TR2/3/3A Question about points.

[doc50]

I installed an 'Advanced Distributor' unit in my rebuild. After 1,000 miles, I just checked the gap and found it to be over what's called for.

I'll guess it was around .020. I set them to .015 and it starts and runs better.

My question is simply this: How does a wide (...or narrow...) point gap affect running, and how many thousandths can the gap vary?

Thom
1959 TR3
#TS34909L(O)

 

[Geo Hahn]

Any change in the gap will also change the advance, e.g. a wider gap will cause the points to open sooner, hence more advance. Smaller gap, vice versa.

 

[CJD]

Also less time for the coil to energize with a larger gap. That would reduce the spark strength at higher RPM, although I doubt it would be too noticeable with 4 cylinders and the speeds we run.

 

[doc50]

Thanks, Geo and John. Any thoughts as to how much gap is considered too much?
I think my points were around .020.
(Correct gap is .015).
I feel that the car is peppier now with the change to .015.

Thom
1959 TR3
TS34909L(O)

 

[TomMull]

I'm not sure there is a number since there are several variables; condition of the coil, capacitor, point surface, and spark plug gap, to name a few. However, when the gap gets wider, the dwell shortens and the coil has less time to recover. In addition, the voltage required to spark across the wider gap also increases providing a weaker spark. (too small a gap does not provide enough spark volume)
In my experience, I've not detected any difference in driving between .015 and .020 and I'm sure I've had them well above the latter. However, the less noticeable differences like track times, fuel economy, point and plug life are significant.
The gap window for peak performance is quite small.
Tom

 

[Geo Hahn]

Thanks, Geo and John. Any thoughts as to how much gap is considered too much?

Well, at some point the points would not close at all - that would be too much

I wouldn't think you'd feel much difference in normal driving with a .015 v .020 but perception is everything.

The usual failure mode I have experienced is a closing gap - due either to wear on the block that rides against the cam or a set of points that have not been secured tight enough.

 

[doc50]

Good 'points', Tom and Geo.
Regarding perception....I am a firm believer in the 'placebo effect' so I'm convinced that it runs better than it ever has from that little change in gap!