[ROVERNET - UK] general timing question

[Paul Smith]

1) The timing specification located in the engine compartment for the  
NADA  3500s is 8 degrees ATC, running at 725-775 RPM, The manual says  
to make all readings at 600 RPM. The difference, I gather, is due to  
the emission control equipment installed for this market. The manual  
states that dwell must be checked at 600 RPM and no greater, or an  
incorrect reading will result. I set the dwell at 26, running at 600  
RPM, adjusted the idle up to 750 to set timing, and checked dwell at  
that RPM as well. Dwell was the same—26— at 750RPM as it was at  
600RPM. Should there be any difference in dwell at a higher RPM?

Theoretically there is no dwell difference at any revs - if points were
perfect swtiches with no spring or bounce or momentum.
However I would be surprised to measure any real diff up to 1500rpm on an 8.


2) I started off timing with too much advance: close to TDC, and got  
some pinging on acceleration, re-set to 8 degrees ATC as suggested,  
and got an occasional skip on acceleration.  I settled on 6 degrees  
ATC for now, with this question: somewhere in the 8 degrees of  
separation between pinging and skipping is the sweet spot, but at  
what point are you too far advanced for the good of the engine's  
health? If I back off just until the pinging stops under load, is  
that the best for performance AND engine life, or is it better for  
the engine (not the driver) to run a bit more retarded?.

For engine life, just getting to no detonation is fine.  If you are running
ATDC then it is likely to be the best spot all round.
I need to find the right advance curve for unleaded petrol for the 2000.
The standard advance curve gives me detonation in the 2000 - 3000rpm range
when it is ok elsewhere.

PVS