# Distributer install and timming



## gtoearl (Dec 21, 2009)

Installed the distributer yesterday. Have the rotor pointing to # 1. I couldn't remember just where the vacuum advance unit was positioned when I took the distributer out a number of months ago. My question is: does it matter? I looked at some pictures of 389 motors and it seems that the vac advance position is different and the cap screws are also in a different position..... But, again I have the #1 piston at the top and the timing marks are aligned. Also, any idea what I should set the timing? I've seen all kinds of ideas on the web... book calls for 6 degrees....but I've seen anything up to 28 degrees... Help please...


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## BearGFR (Aug 25, 2008)

Orientation of the vacuum diaphragm does not matter - much. As long as it allows you to move the distributor however you need to in order to set timing. (Factory orientation, if you're curious, had the diaphragm pointed across at the drivers side fender). #1 plug wire on the cap is next to the firewall, towards the middle of the car. As far as running, as long as all your wires reach and you have everything wired "in time", it doesn't matter.

Timing. Topic of much discussion  Factory specs indeed called for 6-degrees initial (vacuum diaphragm disconnected, hose plugged, idle rpm set to spec). Realize and understand though that what your engine really "cares" about are two things: 1) total advance under load (wide open throttle, engine loaded) and 2) how quickly (or slowly) that advance "comes in". The purpose of that vaccum diaphragm is to add more advance under light load / cruise conditions for economy and cooling purposes, but it's a 'secondary' concern. There are several threads on here about setting 'total' advance and what that's all about. I know I've written about it a few times myself. You can probably locate those posts using the search tool. Short version: your distributor has a mechanism of weights and springs inside it that allows it to "add" advance as rpm increases. How much, and how quickly it comes in, is adjustable to a point and may have been altered at some time in the past by a previous owner so you have to figure out "how much" advance is "in" yours. Every engine is going to "like" a certain amount of total advance for peak performance, and that point is going to vary from engine to engine. It's influenced by combustion chamber shape, piston top shape, materials (iron or aluminum) and other factors so no one can tell you what's going to be the opimal setting for your engine. In very general terms, most Pontiacs with factory iron, open chamber heads tend to 'like' something in the neighborhood of 34-36 degrees total by about 2500 rpm. So if there's 28 degrees of travel built into the distributor, and you want a total advance of 34 degrees --- 34-28=6 degrees initial timing will get you there. Again that's just an example. Your engine might be different. Mine is... my distributor has 20 degrees of travel in it, I know from experience and testing that my engine (aluminum, open chamber heads) likes 36 degrees of advance, so I set my initial timing to 36-20=16 degrees.

Bear


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## gtoearl (Dec 21, 2009)

Thanks for the info. A lot to take in. I'll do my best to get this thing timed correctly.


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## BearGFR (Aug 25, 2008)

You'll also want to make sure that your timing marks on the balancer and timing cover aren't lying to you. I've seen brand new balancers and covers be off by as much as 6 degrees. The easiest way to verify is to use a degree wheel and top-of-the-cylinder piston stop (while the heads are still off) during assembly, but it can be done with the heads on if you know exactly what you're doing. Checking and setting total timing can be a little unnerving if you're not used to it and aren't careful - because you're setting it and working closely around the engine while it's spinning merrily at 2500 rpm or so. You need either an ACCURATE timing tape (and the aforementioned accurate timing marks) or a "dial back" timing light to do it ( similar to one of these: Amazon.com: INNOVA 5568 Pro-Timing Light with Tool Case: Automotive, 
http://www.autozone.com/test-scan-a...light/actron-digital-timing-light/718068_0_0/ ) They have an adjustable delay circuit in them that you use by turning a knob/pressing a button to "move" the timing marks while you're reading them (engine running) until they appear to be lined up at 0 TDC, then you read the actual amount of advance at that setting from an indicator on the light. So if you wanted to set your engine to say, 35 degrees total, you'd dial that setting into the light, disconnect and plug the vacuum connection, loosen the distributor hold down enough that you can turn it with some effort (but not so loose that it's going to move around on its own with the engine running), have a friend hold the engine steady at 2500 rpm or so (most all of these lights also have a built in tach), while you adjust the timing by turning the distributor until the marks appear to be at 0 TDC. Tighten the hold down and then repeat the process to make sure nothing moved. THEN after you've got that done, set the light back to zero and use it to measure the advance setting with the engine idling. This is so that the next time you need to set the timing, you know what setting at idle corresponds to 36 degrees at rpm so you'll be able to set it at idle without having to spin the engine up again. That is, as long as you don't change distributors or alter yours in ways that change how much internal advance travel it has. (After you're all done, don't forget to reconnect the vacuum advance.)

Why do you disconnect it? Because you're trying to simulate the conditions that the engine operates under when the car is moving and you've got your foot in it. When the engine is at wide open throttle under load, there is no manifold vacuum (well, to be 100% accurate there has to be a smidge otherwise there'd be no air flowing into the intake - but it's a tiny amount and it's nowhere near enough to activate the vacuum advance mechanism). It's not possible to recreate this condition with the car sitting in your driveway in neutral, so we simulate it by disconnecting the vacuum line in order get as close as we can to it.

