th, 01, 05:50 AM
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That's the first time I have heard of rusty weights doing that they usually just lock up. You learn something new every day. Glad it was simple.

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