03-06-2021, 03:47 PM
(03-06-2021, 02:54 PM)Nick Lettington Wrote: Rough rumbling and back firing? Now thst sounds familiar... I suspect that you may want to re-check the ignition timing.
It surprised me how far out the timing can be on a running engine.
I agree with Nick. Having played the Youtube clip of the running engine, I would say that the timing is too advanced. A high compression head does not need as much advance as a low compression one, as the flame front has less distance to travel. I recall that my special, with a much planed Cambridge head growled like a pig if it had more than about 8 degrees of advance. By contrast, my RP, on a slightly 'wedged' standard head is perfectly happy at 20 degrees.
I would set the timing initially to TDC and then manually advance the distributor until the engine is just sounding rough and then back off the distributor until it just doesn't. If your car has a manual advance and retard, set the mechanism so that this position is the maximum advance on the lever. If an distributor with automatic advance, wedge the bob weights to their most advanced position before setting the timing. Unwedge them after the timing is set.