[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.

[screamingchief]

Originally Posted by rad400

I would like to keep it hyd non roller, cause I don't have a budget for hyd roller.

IMO your combo is screaming for a healthy flat tappet solid cam,crower #60310 comes to mind right off the bat as a sound choice.

Might even be able to pull off the Crower #60311 solid to be honest,you got the CR,convertor,and gear for it.

A solid any bigger @ .050" than those and you would have to tighten up the LSA,and that change would kill off the vacuum others are so concerned with.

But I digress for now,let the debates continue.

Bret P.

[Ron H]

I agree with Bret about the solid flat.
The U/D 280/288, 247/255 @ .050 on a 110 LSA is a great street/strip cam in your area.
I ran 12.11 @ 112 3700 lbs at 5800' DA, 6x ported heads, rpm intake, dougs headers, 3.89 gear, 28" tire.
1.65 rockers, stud girdle.
Beauty, eh?

[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.

[Region Warrior]

Originally Posted by Ron H

I agree with Bret about the solid flat.
The U/D 280/288, 247/255 @ .050 on a 110 LSA is a great street/strip cam in your area.
I ran 12.11 @ 112 3700 lbs at 5800' DA, 6x ported heads, rpm intake, dougs headers, 3.89 gear, 28" tire.
1.65 rockers, stud girdle.
Beauty, eh?

Now you have worried.
I was gon'a try some'tn close to yours.
Mine went 12.10 @ 112.74 last year with a 461/ RAIV top end with 2 collasped lifters.
3565 lbs/th400/3.42/27.5 tires.

[Ron H]

More than likely I was 4000' higher in DA than you would be?
Many have seen mid to upper 11's with similar set up.

[67 Lamnas]

Originally Posted by rad400

Thanks, for the replys just seeing if I could go higher then the crower 60210 I have in there now. Was looking at the comp 292h. Even though some say street pontiacs don't like single patteren cams, and run power brakes.

67 lemnas whats hydroboost brakes?

A Hydroboost system uses hydraulics instead of engine vacuum for power assisted braking.....the hydraulics are generated from the power steering pump.

[70judgeconv]

I run a vacum pump on the inside of the driver side fender. It is bolted to the inner fender. This works great.
My street car runs a 248-256 solid cam. It has great street manners with 355 gears and 2800 stall. All this in a #3995 70 lemans runs well into the 11's driven 200 miles each way to the track. It all depends on the WHOLE combination of parts not just the cam and heads.

[screamingchief]

Originally Posted by bubinga

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.

Well,that's what the car had in it when I got it,it now has a 455 with ported #96's.

Still needs a few things done to get it back on the road,just keep finding new problems as I solve the old ones.

Too many projects,,,too little cash...

Plenty of time though.

Still expect it will stop fine,even with the 455 in it.

All my other manual brake cars stopped fine,some with disc brakes,some with drums.

Agree that if I just had to have power brakes,I'd opt for the hydro-boost option,and not look back,it's well proven & trusted technology,as it was used on numerous OE applications already.

I personally dislike vacuum assisted power brakes,always have,always will,JMO/FWIW.



BP.

[llwta76]

Originally Posted by screamingchief

IMO your combo is screaming for a healthy flat tappet solid cam,crower #60310 comes to mind right off the bat as a sound choice.

Might even be able to pull off the Crower #60311 solid to be honest,you got the CR,convertor,and gear for it.

A solid any bigger @ .050" than those and you would have to tighten up the LSA,and that change would kill off the vacuum others are so concerned with.

But I digress for now,let the debates continue.

Bret P.

My UD 288/296 solid / flat w/108 lsa and the low 7.5" vacuum is a testament to that. Although my vacuum operated brakes have more positive action ( ever since going to a smaller dia. booster) every once in a while (about 5% of the time) the vacuum in the booster seems to go south and I loose the vac. assist. I've had cams w/ 8" @ idle and never a vac. brake issue. I imagine that cam in a 400 would carry a vacuum lower then 7" and idle @ 1200rpm +. Not good w/o a can. Larry

[71 Ventura II]

FWIW The old technology 292H is a decent cam but you would like the price and performance better running the Isky 292 Mega cam IMHO. The Isky is ground on a 108 LSA and will work great plus Summit sells it for much less than the Comp stuff. See what you think! JD

[Skip Fix]

the hydraulic 304/312 I believe was 247/255 @ 0.050 I had it on a 112LS.

I will say I tried a solid flat tappet 288/292 UD. Pulled to 7000 BUT when I swapped on a single plane the brakes weren't always there. Were OK with the dual plane HO intake

[DiamondJim]

Originally Posted by 67 Lamnas

A Hydroboost system uses hydraulics instead of engine vacuum for power assisted braking.....the hydraulics are generated from the power steering pump.

Another vote for hydroboost. Run the cam you want. -Jim

[Region Warrior]

Now i'm think'n i need more cam.

[llwta76]

Originally Posted by Skip Fix

the hydraulic 304/312 I believe was 247/255 @ 0.050 I had it on a 112LS.

I will say I tried a solid flat tappet 288/292 UD. Pulled to 7000 BUT when I swapped on a single plane the brakes weren't always there. Were OK with the dual plane HO intake

I had that problem w/ my UD only since swapping my rpm to a T11. The hood scoop on my 76 T/A likes the lower single plane but my booster likes the RPM. Gonna switch back! Larry