Setting timing

[drooartz]

Spent some time last night trying to set the static timing on the Tunebug. I used the Haynes manual as my reference, and keep in mind that I've never done this before. Took a while to find the timing mark, but I think I found it.

Once I figured I had it set, I cracked open the factory manual and saw that it says to remove the vacuum line from the distributor before setting the timing. I didn't know to do this. Do I need to go back and reset the timing now, with the vacuum line off?

This is on a stock 948 motor, BTW.

Also, any other hints for setting the timing? I'm not really sure how to know when it is right.

 

[jlaird]

Yes timeing should be set with vacume line off of the Dizzy and pluged up on the mainifoud/carb side. A golf tee may work stuck in the rubber end of the line?

 

[dklawson]

Well... yes and no.

With static timing the engine isn't running so you don't need to disconnect the vacuum advance. The disconnecting and plugging of the vacuum lines is important when setting dynamic timing at idle.

I don't play golf so I use sharpened pencils to plug the vacuum lines.

As for tips on setting the timing, are you talking about dynamic or static settings? For dynamic settings, just pay attention to the idle RPM and the vacuum lines and you'll be fine following your Haynes manual. There are no tricks. For static timing, there are a couple of things to keep in mind.

The A-series engine distributor has a rotor that goes CCW. To set the timing, pull or bump the engine over ONLY in the normal direction of rotation to remove play in any of the timing chain and components. If you overshoot the timing mark, rotate the crank back through at least 30 degrees then go forward slowly to the marks. Once the static timing marks are lined up, rotate the dizzy body CCW until the points are known to be closed (plus another 15-20 degrees of rotation) then SLOWLY rotate the dizzy body CW until the points just open. As before, you are trying to take out all the mechanical play by overshooting the rotation and then only rotating components in their normal running direction to keep the play out.

 

[drooartz]

I'm just playing with static timing at this point, one thing at a time. Doug, what you described is essentially what I did, so now I feel more confident that I set the static timing correctly.

Do I need to play with dynamic timing as well? Not sure what the difference is, really, other than that the engine is running with dynamic. Timing still seems a bit of a black art to me.

 

[Trevor Jessie]

I've never set static timing (other than when setting up a new distibutor... even then I just get it close for start up). I usually set dynamic timing at idle, then check my mechanical advance(plugged vac. advance) at about 4000 rpms and set the timing at 34 degrees advance. This works with most cars. But, I'm not a real mechanic... I just play one on the weekends.

 

[jlaird]

The final test of course is dynamic, the engine running, etc, etc.

 

[lesingepsycho]

The best way I have found to set dynamic timing is thus:

I lined up the timing marks at top-dead-center. I then transfered the marks to the top left side of the engine on the timing cover by scratching a mark into the cover and then filling in the scratch with a more visible color of paint, bright white so that it would really shine under the strobe. Then, if you get yourself a timing light where you have an advance knob, then all you have to do is set the timing light to the value you want and then adjust the distributor until the TDC marks line up again. So for dynamic idle, i set the timing light to 10degrees (or whatever the manual says, I forget exactly) and then adjust the diz until the TDC marks line up, then I do the same for the mechanical advance, I set the light to 30degrees (or whatever) and make sure the marks line up again at the specified RPM.

In all honesty however, the BEST way I have found to set the timing is, get in and drive it, feel how it accelerates and then pull over, tweak the timing a little bit and drive it some more, etc, until you achieve the best performance, although I realize that might not be a satisfactory method for many people.

JACK

 

[Kurtis]

[ QUOTE ]
In all honesty however, the BEST way I have found to set the timing is, get in and drive it, feel how it accelerates and then pull over, tweak the timing a little bit and drive it some more, etc, until you achieve the best performance, although I realize that might not be a satisfactory method for many people.

[/ QUOTE ]

I agree... I have a timing light, but never use it. I just time at fast idle (1500-2000 RPM) for maximum RPM, retard slightly (until I get about a 100 RPM drop) then drive it. If it pings under heavy acceleration in high gear, I retard a little more until it stops pinging. If it doesn't ping, I advance a little until it does ping, then back it off.

 

[drooartz]

By biggest problem in all of this tuning is that I have no real point of reference for how the car should perform. Other than obvious stuff like "it doesn't run" or "it boils over every time" I just don't know what to expect. 948s are not fast, but how not-fast is normal? This is really the only old car I've ever dealt with (brief fling with a TR4 not withstanding).

[ QUOTE ]
I just time at fast idle (1500-2000 RPM) for maximum RPM

[/ QUOTE ]

For dynamic timing, I'm lost here. Am I running the engine with the distributor loose enough that I can turn it? If you are at a fast idle RPM, how do you time for max RPM... you're already at a particular RPM...

I'm feeling a wee on the ignorant side today... /ubbthreads/images/graemlins/tongue.gif

 

[Trevor Jessie]

He's suggesting that you set the timing by ear.
Run it with the dist loose enough to turn.
Disconnect and plug vacuum.
turn fast idle one to about 1500 rpm.
turn dist to get the idle to pick up and smooth out.

Personally, I don't trust myself to hear the pinging, so I set the dynamic timing with a light that has an advance knob. And yes... the dist. is loose enough to turn.

 

[Kurtis]

Yes Drew... leave the distributor loose, then turn it in the direction that causes revs to increase - usually in the advance direction if you've statically timed it. At some point, after you advance too far, the revs will begin to drop. At that point, retard the timing slightly. You're just positioning the distributor so that you get the highest RPM you can. At this point it will be a little advanced, so retard the timing so that you get an RPM drop of about 100. At that point, it's close enough to drive and fine tune.

It should be mentioned that no matter how you set timing, the final step should always involve actually driving the car and adjusting the timing on the road.