[screamingchief]

Originally Posted by bubinga

If your close to the edge of suitible vacuum with power brakes or trying to find the edge, you better check your insurance and driving style. I have a can and power brakes and still have issues in parking lots..... the pedal will sometimes be hard as a rock. Once the booster opens the valve, everything is fine.

No offense intended,but that comment just suppoorts TIN TIGR's POV if you ask me.

Power brakes when handicapped with a marginal vacuum supply is often inconsistent and unpredictable,thus somewhat unreliable.

Manual brakes are not,they pretty much react the same everytime,manual brakes are the epitomy of consistency,albeit with a slightly higher pedal effort.

Poorly functioning power brakes are far worse a situation to have than properly operating manual brakes.

Even the factory knew that.

My '72 firebird is a factory manual disc/drum brake car,and it only had a lowly 350 2bbl. in it.

Stops fine.

Originally Posted by bubinga

This the Street section. No vacuum needed for manual brakes, true.... but Pontiac used vacuum to control a lot of other accessories such AC controls, vents/dampers, etc.

Takes very little vacuum to operate the vents and such,and most those systems have their own vacuum resevoir as well,other than an unexpeceted leak affecting their operation,the worst that usually happens with a low vacuum supply is a short delay in the vacuum motor activation.

Vacuum advance,just get the right vacuum can.

Trans modulator,get the right adjustable unit and dial that in.

PCV,find an application that had a low vacuum supply as per OE,and use that valve as it would be calibrated to work with lower vacuum.

Almost every item that uses vacuum has some sort of solution/calibration for a low vacuum supply.

The factory has done such for years,so the answers are out there.

Vacuum is often the very last thing I consider in my cam selection process,that is if I consider it at all.

It means next to nothing to me,it ends up where it ends up,I just make sure to tune the combo for it,and move on to the next item on my list.



Max duration @ .050" for a Street/Strip cam???

The sky is the limit...

I base my cam choices on more relavent influences like intended application,desired performance target,and useable RPM range,static compression ratio,intake and exhaust tract components,head flow,converter,rear gears,that sorta stuff.

And I never look at just the .050" numbers,IMHO that's a huge mistake when choosing cams.

[bubinga]

Originally Posted by screamingchief

Power brakes when handicapped with a marginal vacuum supply is often inconsistent and unpredictable,thus somewhat unreliable.

My '72 firebird is a factory manual disc/drum brake car,and it only had a lowly 350 2bbl. in it.

I agree Bret. I wish mine came with manual brakes since that would solve my vacuum issues. Also it's easier to stop a "lowly 350 2bbl" than a 455 4bbl. My LSA is 110 and 248 intake at 050. (if I remember right) I didn't think I would have an issue.

I didn't mean to get side tracked. Back on topic..... I've heard it said that 240 is the max for power brakes. I think more things are involved like someone said LSA, cu. inches, etc.