Brakes and a cam?

[Craig 94 TA GT]

Ever since my new motor, I noticed my brakes are so-so. The 9" rear made my ABS is INOP and I used to be able to lock them up with the Baer 2 piston caliper/rotor kit. Not that it's a good thing, but it shows the grabbing power they had prior to the new engine Now, it seems that the brakes got 2x to 3x weaker. They still stop ok, but I can't even come close to locking them up. When stopping, you can push the pedal hard and the car still doesn't stop that hard. It feels that I gained about 1000 lbs. I've thought that they might need bleeding (the engine builder pulled the whole bottom end suspension off to get the motor out, so the brakes were completely off). But now I'm reading that a cam might affect the vacuum for the brakes. The cam is a smog cam though, mid 220s, 113 LSA, so it's really mild. Could a cam like this affect the power of the brakes on the stock master cylinder?

[Joe 1320]

I can't tell you based on the grind. Take a vacuum reading, if it's 14" minimum at idle, chances are that you're OK. below that and things degrade quickly.

[Craig 94 TA GT]

Thanks Joe, I'll check it out. I had another close call today - there was a sudden stop in front of me (thank goodness I don't tailgate), but I had to floor the brakes as hard as I could to get it to stop. It just doesn't have the stopping power right now.

[Jeff_in_Atl]

Something you can do is put a reserve can on the vacuum system. Oddly enough my Mom's old Mercury Grand Marquis had one on it from the factory. Weird. I'm not sure how much that would really help.

I know you are diligent about what you do but is it possible there might be a vacuum leek somewhere?

[Craig 94 TA GT]

Jeff, that's a very good idea - it definitely might have one. I have inspected everything over and over, but who knows - it could be somewhere I didn't look. Jeff Creech, the tuner, said that the MAF readings were a tad low when I took it WOT, so I'll see the vacuum to make sure there's not a leak. Thanks.

[FTA1995]

Tighten that manifold down again maybe? I just clean and re-gasketed my whole top end and got 2-3 inches more of vacuum just from that. If you really can't find it and you're that concerned, get an electronic vacuum pump and use that for the brake booster, should work great.

[Injuneer]

Measure the vacuum under various operating conditions, and post the results. As Joe noted, if you have the vacuum, you shouldn't have a problem.

I wouldn't expect a problem with that cam from the basic specs. Overlap kills vaccum and I don't think its an overlap hog. My setup is 230/242 114LSA with almost 0.600" lift and I see 16"Hg at idle and the brakes work fine.

Did Jeff Creech say the MAF or MAP readings were low at WOT?

[Craig 94 TA GT]

Would something like this work?
http://www.sears.com/shc/s/p_10153_1...d=vacuum+guage

Jeff mentioned the MAF readings and stated "And the car isn't eating as much air as it should for the mods. (MAF shows this) so need to check things like clean air filter." That's after I was running mediocre 12.4-12.7 times at 106-108. Since then, I've thrown out the small/heat soaking vortech elbow and repaired a .25" deep dent in the exhaust. Not sure if those will make a difference.

Your cam is way bigger than mine so I suspect if you're fine cam, I should be too cam-wise...thanks for your help!

[Craig 94 TA GT]

I just tested it and saw 13" at first. After a few seconds, it flucuated between 13 and 14". It looks like with the lope of the cam, it would just flucuate between 13 and 14 at idle the whole time. Desired hot idle is 850 RPM. I revved it up a few times and got up to 20. I didn't test it driving though.

Also, if it's worth to note, fuel pressure reads 40 psi at idle. Pulling the FPR vacuum line off makes it read 46 psi.

[Injuneer]

13"Hg sounds a bit on the low side. Put it under load on the highway and it may not produce the braking power. Maybe measure the vacuum under hard braking to see what happens. If you have a scanner, you can look at MAP and the barometer numbers and vacuum is the difference between the two numbers.

The fuel pressure is OK.

[Craig 94 TA GT]

I haven't had a chance to do some real tests yet, since the new a-arms are taking so much time to get right, but I did a few things. First, I checked the intake manifold bolts (got to 9 out of 12) and most were at least 30 ft lbs. There was one that was way low, but I was able to tighten them to 35.

I measured vacuum at idle again - this time cold idle, 900+ RPM and vacuum was now 12?? The hoses looked fine, but I only had about 20 min to check things. I'll check again soon.

[Craig 94 TA GT]

I still haven't figured out a way to get the gauge taped to the dash, since the hose is short...I'll try to see it under hard braking soon.

I pulled the plugs to see if maybe one was loose and saw a few things that might draw a flag. First, about 3 of them looked perfectly fine. 3 of them had orange on the ground electrode, and #8 was was completely white. Does white indicate a vacuum leak? The Haynes seems to indicate it, or too hot. One thing though was that the plugs were improperly gapped by the shop. They were between 0.057 to 0.060. I set them all to 0.050 when I put them back in.. They are TR-55s.

One more thing I was thinking of - the dyno shop had also readjusted the rockers and only applied thread locker to the rocker studs. The heads are so far ported, the stud holes are exposed to the intake ports. Is it possible that this white (or orange/white) plugs have a vacuum leak?

Attached are pics - the orange one is the least orange of the 3. The 2 were way more "orange" than this one. Thanks again.