[SEL] Economy runs

[Curt]

Rob,
For the sake of discussion I've got a couple of questions for you.
The open / dwell time of the cam can't really be adjusted. By jumping a 
few teeth to retard the opening of the exhaust valve you will also 
retard the closing of the exhaust valve at the conclusion of the exhaust 
stroke.
In general I time an engine missing the timing marks by setting the 
_closing_ point of the exhaust valve so that it closed right at or one 
tooth past TDC. I never pay any attention to where it opens. This allows 
a full charge on the intake stroke.
By doing as you suggest the piston will begin traveling back down the 
bore on the intake stroke, sucking burned exhaust gases back into the 
cylinder before the valve fully closes and only then can the intake 
valve be sucked open.
You will have a leaner charge in the cylinder to compress and fire next 
time around. I gather you have tried this and it worked OK? Is this an 
effective means of getting an engine to run slower in addition to being 
quieter?
I have found that ignition timing has a large impact on the bark of an 
engine. Late timing (to allow very slow running) results in a loud bark 
when the exhaust valve opens, and early timing (factory recommended 
setting) makes for a much quieter bark as most of the burning has occurred.
What have you discovered about adjusting the rocker arm adjustment on a 
Hercules/Jaeger? By unscrewing the adjuster you can effectively lessen 
the open time of the exhaust cycle. This would make it close sooner and 
open later and in conjunction with the retarded cam gear position you 
recommend, have you found this makes for a quieter, slower running engine?
Curt Holland
Gastonia, NC


Rob Skinner wrote:

>Hi Rick,
>Have you tried retarding the opening of her exhaust valve?
>On an engine that just loafs along at slow speed, the valve
>can open really close to bottom dead center with no ill
>effects.  
>
>  
>