need more stopping power. vacuum issue?

[454HO]

Originally Posted by LONGHAIR

The port where your vacuum advance is connected has absolutely nothing to do with the operation of the brakes....unless of course there is a leak.

Not necessarily true. Usually a performance cam likes the timing to be a bit more advanced compared to a stock cam in order to to idle smoothly. This can greatly increase vacuum at idle. So if the engine is set up per factory specs at say 4 degrees initial and ported vacuum advance, then I can imagine that being a MAJOR issue in why the vacuum is low. Such a setup would probably require excessive throttle opening (further reducing vacuum) just to get the engine to run and it would not be running efficiently.

Even if the initial timing were set to something more appropriate for a performance cam, say 14 degrees, the engine still may not run smoothly with ported vacuum advance. If this were the case, moving to manifold vacuum advance could provide the additional timing the engine wants and result in a smoother idle with higher vacuum for the power brakes.

Does this mean the distrubutor might need some work? Of course. And that is why I was asking the questions. But since the original poster has not provided any details on the engine or how it is tuned, all we can do is speculate...

[LONGHAIR]

Originally Posted by 454HO

Even if the initial timing were set to something more appropriate for a performance cam, say 14 degrees, the engine still may not run smoothly with ported vacuum advance. If this were the case, moving to manifold vacuum advance could provide the additional timing the engine wants and result in a smoother idle with higher vacuum for the power brakes.

Does this mean the distrubutor might need some work? Of course. And that is why I was asking the questions. But since the original poster has not provided any details on the engine or how it is tuned, all we can do is speculate...

You can't "just move the vacuum line connection" w/o recalibrating the distributor. Even if that move would increase your vacuum at idle, you would probably get into a pinging situation because of it. If the vacuum really is that low, the advance cannister my not be functioning properly. That will get you an erratic idle, which compounds the problem.

The whole thing seems to me like "too much cam" w/o having the surrounding systems "adjusted" to compensate for it. This could also include the torque convertor. If it is too tight, other issues get involved. He also may be lacking the compression needed to make the cam function too...

My point about switching the vacuum line was more about the fact that it will not "use up" the available vacuum than the technicalities that get over many people's heads.