Wednesday, July 6, 2016

Ignition Timing

So having built my new engine and getting the car legally roadworthy, now comes the task of making it nicer to drive. If you read the previous post, driving to the MOT garage was awful, the car had no power and didn't want to know at all on hills. To fix this the engine needs tuning up and that starts with the ignition timing, apparently... so I've read!!!

Timing is everything!!
Before I got started, I wanted to make sure that the timing bracket I made in this post here was set up correctly. I really should have done this when I installed the bracket, but I only just realised after reading up on the subject what the teeth on the timing scale were for. So in terms of calibration, I wanted to make sure that the notch on the pully aligned with the longest tooth on the scale when the engine was at TDC.

Thankfully I marked the TDC point on the flywheel when I fitted it and also chose a bell housing cover with a little spy hole to see inside. To rotate the engine, I always lift one of the front wheels off the ground, put the car into 4th gear, remove the spark plug leads and simple rotate the elevated wheel by hand, watching in the spy hole for the mark I made.

Once it was perfectly at TDC, I had a look at the position of the notch and... oh dear, it was out by about 4 degrees!!

The only way to resolve this was to remove the timing bracket and subtly 'encourage' it into a new position with a few nudges in the vice, After a little trial and error, it was exactly where it was supposed to be. I even painted the tips of the teeth to make them more visible.

I did notice though that if I move my head up or down, it altered the alignment resulting in a parallax error of about 2 to 4 degrees which was a bit rubbish. To resolve this, I picked a point on the radiator and marked it with a spot of silver paint to represent the angle of observation. As long as I always line this spot up with the largest tooth on the timing scale, it would eliminate any parallax problems.

If you read the section in the Haynes Manual about ignition timing, it goes into a detailed step by step explanation about 'static timing', which sounds rather involved and complicated. Thankfully this method is for a pre-1976 engine and as mine is a 1987 engine complete with timing marks on the pulley, I'll be using the strobe gun method, which is far easier thankfully.

The only downside to this method is of course, you'll need to shell out a little cash in order to buy a stroboscopic timing gun. On the plus side, you do get to use the word stroboscopic, which I think more than makes up for it! Shopping around, I found a myriad of different types and prices, but after careful consideration, (ie, which was the cheapest!) I found a bargain basement, bread and butter, basic model on eBay for a little over £15. Can't argue at those prices!!

When it arrived I could see that it has 3 wires and although the supplied instructions were very basic, it's pretty self explanatory. The two crocodile clips are the 12v power supply for the lamp and the remaining wire with the slider, simply wraps around the HT lead going to cylinder 1. To simplify things even further, I decided to power the lamp with a 12 volt supply from my jump start pack as it seemed easier than fiddling around trying to connect the relatively large clip to the small connection on the positive side of the coil.

Connect the power
Attach the spark sensor

As I was pretty keen to get started I attached the wires and fired up the engine and to my horror, nearly smashed the spark sensor to bits as it was resting on the alternator fan. Luckily I got away lightly as there was very little damage done, but it did make me realise that it was a pretty stupid thing to do.

After reading the Haynes Manual on the subject, I had a vague idea of what I was actually doing. The manual said to disconnect the vacuum advance pipe and set the revs to 1500 RPM, once all that's done you can start playing with the strobe and take the reading.

After warming the engine up, I decided the easiest way to set the engine to 1500 RPM was to fiddle about with the choke and do my best to get the rev pointer as equally as I could between 1400 and 1600 RPM.

Once that was done and the vac was pulled out of the distributor, I was ready...

Pointing the strobe gun down the gap between the fan and the timing cover, I was amazed to see the static image of the timing mark on the lower pulley as clear as day. It was somewhat harder to get a decent photo, but I tried my best and eventually managed to get this seemingly static image showing the timing scale and the timing mark on the pulley... and it was miles out, in fact, it wasn't even on the scale!!!! This was actually my initial reading before I calibrated and painted the teeth on the timing scale.

After slackening off the distributor retention bolt, I was able to rotate the dizzy round and observe the notch on the pulley move accordingly. After a little tinkering back and forth, I was able to set it somewhere in the region of 8 to 10 degrees before TDC. I even managed to get a better photo this time.

And that's really all there is to it. Once the dizzy was bolted back up and the vacuum hose reconnected, it was all done, and the engine did indeed feel better for it after a quick blast up the road. I'm pretty sure it will feel even better still once I've tinkered with the fuel to air mixture as I'm sure it is running rich at the moment, and to help with that, I finally get to play with my Colour Tune gadget I bought a while back, but that's for the next post...

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