Dynamic Ignition timing BN1

[Blowfly]

As a newcomer to this site and a relatively inexperienced Healey owner (admired them for many years but had to wait for a mid life crisis to make the purchase!) I'm looking for advice on dynamic timing an A90 unit. I guess I can crudely mark up the front pulley and timing chain cover. Clearly there is no easy access to the flywheel. How do the "experienced" do it?

 

[Dave Russell]

You can find TDC with a dial indicator in the #1 plug hole & make corresponding permanent notches in the front pulley & timing cover. A more accurate method of finding TDC involves a positive piston stop in the plug hole, a degree wheel on the front pulley, & some calculating to find the actual TDC location.

With TDC marked you can use an adjustable advance timing light to set the timing. Or, you could put additional marks on the pulley & use a non adjustable timing light. The additional marks would be close to .232 inches apart for each additional 5 degrees.

I epoxied a small pointer to the timing cover to line up with the TDC mark on the pulley. Locate the marks so that they can be seen from the top side. Around, between, the fan belt, generator & other obstacles.

BN2 timing covers had a rather poorly defined embossed arrow on the timing cover & a very small dimple on the back inside edge of the pulley to mark TDC.

My factory manual just said to set timing so that the engine didn't ping under load. Better than nothing, I guess.You should probably end up with about 36 to 38 degrees advance at 4,000 rpm, with vacuum advance disconnected.
D

 

[GregW]

I never gave it much thought ‘cause I converted my car to neg. ground, but isn’t there a risk of getting shocked using a “normal” timing light with a metal case on a positive ground car? Hooo, that was a long sentence.

 

[Keoke]

Greg,NO!---Keoke /ubbthreads/images/graemlins/nonod.gif

 

[zblu]

Well, you could pull the plugs, attach a 12v bulb to no 1 lead and and earth and hand turn to see where lite comes on and then see where timing marks on pulley are in relation to the second mark

 

[Dave Russell]

[ QUOTE ]
I never gave it much thought ‘cause I converted my car to neg. ground, but isn’t there a risk of getting shocked using a “normal” timing light with a metal case on a positive ground car? Hooo, that was a long sentence.

[/ QUOTE ]
Short long answer, yes, if you have an old metal cased light. You won't get shocked much but there will be sparks between the light case & any bare metal ground. I just used a fender cover & pay attention to where the light is touching. With a plastic case, no problem.
D