setting base timing without a light?

If one were going to set their base timing on a mechanical/vacuum advance distributor without the aid of timing marks, how would you do it?

At this point I've disconnected the vacuum line and hooked up a vacuum gauge to the manifold... I let the car warm up and idle down. I advanced the distributor until vacuum started to drop, then I retarded it until vacuum dropped. At that point I set it about 3/4 of the way between the two points but more towards the advanced side. Seems to run pretty well.

Thoughts?

Put the engine at TDC, and add a pointer & paint mark on the crank. Use one of those adjustable timing lights & set full timing @ 2500 rpm (or wherever your weights max out at).

We did that on the spridget race engines all the time - The stock timing marks are waaaay underneath the engine, behind a crossmember.

KJ

Kendall_Jones wrote: Put the engine at TDC, and add a pointer & paint mark on the crank. Use one of those adjustable timing lights & set full timing @ 2500 rpm (or wherever your weights max out at). We did that on the spridget race engines all the time - The stock timing marks are waaaay underneath the engine, behind a crossmember. KJ

I like it. How much do these cost?

$35 from HF : timing light

KJ

If its an old school simple distributor and the timing is close enough that it ready will start and run you can use a vacuum gauge connected to manifold vacuum. With the vacuum line for thethe distributor disconnected and plugged adjust the base timing to the highest reading on the vacuum gauge, that will be a good base timing set point. On newer ignition systems I don't know if that method will work or not.

If this is a points type distributor:

With the engine off, set your engine's timing marks to the advance you want. 5degrees = set the pointer to the 5 degree mark on the pulley with the #1 piston at TDC on compression.

Get your test light out (not timing light, test light, you do own one, right?). Hook the clamp to battery positive and take off the distributor cap.

Loosen the distributor and put the probe tip on the terminal on the case of the distributor (the coil negative connection).

Rotate the distributor until the light -just- goes out. If the rotor turns clockwise, turn the distributor housing counter-clockwise, if the rotor turns counter clockwise, turn the distirbutor housing clockwise.

You want the points to open exactly when the crank is at the desired degrees of advance. This collapses the field in the coil and makes your spark.

If it's an electronic unit, best to do it with the vacuum gauge.

You really should buy a timing light.

If it's all out power you want, advance the distributor until you get detonation under load, then back it off a couple degrees from that.

Shawn

I have a timing light, but BMW uses a single flywheel timing mark which is set at 4000 rpm. I want to be able to make changes to test out different settings.

I'm wondering if my mechanical advance isn't aggressive enough. I can advance the distributor until it starts to miss at idle and vacuum drops, but I don't get any pinging at all under heavy load.

For the single mark, you just need to do the math. 360 degrees in a circle, right? Just figure out the circumference of the pulley and mark accordingly.

If the car has a knock sensor, it'll catch detonation long before you do.

You could use an advance timing light, a tach and the marked pulley to make your engine it's own distributor machine.

34 degrees is considered the maximum amount total advance, you can get away with more but generally speaking, power drops off after that.

Here's what I would do if I were you.

Forget about your vacuum advance if this is a track car. It will really only be a benefit for fuel economy.

Find out how much mechanical advance you have in the distributor with the timing light. Rev the engine at idle and see how much more advance you have from the idle advance setting and rework the distributor to gain the extra advance you want.

Set the idle advance to give you the most power from idle to about 1500rpm. You can do this fairly well with the SOTP dyno or a G-tech.

Then dial in the rest with your weights, springs and stop plate.

There will be a stop in the distributor you can play with which will limit your total advance. Sometimes you can rig something up with a setscrew to make it easier to adjust.

Use the weights and springs to set how fast the advance comes in. Lighter springs will make the advance come in at lower rpms, Heavier weights will make the curve ramp up quicker. Balance the two to make a curve you want.

You will probably want everything in by 2000 rpm to make the fattest torque curve you can.

Use a graph to plot the amount of advance in 50 rpm steps using your engine as a distributor machine along with the timing light and tach. This will show you the advance curve.

You'll probably need to fiddle with it for a while until you get the feel of it.

Alternatley, find an old codger who has a distributor machine and make friends with him.

I have one at home and one at work bu I doubt the trip to Canada is worth your time.

Good luck!

Shawn

You learn something new every day.

http://www.youtube.com/watch?v=qwMUf4bRy2c

So cool!

I just did that with a bud's 97 Altima. Just rotated it until it started, and got it where it just sounded right. I loaded it up in gear and was happy with the throttle response, so we drove it to my house for the OBD-2 scanner. 20 Degrees. It's supposed to be 18-22. Not bad!