Bear


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## chui1980 (Jun 5, 2013)

BearGFR hit it out of the park. I have being complaining about my 326 acceleration of the line and yesterday I did get it right finally. One of the things that must be taken into consideration is what Bear said. Your vacuum advance must be located in a way that allows you to move back or forward so that you can set it as you please. Point distributors must have the access window towards a location where allows you to set if needed. That is way vacuum advance must be towards the driver fender side and your distributor points window access towards passenger fender so that you can adjust both. Whether you point rotor to #1 piston or towards fire wall what really maters is that the wires are properly installed at each piston and distributor on a counter clock wise rotation 1-8-4-3-6-5-7-2.


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## gtoearl (Dec 21, 2009)

Thanks for all the info. Have another question for you. On my engine I On my engine I have a timing chain cover that appears to have three timing marks. My problem is the crankshaft damper appears to be from a 65 389. According to motors manual the damper that I have my problem is the crankshaft damper appears to be from a 65 389. According to motors manual the damper that I have as to timing marks on it. Hope that makes sense, what do I reference to set the timing. Another quick one , The distributor is set into the engine with the advance pointing in the wrong direction as I stated before, I really need to change that and put it where it should be as it seems to be in conflict with the mounting of the coil. it's been a while since I did this kind of install. I know I need number one piston at top dead center, my question is Install. I know I need number one piston at top dead center, my question is Do I simply turn the shaft at the bottom with a screwdriver to orient the position of the distributor. Do I simply turn the shaft at the bottom with a screwdriver to orient the position of the distributor . Maybe if you can just give me the procedure to install the distributor correctly would make more sense thanks for all the help guys.


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## gtoearl (Dec 21, 2009)

Well, today I fired up the engine. Took a bit to get the engine to start. My problem is it seems to stall below 1500 RPM. I'm thinking the timing might be part of the problem. I took the number one spark plug out and turn the motor until I was at top dead center To see where the timing marks are. Seems there real close but not exact. Could that be my problem. Can I be one or two teeth off on the distributor? It was a very hot day today and the engine heated up rather quickly. I was able to keep it running at about 2000 2200 RPM for about 5 minutes. But each time I lowered the idle down from the throttle the engine would die. I'm thinking it might be some bad gas. The gas in the gas tank is about a year and a half old. Or could it simply the timing. Bear, you've been very helpful, appreciate some help.


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## BearGFR (Aug 25, 2008)

Sounds like it just needs to be timed, Earl. Do you have a timing light? It's nigh unto impossible to time an engine "by eye" - by that I mean just visually lining up all the marks. That will generally only get you into the ball park where it will at least start and run. Getting things dialed in requires a light. Try adding a little advance (turn the distributor body clockwise) just a smidge or two, see if that helps. If you were off one or more teeth with respect to how the cap and everything is wired up, I doubt it would run at all.

Bear


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## PontiacJim (Dec 29, 2012)

gtoearl said:


> Well, today I fired up the engine. Took a bit to get the engine to start. My problem is it seems to stall below 1500 RPM. I'm thinking the timing might be part of the problem. I took the number one spark plug out and turn the motor until I was at top dead center To see where the timing marks are. Seems there real close but not exact. Could that be my problem. Can I be one or two teeth off on the distributor? It was a very hot day today and the engine heated up rather quickly. I was able to keep it running at about 2000 2200 RPM for about 5 minutes. But each time I lowered the idle down from the throttle the engine would die. I'm thinking it might be some bad gas. The gas in the gas tank is about a year and a half old. Or could it simply the timing. Bear, you've been very helpful, appreciate some help.


If the gas is 1 1/2 years old, you definitely have bad gas in it. Today's ethanol blends go bad quickly if they sit -6 months is not good in my opinion. I would not run the engine on that gas for fear it could even damage the engine. Drain the tank and fill with fresh gas. I would also not do any more timing adjusting until I got the good gas first as bad gas could be affecting everything.

Typically, if your engine gets real hot quickly (you can watch your temp gauge climb before your very eyes), your timing may indeed be retarded and you need to advance it. 

Your balancer and timing cover need to be matched. If you install an early balancer on a later timing cover (or vice-versa), your timing marks will be off. I don't remember off the top of my head which grouping of years go with each, but I am thinking the balancer and cover were changed for either '67 or '68. I posted on this in another post, so you want to verify yours match each other.:thumbsup:


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## gtoearl (Dec 21, 2009)

Bear, thanks for all your advice I have the motor running. You were right, it was the timing and I think I was off by one tooth. I removed the distributor and rotated it And reset all the wires after putting the number one At top dead center. Anyway, trying to download a video to show you but evidently you can't do that ...


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## BearGFR (Aug 25, 2008)

:thumbsup: Awesome - glad you got it going

Bear


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