Mystery #2: ignition timing is way off the mark

[leifanten]

Guys,
when I put my engine back together after repairing my water pump, I replaced the crankshaft pulley with a steel one from Burton (my original had chips in the edge). I ran a complete "find TDC" using micrometers and a degree wheel, and the marks on the pulley aligned perfectly with the marks on the front cover. So far, so good, eh? Now I put the dizzy (pertronix cast flamethrower dizzy) back in and set the timing on the 9 degrees mark. After a lot of huffing and puffing I got it running. However, when I stopped it, the headers were glowing red. I found that the timing was actually way retarded from where it looked like it was. I advanced the ignition to a point where it "feels right". It starts well, throttle response is great, idle is good and it stops with no after ignition and does not "ping".

The mystery is this: when applying the ignition lamp and dialing it back to TDC it reads an advance of 43 degrees. How is this possible? I know the Burton pulley is a little smaller than the original, but that should not matter.

Sorry for long winded post, but it is just so frickin' strange! Could the timing lamp have crapped out in some way?

[rgh0]

I would check for TDC versus the timing mark again. The pully may have moved if it has not engaged the woodruff key on the shaft correctly.

cheers
Rohan

[twincamman]

this happened to me after the last rebuild --started so sweetly ran 40 feet and bucked to a stop ---the clamp had compressed and had not allowed the distributor to seat into the hole and lock in ----thought the thing had blown up ----adjusted the clamp to accept the distibutor base -- clamped it up and its all good now---- ed

[leifanten]

Still in the same place. I need to calibrate my timing light on one of the other cars.

[stugilmour]

Lief:

Don't know details yet, but Ray at RD was telling me on the phone last week that one cannot static time the Pertronix II in the conventonal way. He has included some instructions with the unit, which I should receive shortly. I will send it to you to see if it helps with your problem. Is your dizzy the same as the one RD has listed as a kit under Plus 2 parts?

[m750rider]

Your timing light should be OK if you are checking #1 cylinder and have the clamp around that lead as it inductively picks up the current and signals the lamp to fire when the spark plug does.

I have a Lumenition ignition (electronic system before Pertronix came along) and static time only to get the car running, then dynamic time. I have found that the car runs best for my set up at about 32-35 degrees before TDC.

[Frank Howard]

I need to calibrate my timing light on one of the other cars.

May as well calibrate your air cleaner too.

[leifanten]

Stu,
it is the one that Ray has on his website. Looking forward to what you can tell me.

thanks

[stugilmour]

Lief:

Don't know details yet, but Ray at RD was telling me on the phone last week that one cannot static time the Pertronix II in the conventonal way. He has included some instructions with the unit, which I should receive shortly. I will send it to you to see if it helps with your problem. Is your dizzy the same as the one RD has listed as a kit under Plus 2 parts?

Lief:

Here are copies of the instructions for the coil and the dizzy. A couple of points:

- Based on previous posts, I would wire the dizzy as per instruction point 3, not the diagram. I will run a separate hot wire from the ignition key (White, hot in run/start, unfused) to power the dizzy electronics. Coming off the coil positive as per the diagram will probably cause problems with the tach due to damping in the ignition circuit.
- The instructions do not really say why, but the dizzy must be spinning to be timed properly with the light. This note is a sticker on the instruction sheet, so might not have been clear if the unit was purchased a while ago.
- Looks like the ballast resister can be removed if you are using the Pertronix coil. I did not have a ballast resister in my car originally.
- The dizzy I got from Ray is without vacuum advance. I see Pertronix offers a vacuum advance model for the same cost if this is preferred.
- I added the part numbers for the dizzy to the instruction sheet.

The catalog can be viewed at Pertronix.com

[leifanten]

Thanks Stu,
I have the same one, only with the vacuum canister on it. I run it without the canister connected, as that is how it is supposed to be on the twink. (I am going to call pertronix to hear what they may have to offer of advice as well)

I found an interesting approach on another site (disregard the actual numbers, as they are for an MG, but the method of power tuning looks like a good way to get this right) I will try it out to get the timing set right:


(....power tuning is definitely your best option. Drive the car in 4th gear, wide open throttle from 1500-3000 rpms. Keep advancing the timing until you hear the engine ping, then retard the timing 2 degrees. You may end up with a setting of 14-17 BTDC at idle and that's perfectly fine. That's around a total timing figure of 36 degrees - perfectly safe!!!

(....) If you hear pinging, it most likely going to be between 2200-2600 rpms.....)

[rgh0]

The pertronix system as I understand it works on a variable reluctance principle. An electronic sensor detects the passing magnets mounted on the rotor to trigger the ignition. This detection is done by the passing magnetic field affecting a current in the sensor and producing a signal peak as it passes. Generating this signal peak correctly so the electronics sense it and switch the coil on and off requires some velocity of the passing magnet so it cant be easily timed statically with very very low passing speed of the magnet generated by just turning the dizzy.

However regardless of this if your timing light shows 43 degrees advance at idle to get the engine run properly either the timing light has a problem with its electronics firing the light at the wrong time or the pully mark is no longer at top dead centre.

cheers
Rohan

[neilsjuke]

I have had a rare problem (So they say) with a Aldon that would fire the coil with out the engine turning this was when it was hot so give it a try with a lead from the coil gaped to earth but leave it on for 10 to 15 MINS.
Neil

[m750rider]

To clarify my post

Timing for my 69 S4 with stage II cams and larger sprint valves is best at 32 -35 degrees BTDC at full advance, which will be at 2500 rpm or above.

I have found it a good practice to advance the timing till the engine pings, then work backwards a few degrees.

I have been able to go to 35 BTDC without any problems.

[leifanten]

M750,
that is what I will try out. I have been given some good advice from the tech support at pertronix regarding the sensitivity of proper ground/earth to the dizzy, and how that can make the electronics fire too late, i.e. would require excessive advance to make it right. I am attaching a separate ground lead from the dizzy body to the ground point in the engine bay. I will see how that works once I am done replacing the engine mount for a correct one so my hood will close. Man, that is quite an effort with the cylinder head an radiator back in the car....

[Galwaylotus]

I have found it a good practice to advance the timing till the engine pings, then work backwards a few degrees.

Under load or in neutral while you're twisting the distributor?