Ported heads/big cams affecting braking?

Greg Hazlett

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GI-you are saying the spring in the BOV was bad? I am going to swap mine out, I need a 6 psi one...hopefully that will help.
 

GI Joe

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GI-you are saying the spring in the BOV was bad? I am going to swap mine out, I need a 6 psi one...hopefully that will help.
It was not bad just the wrong size for the lower vacuum so it would not hold the valve in position. Once i got the right spring it actually picked up a little vacuum
 

Greg Hazlett

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Ok, that makes sense...I am seeing 11 vac at idle and the spring I have in there now is too big which is also leading to the fluttering....going by the Tial chart for the Q BOV I need the black 6 psi spring.
 

8306gt

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Ok, that makes sense...I am seeing 11 vac at idle and the spring I have in there now is too big which is also leading to the fluttering....going by the Tial chart for the Q BOV I need the black 6 psi spring.

Actually it makes no sense as you don't have vac at the blow off valve except from the line you are using to hold it open. If you are leaking vac from the valve the diaphram would have to be bad and changing a spring would not fix your issue.
 

gil_t2

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Just a thought, does the musteng have oneway vac valve to the booster? If not try one, it is a cheep fix. You said that you replaced the brake pads, Did you resurface the rotors? You may have glazed the pads. Just something to double check.
 

GI Joe

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Ok, that makes sense...I am seeing 11 vac at idle and the spring I have in there now is too big which is also leading to the fluttering....going by the Tial chart for the Q BOV I need the black 6 psi spring.

Yep # 6 is what i used and it fixed both issues
 

GI Joe

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Actually it makes no sense as you don't have vac at the blow off valve except from the line you are using to hold it open. If you are leaking vac from the valve the diaphram would have to be bad and changing a spring would not fix your issue.

And if the vacuum is a bit low at the valve and unable to overcome the spring it will hang too closed and allow too much air flow to the throttle body opening it a hair and causing the issue of lower vacuum. Seen it a few times including my own car. Tricky tricky
 

8306gt

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And if the vacuum is a bit low at the valve and unable to overcome the spring it will hang too closed and allow too much air flow to the throttle body opening it a hair and causing the issue of lower vacuum. Seen it a few times including my own car. Tricky tricky

So what you are saying is that you were actually slightly pressurizing the intake at idle or low rpm causing a decrease in engine vac which does make sense. I misunderstood as I thought you were saying you were leaking vac and by changing the spring you stopped the leak rather than allowing the air from the blower to escape to atmosphere at low rpm, cruise.
 

GI Joe

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Yep. And the other indicator is the surging

Greg you can just cut the spring one inch at a time til you get there. Old trick from turbo guys
 

Greg Hazlett

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Guess it is hit or miss on Ebay..I looked on there and Amazon and did not see any of the Q style springs on there.

Understand about cutting a coil but I plan on selling the spring I have now...don't think the perspective new owner would appreciate that, LOL!
 

JeremyH

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Just a thought, does the musteng have oneway vac valve to the booster? If not try one, it is a cheep fix. You said that you replaced the brake pads, Did you resurface the rotors? You may have glazed the pads. Just something to double check.


Yes it has a check valve.
 

s8v4o

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I was unaware of this until Jeremy drove my car and said he thought the brakes were not stopping the car as well as they should, esp with the upgraded pads/lines on it.

A couple of things here...

YOU never noticed a lack of braking before.

Someone who doesn't drive your car all the time said they're not up to snuff

You're running Hawk pads. Not sure which ones but most heavier duty pads need heating before optimal performance is achieved.

Is it possible the other guy has factory stuff and just isn't used to your setup on YOUR car?

You may be chasing a hypochondrial problem.

EDIT - is the other guy lightblade?

EDIT #2 - Yeah man it's REALLY hard to compare the two vehicles brake setups. It's almost like driving a 600HP boosted setup then driving a lowly 400hp NA setup and say something is wrong because it feels slow. Just saying. Maybe someone with a factory brake setup should take it for a spin and see what they say about the brakes.
 
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JeremyH

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A couple of things here...

YOU never noticed a lack of braking before.

Someone who doesn't drive your car all the time said they're not up to snuff

You're running Hawk pads. Not sure which ones but most heavier duty pads need heating before optimal performance is achieved.

Is it possible the other guy has factory stuff and just isn't used to your setup on YOUR car?

You may be chasing a hypochondrial problem.

EDIT - is the other guy lightblade?

EDIT #2 - Yeah man it's REALLY hard to compare the two vehicles brake setups. It's almost like driving a 600HP boosted setup then driving a lowly 400hp NA setup and say something is wrong because it feels slow. Just saying. Maybe someone with a factory brake setup should take it for a spin and see what they say about the brakes.

My reccomendation as well, also vice versa, drive a car with full vac to see the difference in braking force and pedal feel.

It really seems like an issue that most people just deal with and get used to.

Having the brake stiffen up and pushing it really hard to the floor and then continuing to roll until the car stopped where it wanted, past where I intended to stop is definetly an issue to me. But then again if I had more experience driving his car and new how the brakes respond I could have started braking harder earlier and get used to them. Note I was only cruisng at 15mph when I tried to stop the car. Was not a fun feeling at all.

All that aside a bunch of things are happening here. Greg didnt feel any problem with the brakes as he drives the car alot. He was having trouble getting the linelock to hold, most of the time the car would push through, he also wasnt getting alot of rpm on the convertor while holding the brakes and the gas at the line before the car starts rolling at the track. He has 10-11 vac at idle. And then I mentioned my experience driving his car where i felt like it wasnt going to stop. His rotors look new and basicly are, he has hawk hps pads that dont need to be heated up to work, and they are already bedded in with the rotors and he has ss lines all 4 corners so these are nice upgrades over stock. All of these are factors that point towards power brakes that arent completely up to par due to the low vac IMHO.

But i didn't want him to take just my opinion so I reccomend that he start a thread to get ideas and also to drive Ray's car and Ray drive his to see if they notice a difference on each other's cars.
 
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