Brakes not working after sitting over a year.......

[PQ]

What are the chances that the factory stall is being overpowered by the cam?

[CFD]

Originally Posted by PQ

What are the chances that the factory stall is being overpowered by the cam?

I don't think the converter would affect it, mine's a 3600 stall.

[TommyTheCat]

I think the bigger cam is definitely going to be causing the vacuum problem just because the car has been supercharged.

Get a vacuum pump or power steering assisted brakes instead of vacuum assisted... if there is a kit. I completely forgot your car is SC

[Mr Twisty]

How many separate vac lines come off the S/C? Have you plugged them then checked vac?

[CFD]

Originally Posted by PQ

Mine is no longer an L99. New pistons, rods, cam and all. Built back forged and with a lower compression ratio. But only .3:1 lower.

I could check back at the booster valve but not sure why that would change. I did measure Bonnies from there as the LS2 Vette has the freaking booster hose tucked way back under the firewall shelf.

Car never had brake issues at all before.

The L99 reference was for it being an automatic mine is also an LS3 conversion with the exception of VVT.

[thahemp]

So what makes the idle/coastdown behave differently in the auto cars? I imagine it's because you don't separate the driveline completely when coming to a stop. I haven't hooked up to an automatic car yet. It's on my todo list.

[CFD]

Originally Posted by thahemp

So what makes the idle/coastdown behave differently in the auto cars? I imagine it's because you don't separate the driveline completely when coming to a stop. I haven't hooked up to an automatic car yet. It's on my todo list.

That's what I'm thinking woild be the difference, on mine if I roll down the driveway all is fine, in gear is when there is an issue, could be as simple as the drop in idle speed. I don't tune so I'm not sure, just a thought.
.

[thahemp]

It should use the coastdown table if you're moving with your foot off the gas. I could see how you would need a bunch more timing to keep it happy. Mine would bog if I didn't have a clutch to feather.

[motorhead]

PQ, I've been keeping an eye on your thread, but I haven't posted because I couldn't think of anything other than a vacuum problem. It looks like that is what you're finding , but not the root cause. I'm thinking that maybe you are making a very slight amount of boost that is reducing vacuum but yet not showing a positive at idle. Maybe the supercharger bypass isn't working properly or not tuned correctly for your set up.

[Redemption]

Originally Posted by motorhead

PQ, I've been keeping an eye on your thread, but I haven't posted because I couldn't think of anything other than a vacuum problem. It looks like that is what you're finding , but not the root cause. I'm thinking that maybe you are making a very slight amount of boost that is reducing vacuum but yet not showing a positive at idle. Maybe the supercharger bypass isn't working properly or not tuned correctly for your set up.

This!

Bypass on my whipple went bad and reeked havoc on damn near everything. Make sure it is opening and closing properly.

Mine had a hole in the diaphragm, causing vacuum leak and no boost.

[Chevy Fanatic]

Originally Posted by PQ

So here is the situation.

As many know my car has been sitting since June last year (2013) when the cam went bad and ruined my engine.

Well it's all rebuilt and upgraded and I have finished everything but tuning.

By all indications I should be able to drive it nicely to the tuners.

So I fire it up and want to check that it's good to go and drive it around the block. Get to the end of the driveway and it's got little to NO brakes. Was in reverse so I got it stopped but barely. Had light brakes until the pedal would go no more. (NOT floorboard but a solid hit plenty above where I know it COULD go)

I pull back up and seems like even less brakes. (I put a bigger cam in it than previous and 1st gear is stronger)

No engine codes as far as booster sensor.

So here's what I've checked.....

There are no leaks. Pedal stops solid and does not go any further anyway.

Fluid is full.

Brake booster is hooked up to vacuum.

Sensor is hooked up properly.

So could my caliper pistons be rusted shut?
Could it be the brake booster valve stuck?
Could I be in the twilight zone?

Everything went together well but this is the first hurdle I've faced. I WANT MY CAR BACK.

If it were mine I would get a tune done before trying to further diagnose, you may not have a problem. Your problem could be all in the tune.

[PQ]

Originally Posted by motorhead

PQ, I've been keeping an eye on your thread, but I haven't posted because I couldn't think of anything other than a vacuum problem. It looks like that is what you're finding , but not the root cause. I'm thinking that maybe you are making a very slight amount of boost that is reducing vacuum but yet not showing a positive at idle. Maybe the supercharger bypass isn't working properly or not tuned correctly for your set up.

Oooohhhhhhh ****!!!!!

I completely forgot another and only other difference .........

I took the 1:1 pulleys off the back and went with an overdrive set.

You guys thing that is it???

[PQ]

Originally Posted by thahemp

So what makes the idle/coastdown behave differently in the auto cars? I imagine it's because you don't separate the driveline completely when coming to a stop. I haven't hooked up to an automatic car yet. It's on my todo list.

Ok, this coastdown thing. What is it? Could it be the reason that it still tends to want to die after I back up as I take it out of reverse and go to drive?

[PQ]

Originally Posted by Chevy Fanatic

If it were mine I would get a tune done before trying to further diagnose, you may not have a problem. Your problem could be all in the tune.

More than likely what I'll do. I burned 2/3 tank of gas in about 150 miles the last two days. hahaha

14 month old gas and no tune.