I tried this on the Brakes board with not much help...

My 'Bird's been off the road for about a year, but I now have it almost in running condition. One problem is that when I hit the break pedal, there's what seems to my foot to be normal pressure on the pedal, but I really have to stomp on it to stop. Is that air in the lines, or is something else weird? I know I have vacuum going to the break booster, but could the booster itself be shot? Or is it air in the break lines and i need to bleed them? The front pads have only a couple hundred miles of highway on them, so I know they're fine, and the rears aren't that old. And the breaks worked OK before I put the car in the garage to put the new engine in.

 

Yeah probably power brake booster.

Does it make a "pshhhhhhhhh" sound when you hit the brakes?

 

Does the new engine include a cam with a lot of overlap or very long duration numbers? The lower vacuum produced by such cam installations can grossly affect the amount of power assist you get for braking.

 

It's the Comp XE268. I believe Mark is using the same cam with power breaks with good results. I forget the overlap and duration exactly, but the lift is .477/.480. I'm thinking my break booster is possibly shot... Or is it possible that timing could affect vacuum? It seems the outer ring on my balancer slipped, and I'm not 100% sure where it's timed. I think it's a little retarded, but the engine sounds "ok" when the mark says I'm around 34* advanced, but set it to 0 and the car shuts off and won't restart.... I know, that's a whole seperate problem, but it might be related.

 

Check the rubber hoses on the brakes. They get soft over time and will expand when hitting the brakes making the pedal "feel" ok but not actuating the calipers.

 

Interesting.. Now I know one side of the front should be OK (I blew a wheel bearing on that side and whiped out the whole breaking system there)... BUt I never checked the rest.

 

 

I did the test on http://www.mpbrakes.com/troubleshooting.htm . It appears my booster's OK because the pedal goes down when I turn the car on... I'm still wondering if the fact that the engine's out of time is affecting vacuum, because the cam that I have (XE268) is supposedly power break friendly.

 

did you install the heads your self? I ask this because if you got say the valves open too far It may seem like it runs fine but, you get little vacum, they best way to know if you have sufficant vacum is hook up a vacum guage and see what it reads, you may just have a good vacum leak at a gasket and can't hear it

 

Yes, I did install the heads myself. But how would the valves be open to far, exactly? My father adjusted the rockers, and this is probably the 35 motor he's done that to, so I doubt he overtightened them.

 

Yes, I did install the heads myself. But how would the valves be open to far, exactly? My father adjusted the rockers, and this is probably the 35 motor he's done that to, so I doubt he overtightened them.

 

well, 35 then I wounld say he should have got it right but, mistakes do happen no one is perfect all of the time, I would still lean toward the gasket leak though, because usually you can hear it when the valves are open but, it does happen.

 

also what eng. do you have tpi, tbi carb? If you said I did not catch it

 

I haven't checked the gaskets, but I will. Like I said before, is it possible that vacuum could be screwed up with timing way off? It's reading 34 degrees advanced, right now... I think something's off kilter with the timing mark. My dad thinks I'm a tooth out, but the car runs too smoothly.

 

350 bored .030 over, Speedpro hypereutectic flattops with relief, stock rods and crank, high pressure/regular volume fuel, Comp XE268 cam (kit with springs, lifters, etc), 416 casting heads (saving up for Pro Iron Lightning 180s), Edelbrock Performer RPM intake, Edelbrock 600cfm Carter carb. That's all I could think of.

 

I had a somewhat similar problem on my car, after replacing the booster (never again no matter how bad the brakes get..), it came down to that stupid little plastic, one-way valve the plenum/intake to booster hose connects to. Maybe not the solution to your problem but, not an expensive item to replace to eliminate a possibility.

 

Are you talking about the little white piece or the black piece?

 

Usually black, it is the break booster check valve.

To solve your problem with the balancer, go to Summit and get one of the balancer covers and put it on. They bolt to the inner hub of the balancer where the crank pulley does. Just pull #1 spark plug and crank the engine till #1 is at TDC and install the cover. Since it bolts to the inner hub, it won't matter if the outer ring slips, the timing marks on the cover will always be in the same place.

 

This doesn't really relate to the engine but maybe your rotors and pads are glazed? or maybe the material detiorated from sitting. I know rotors rust (but that goes away with the first few brakings), i don't know what the elements do to a pad. Also, moisture absorbed into the brake fluid may have frozen a caliper or two........

Just a few thoughts

 

Forget about all the timing and gasket leak speculation, and just connect a vacuum gauge to the intake with the engine idling. If you're not making 16" Hg, you could have an issue with brake assist as a result.

Other possible causes are:

As already described, brake hose "swell";

As already described, stuck pistons in calipers and wheel cylinders;

Frozen calipers (rusted to the anchor brackets);

Internal master cylinder leakage;

Sticking or sluggish proportioning valve;

Failing power booster diaphragm or valving;

Damaged reaction disc in the booster;

Oil contamination or glazing on pads/rotors/drums.

But before you go tearing apart the brake system, check the vacuum at idle.