Timing advance

[Summershandy]

I wanted to try some tweaking with advancement but my distributor is now tight up against my oil filler tube. I notice the vacuum diaphragm on a couple other engines sit at around 7 o'clock position where as mine is more like 10. Why would they be different and can it be easily re-positioned or am I looking at a timing mess? 

 

 

 

[JFranklin]

It might relate to the gear mesh at the end of the distributor.

[PONTIAC1953]

your vacuum advance is supposed to be at the 7 O'Clock position, your rotor and #1 cylinder wire should be about the 10 O'Clock position, you'll need to loosen the gaselector clamp to the distributor housing, then rotate the housing counterclockwise so that the vacuum advance is now at 7 O'Clock, then reattach the vacuum line to the advance after you retighten the gaselector clamp, I have no way of knowing where you have the #1 plug wire positioned on the distributor cap now.

[PONTIAC1953]

2 hours ago, JFranklin said:

It might relate to the gear mesh at the end of the distributor.

there is no gear at the end of the distributor shaft, Pontiac straight eight and six engines are designed so that the oil pump shaft gear is timed to the camshaft, and the split shaft of the distributor slides inside the oil pump gear to engage the distributor drive spring installed in the oil pump gear.

[Summershandy]

I see in the manual what you're saying. In this old pic of mine, you can see #1 sits at around 11 o'clock and nothing like the picture. Sometimes I wish I was a pro at tearing down engines and put things where they belong but I'm not. I'm sure it's not as simple as rotating the shaft and re-installing the wires. I'm not about to cause any damage to the internals. 

[Bloo]

         

21 hours ago, Summershandy said:

I wanted to try some tweaking with advancement but my distributor is now tight up against my oil filler tube. I notice the vacuum diaphragm on a couple other engines sit at around 7 o'clock position where as mine is more like 10. Why would they be different and can it be easily re-positioned or am I looking at a timing mess? 

@pontiac1953's post  pretty much nailed it, but I would add the following for clarity.

 

How the oil pump gear is meshed determines where the rotor is pointed when #1 is firing, and if you need the rotor pointing a different direction when #1 fires, you need to change the clocking of the gear by removing the oil pump. If this is wrong, the position of the #1 wire needs to remain at the same clock position no matter what, until you pull the oil pump. In most cases this detail is unimportant to make the car run right.

 

Changing the position of the CASE of the distributor and the vacuum advance has no such limitation. For instance, in your picture your vacuum advance is banging on the oil filler pipe, and you want to be able to turn it more clockwise, right?

 

You could rotate the distributor housing counterclockwise exactly one tower (or 2 towers, or 3 towers or whatever, but lets say one). After rotating the housing counteclockwise one tower (1/8 turn), you would move the plug wire positions all clockwise one tower (1/8 turn). In doing so, your #1 wire winds up in exactly the same clock position it was before. It's relationship to the rotor position has not changed, and the car never knows the difference. Your vacuum advance is now 1/8 turn left from where it was before.

 

Of course eyeballing one tower is not terribly accurate. It is probably good enough to get the car started, but then you would need to set the ignition timing with a timing light, or mechanically, or however you normally do it.

 

 

Edited August 27, 2022 by Bloo (see edit history)

[john hess]

mark. . looks like your wires are off one position.... pull your #4 wire out of the distributor..... leave disconnected..... pull #1 wire and install.... next, #6, put in #1 hole... move each wire one hole... #4 will be your  last wire.... reset distributor to correct position with a timing light.... should correct your misalignment..

[john hess]

what bloo said.... we both post at same time.....

[Summershandy]

 What both you and John shared I can picture now. Turn the distributor counterclockwise and move the ignition wires the same amount. Got it. This would merely change the position of the vacuum advance. While I still got everyone's attention....does anyone know if I have the H.C. head or standard head? H.C. is the 3 degree mark on the harmonic balancer and standard head is 6 degrees. I believe when I initially checked the timing, I used the middle mark or the 3 degree mark. 

Soon as I get a decent day I'm gonna give it a try. I picked up an old Sears timing light off buy and sell but hate using it. I have to wear rubber gloves and not touch any of the body or I get, ZAP, ZAP, ZAP......lol

 

[john hess]

automatic transmission usually has hc head.... should be forged in head left rear corner top...

[john hess]

it will say "high compression"

[Summershandy]

Guess it's been a while since I've crawled around the engine and memory hasn't gotten any better!