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Topic Review (Newest First)
04-29-2010 12:20 PM
74chevyflat LMAO!!!! wow didnt notice how old it was. hahahaha
04-29-2010 08:37 AM
Regal Beagle This thread opens up the age old argument of ported vs. manifold vacuum debate.
I believe this piece is written by a GM engineer.

04-28-2010 10:06 PM
ericnova72 Being as it was 8 years ago I hope he got it fixed by now.
04-28-2010 09:28 PM
T-bucket23 Have you put a timing light on it to see what the initial timing is with the vacuum advanced disconnected. You need to know where you are to start with before looking at advance issues.
You should be at about 12btdc to start with
04-28-2010 06:45 PM
74chevyflat u may even be off a tooth. i had the same problem with my six cylinder in my chevy pickup when i first rebuilt it. be fore the rebuild i had all the lifters frozen. changed everything ou. and it ran like a top for about 30 seconds. and then it ran like poo from then on i tried everything. it may hae been a blown bridge on the head gasket too
08-16-2002 05:41 AM
66chevy2ss Jeez, here I go again! Thanks for your patience.

Could it be that (in my ignorance) I applied so much pressure on that hand pump that the vacuum advance mechanism went to its fullest potential, and then clicked back to its starting place? (therefore accounting for the "click" noise)?

If this was the case, perhaps this part isn't faulty.
08-16-2002 04:23 AM
66chevy2ss Thanks for the excellent replies. I guess I'll go and bite the bullet!
08-15-2002 11:11 PM
mmetalman my 2 cents worth:
The distributor shaft should turn, but not move sideways. I just repaired my 69 Cougar's dist with this prob since with points any sideway play will throw the point's gap out to lunch. It also affects later non-point dists as timing advance may have to comensate for the play. If it's really bad the star can actually hit the pickup coil causing irradic or non-funtioning spark.
08-15-2002 06:38 PM
4 Jaw Chuck Whoa, let me explain a little better.

The shaft is what rotates in the distributor and is how the rotor can deliver spark to each plug wire attached to the cap.

This shaft is driven by a gear off the camshaft and turns half crankshaft speed. The point/pickup are below the rotor and are the mechanism that lets voltage flow to the coil and also interrupts it (spark!).

The coil is a short term storage device that also happens to step up the voltage of the power coming from your battery, when power is flowing to the coil there is no spark-you need the rotor to be aligned for the power to have a place to go.

When the rotor is correctly aligned power will flow through the coil to the rotor conductor only when the pickup or breaker opens-interrupting current (power) flow to the coil. You can think of it as a dump truck filling (coil) and when the time is right the pickup/breaker trips the dump mechanism and the power will pour through the rotor to the cap-to your plugs wires and ultimately to your plug.

As you can see timing is everything and if there are any worn components such as a shaft that has freeplay it will change the time when the dump occurs, usually not in the same way each time. When this happens it is called spark scatter and means each cylinder will have a differently timed spark event with each revolution. This is not good.

Distributor shafts should have zero play in their bearings but the reality is most factory style distributors run in plain bearings (aluminum bore). As you can imagine these aluminum bores wear and when they do they develop clearance between the shaft and the bore (freeplay). Any freeplay will cause scatter to a certain degree. Worn advance components will also move the timing around by not being smooth in their movement or just binding and not advancing at all.

That click you hear is likely the mechanical advance or vacuum advance mechanism not moving smoothly, obviously it's worn. The red powder is another indicator.

Although their may be other factors contributing to your problem you cannot rule out the timing because you know the distributor is worn and is not functioning it's best. This is important enough that when I rebuild a motor there are a few things I replace right off the hop;

Distributor, fuel pump, water pump, oil pump and drive shaft, pushrods, rockers, lifters. These are all as important as each other and all are high wear/high stress components that are critical to the life of the engine in some way.

So what I am saying is you have found one problem, fix it. If is the only problem we can give high fives and go and race. If not then we look for the next problem and solve that one too, beer can wait. You can't solve your problem without fixing a possible contributor when you know it is bad. Hopefully it is the only one but likely it's not.

What this is called is HotRodding 101 and the lesson is "if it's broke, fix it!" The payback is certainly worth it. Let us know how it works out, diagnosing problems over the internet is hard enough without knowing if you ever got the problem solved. See you soon.
08-15-2002 05:16 PM
66chevy2ss Something was moving in there, I'm not sure if it was the shaft.

At any rate, it made a suspicious "click" sound, twice, as if it was sticking. I have no idea...

Thanks for the help.
08-15-2002 04:13 AM
66chevy2ss But isn't the shaft supposed to move?
08-14-2002 08:41 PM
4 Jaw Chuck Sounds like time for a new distributor. Especially since you told me the shaft moves.
08-14-2002 05:29 PM
66chevy2ss By the way, the reason I'm so interested in this is that the guy I bought the car from suggested that there was something wrong with the vacuum advance.
08-14-2002 05:28 PM
66chevy2ss Lloyd Topping and 4 Jaw:

I stuck a vacuum pump on the hose leading to the distributor, and was able to pull a vacuum. It held the vacuum as well.

The vacuum advance linkages did move, though I couldn't see exactly what they did (I didn't take the distributor and roter completely off, I just lifted the cap up).

But the linkages sort of "clicked", twice, as I was pumping vacuum (as if they held, and then moved quickly). Could it be that the mechanism is sticky?
08-13-2002 08:40 PM
4 Jaw Chuck Check your e-mail 71.
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