Alright, so get this... First off, my idle is sometimes rock solid at 850, and other times about 1200. I have yet to find the issue. It seems to go with the cycles of the moons.

I tried to set the timing based on the BMW specs with my light and the flywheel window. They claim that with my distributor, at 4000 rpm, a "ball" should appear in the window. No such ball, I was only able to find a line. It's annoying the way it's set up. No scales like on all the other cars that I have owned. I did notice that at idle the timing jumps around quite a bit (with or without vacuum source hooked up). But when you give it gas, timing goes rock solid but increasing.

Anyway. I drove it around for a bit, it felt slow. 0.31gs on my accelerometer.

I hopped out and advanced the distributor until it started to stumble at idle and then I backed it off a little bit. 0.31gs on my accelerometer.

Thought I was hearing light detonation, so I got out, and cranked it so far retarded that the idle dropped to 850 (from my random high idle). Car started to smell like gas, but I got in it and ran it again just to see if the 'detonation' went away. 0.34gs on my accelerometer, and the sound was not detonation.

Also, I ripped apart my spare distributor today, and there is no easy way to change the amount of mechanical advance.

???

Trans_Maro wrote: If this is a points type distributor: With the engine off, set your engine's timing marks to the advance you want. 5degrees = set the pointer to the 5 degree mark on the pulley with the #1 piston at TDC on compression. Get your test light out (not timing light, test light, you do own one, right?). Hook the clamp to battery positive and take off the distributor cap. Loosen the distributor and put the probe tip on the terminal on the case of the distributor (the coil negative connection). Rotate the distributor until the light -just- goes out. If the rotor turns clockwise, turn the distributor housing counter-clockwise, if the rotor turns counter clockwise, turn the distirbutor housing clockwise. You want the points to open exactly when the crank is at the desired degrees of advance. This collapses the field in the coil and makes your spark. Shawn

That is pretty damn cleaver

Well, today I took some time to make some (a?) timing tape for my engine. Got it installed and set my base timing. This is going to be an excellent diagnosis tool. It's incredibly easy to read. I positioned my own pointer made from an old clothes hanger about 1/4" above the crank pulley. The tape looks like this:

I printed it onto some masking tape and stuck it on to test it. Works incredibly well.

Right off the bat I found out that my base timing was FAR too advanced. I set it to about 13* at idle just to test it out. Car pulls much better everywhere, idles at the right speed, and throttle response is better.

Although, it only seems to gain about 10 deg of mechanical advance up to about 4k and then it slowly drops to about 5 deg mech advance. OEM spec calls for more. Taiden spec wants 2983479287349823 deg of mechanical advance.

I also have an older version of the distributor which appears to have much more mechanical advance. So I may have to try that one out and see what happens.

here's another pic of it. It's lifting already because I didn't use anything to really hold it down. I'm going to do it again tomorrow and actually stick it on well.

What is it in the distributor that is limiting the amount of advance?

Can you post a pic of the advance plate and weight assembly? Maybe I can point some stuff out.

Shawn

Well, I had written out a huge thing about how it's not adjustable, but to be completely honest I haven't removed the advance plate from the shaft. But I will tell you this, if the arms swing out any more they will contact the case.

make a piston stop out of an old sparkplug body with a ground off bolt jammed into it.. put it in the #1 cylinder and gently turn the engine one way until it hits.. put a mark on the balancer inline with something that makes a good reference point.. turn the motor over the opposite direction until it hits and make another mark.. true tdc is exactly halfway between those points. you can then use a cheap plastic protractor to make some timing marks..

to set your base timing without a light, you just turn the motor over in it's normal direction of rotation until the mark lines up with where you want it.. loosen up the distributor and hook up a spare spark plug to the #1 plug wire.. turn the distributor until it sparks.. tighten down the distributor.. there, your initial timing is set, but you'll need a light to check your total timing and map out your advance curve- which means you can set your initial timing with the light...

Thanks novaderrik, but I have it figured out now.

Although, it is funny, the screwdriver TDC trick doesn't work on this engine. The spark plug holes are about 10* from horizontal so I would touch the opposing cylinder wall before I would touch piston.

You can grind down the outer edges of the weights, just make a template so you do each one evenly.

Then run lighter springs to make up for the reduced weight in the distributor flyweights.

I would disassemble that advance mechanism and have a look underneath. You've probably got a tab or stop under there which limits the amount of total advance and keeps the weights from hitting the case. You should be able to modify that stop a bit to allow for more advance.