15-11-2017, 04:19 AM
Unless blatantly wrong or outdated, I think it preferable to stay with handbook procedures. This reduces the confusing diversity of info presented to newcomers. Although it is tedious to access the flywheel, the book method avoids the risk of significant over advance. If strangers are going to drive a car generous max manual advance is best not available.
At part throttle generous advance improves economy, but no one drives Sevens at part throttle!
The full manual range seems to be 25-30 deg depending on the lie of the linkage. Even for hand cranking spark does not need to be as late as tdc, so even with 20 deg full advance rarely retard beyond half way. The range of the early Ruby auto distributor, from stop to full rpm was only 6 crank degrees. As most pulling in Sevens is done using rpm, advance is near full most of the time.
Much depends on whether have a new relatively forgiving nitrided crank or not, and close clearance mains. Crank stress increases very rapidly with advance, and life is hugely decreased by increased max stress. The performance trade off for modest advance is often slight.
On my car at "speed" the spark could be moved aver a considerable range and the only thing which changed was the exhaust note and engine din.
At part throttle generous advance improves economy, but no one drives Sevens at part throttle!
The full manual range seems to be 25-30 deg depending on the lie of the linkage. Even for hand cranking spark does not need to be as late as tdc, so even with 20 deg full advance rarely retard beyond half way. The range of the early Ruby auto distributor, from stop to full rpm was only 6 crank degrees. As most pulling in Sevens is done using rpm, advance is near full most of the time.
Much depends on whether have a new relatively forgiving nitrided crank or not, and close clearance mains. Crank stress increases very rapidly with advance, and life is hugely decreased by increased max stress. The performance trade off for modest advance is often slight.
On my car at "speed" the spark could be moved aver a considerable range and the only thing which changed was the exhaust note and engine din.