wrd1972

iTrader: (12)

Those track results were not with my current setup, not even close. I dont disagree that a different cam could do better.

With regards to the track times, the car has only been to the track one time in its life and that was 2.5 years ago when it had valve float (replaced the cam), misfires due to bad wires and clutch slippage. I also did not even have long tube headers at the time. That said, all of the performance issues are now fixed except for the fat 4050 pounds of car with my fat *** driving it. Lets just be fair for a change and look at the total picture.

The only other time prior to that I actually ran at a track was once in 1989 on a bone stock GT. Its fair to say I likely cant drive a stick car as well as 95% of the folks on the board so before we start into a cam bashing thread and my car is **** lets assume that a decent driver can run the car significantly better than I can. If any one of you guys tracked it, you would certainly do better especially since its running right. As I have said countless times before, I dont race this car, its just a fun fast hobby car that consumes too much of my money but satisfies my needs at present. If time and money presents itself in the future, I would like to try a different cam.

Back on topic.
Okay you guys got me thinking so lets reset here.
The 8" vacuum reading was taken by hooking a Mityvac to the nipple on the intake for the opti vent. I also have a Datamaster in the car and it says something different.

The Datamaster shows BAR at 29.6" and the MAP is showing bouncing readings of 16.6" -17.2" so lets just call it 17" for discussion sake.
Does this mean my real engine vaccum is ~12.6" or so and my Mityvac gage is damaged and simply is not accurate?

RamAir95TA

iTrader: (2)

It stands to reason that your Mityvac gauge isn't accurate. Get a real manifold vacuum gauge and see what the results are. They're like ~$30.

wrd1972

iTrader: (12)

I pulled the cover off of the Mityvac guage and it is certeinly damaged. Gears are stripped and parts are corroded so hence the inaccurate readings.

So if the Datamaster is saying the engine has 12.5" of vaccum, should a accurate vacuum guage read the same thing when connected to the nipple on the intake for the opti vent?

speed_demon24

iTrader: (6)

Idle vacume shouldn't even be that important, especially with a 6-speed. You should be pulling a good 20+" on each shift and as long as your booster is in good shape it shouldn't be that noticeable that you have a cammed car.

wrd1972

iTrader: (12)

Agreed. Its easily doing that.

joshh123

iTrader: (1)

hmmmm

SS RRR

iTrader: (2)

So, before you put the pump on, did you ever press on the brakes when you were pulling that much vacuum?

wrd1972

iTrader: (12)

Yeah and under those conditions it was fine. Remember the old booster had a leak bad enough it would bleed off very rapidly due to this:


The picture above only shows one of several deep gouges that were on the booster shaft and causing whatever vacuum was stored in the booster to rapidly bleed off. The gouges were caused by the wrong spec retainer clip used in an aftermarket (OEM spec) brake master cylinder. Simply put, the wrong retainer clip that had ears on it, cut the gouges in the plastic booster shaft when the pedal was pressed. The correct retainer clips does not have ears.

Moving forward. When I was cruising down the road for several miles at low vacuum condition, the booster had far less vacuum in it than what the motor was seeing. If the motor was 12.5" of vacuum for example, there was much less in the booster and when you hit the brake pedal, it was rock hard and difficult to stop. In fact it was downright scary at times.

If I was in high vaccum conditions and promptly hit the brake, it worked fine because there was not enough time for the booster to bleed that high amount of vacuum off.

I finally figured all this out when I got the pump and had it all plumbed into the booster for testing. Once the pump was turned on, the pump motor would kick in, out, in roughly every 30 seconds like clockwork without ever applying the brakes. I also clearly heard the leak and traced it down to the shaft you see above in the pic and addressed the problem with the MC retainer clip and got a new booster. In fact I got the booster and a new better MC for free when I went back to the parts house and showed them that their MC damaged my brake booster.

So as you can see, the brakes worked well under some conditions and shitty under others because of the damaged leaky booster. I knew from searching that many here had engine vacuum of 12" and they claimed there brakes worked fine. But I thought I had 8" of vacuum. The unfortunate fact that the Mityvac guage was a mile off lead me in the wrong direction to believe it was just low engine vacuum so I blamed the cam in error and went in the direction of the vacuum pump thinking that was the solution.

SS RRR

iTrader: (2)

I am pulling 11" of vaccum and my brakes work fine. I think I see you had already installed the pump when you put in a new booster? If so, have you turned the pump off to see if the new booster can handle the brakes?

wrd1972

iTrader: (12)

Yeah the pump was nicely and cleanly installed prior to determing the old booster was busted. If I leave it in, it will still ensure there is never less than 15" of available vacuum to the brakes. So obviously there is no drawback leaving it in other than the weight of the pump.

Yeah I am gonna pull the fuse and turn it off and see if there is any difference once the weather gets good. I am completely expecting the brakes to work perfectly fine.

wrd1972

iTrader: (12)

Well I bought a real vacuum guage and the motor makes 12.5" - 13" vacuum at idle. I also pulled the fuse from the pump and saw no noticable difference in braking. Clearly the busted leaky booster and inaccurate guage on the Mityvac led me in the wrong direction. All is good. Thanks all.