Tunning for Spark advance

[Doc 1]

Doc,
I've got one last question for you, and my purposes here will come to a close. It is another factor, maybe; I'd like to know if case vacuum has an affect on the advance curve? Lets say you built a motor with a short stroke, long rod, big bore configuration, and hooked up a vacuum pump to a relay that kicked in at a certain RPM only, would THAT affect the advance curve? Am I talking about pumping losses here? I know this is in far left field fwiw.   

Thank you.

If you where building a EVO, Shovel, Pan, or Sporty the case vacuum would be an issue and yes a vac pump or two would help greatly to improve power. However the Twin Cam is a internal breathing motor and there is no case vacuum as the pistons travel up the cylinders or too much pressure in the crankcase as the pistons travel down the cylinders. The air moves from the crankcase into the cam compartment, and vise versa, through the large case bearing....so I would say no, a Vac pump is not necessary nor would it help to gain power.
Vac pumps are generaly used to provide better ring seal for better power at higher piston speeds. Pro Stock Harleys and some Modifed Harleys classes used the concept of vac pumps at the drags.
Doc

[HogBag]

Doc 1
Have you ever tuned any bikes with a before and after Singh grove. From what I have read this is supposed to help torque with a cleaner running motor with better fuel consumption. A win win for any engine builder ? whats your call on the Singh groves as a engine tuner.   

[Doc 1]

Doc 1
Have you ever tuned any bikes with a before and after Singh grove. From what I have read this is supposed to help torque with a cleaner running motor with better fuel consumption. A win win for any engine builder ? whats your call on the Singh groves as a engine tuner.

There has never been any proof that the groves actually do anything at all, however, if it makes you feel better to have them go for it because there is no proof that they hinder the performance either. Personally I think they are snake oil at best.
Doc

[HogBag]

Doc1
Thanks for the advice on the groves. It's one of those things I want to try but there's no way a can take a hacksaw to good set of flowing heads.

[FSG]

but there's no way a can take a hacksaw to good set of flowing heads.

Pass it to me, I'll do it for you.