[Healeys] BN1/BN2 Timing

[Dave Russell]

Hi Alan,

Not sure what arrangement you may now have on the A90. Some only had a 
mark on the flywheel, very difficult.

If you are so lucky as to have a TDC mark on the front pulley, a small 
dimple near the top inside of the back belt groove, and an embossed 
arrow on the front of the timing chain cover, this will locate TDC.

If no marks, accurately locate cylinder #1 at TDC, place a paint mark on 
the pulley which aligns with the embossed arrow, if no arrow, place a 
corresponding mark or pointer on the timing chain cover.

Measuring around the pulley circumference clockwise as viewed from the 
front, each 0.235" is equal to five degrees. I would mark each five 
degrees up to 35 degrees or 1.65".
The pulley measurements are assuming that your front pulley diameter is 
5.380". If different, recalculate the .235" = five degrees measurement.
(5.38" diameter X 3.14 = 16.89" circumference. 16.89"/360 degrees = 
.0469" per degree & 5 degrees = 0.235")

The timing really should be set with a strobe to about 35 degrees at 
4,000 rpm, vacuum advance disconnected, for two reasons.
1- The total centrifugal advance in your distributor may be unknown or 
not accurately specified.
2- If the high rpm timing is over advanced there can be "silent 
detonation" (unheard because of other noises) which can be very 
destructive to the engine. Set the maximum advance at high rpm & let the 
idle & lower rpm numbers fall where they may.

Regards,
Dave Russell



Alan Seigrist wrote:

>Hi All -
>
>For various reasons I shall not get into, I have never actually
>determined the timing on my BN1.  I gave it to my mechanic several
>years ago and asked him to sort it, and he painted lines on the crank
>pulley and timing cover and I've never had to worry about it since.
>
>Well now I'm in the situation with my A90 (same motor as the 100), and
>I need to time the car.
>
>---  By the way I've replaced the ancient Lucas dizzy on this car
>with a Pertronix EI dizzy, so I can't really watch the points as part
>of this process.  Any simple ideas?
>
>Thanks!
>
>Alan