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

[TommyTheCat]

[PQ]

Well They got stronger in drive and I can drive the car but in reverse it's not really much better.

I removed both front calipers and retracted the pads/pistons. The calipers are working like normal. As I got more of the year+ worth of rust off they seems to begin to clamp better BUT...........................

Having measured our Jeep and Vette here are the results..........

Our Jeep (3.7L V6) is running 13.5 inches vacuum.
Our Vette (LS2) is running 16 inches vacuum.

My car is running 8 inches vacuum.

So while it has gotten better as far as stopping power it's still not where it needs to be.

I measured mine on my boost gauge (always knew that but didn't want to depend on that reading, turns out it is spot on) and at the supercharger vacuum port.

[PQ]

There have been much bigger cams installed and not much talk of vacuum pumps. What gives here?

Keep in mind the intake pressure is showing this reading on the rear of the manifold and at the vacuum stem.

[CFD]

Originally Posted by PQ

Well They got stronger in drive and I can drive the car but in reverse it's not really much better.

I removed both front calipers and retracted the pads/pistons. The calipers are working like normal. As I got more of the year+ worth of rust off they seems to begin to clamp better BUT...........................

Having measured our Jeep and Vette here are the results..........

Our Jeep (3.7L V6) is running 13.5 inches vacuum.
Our Vette (LS2) is running 16 inches vacuum.

My car is running 8 inches vacuum.

So while it has gotten better as far as stopping power it's still not where it needs to be.

I measured mine on my boost gauge (always knew that but didn't want to depend on that reading, turns out it is spot on) and at the supercharger vacuum port.

It may have something to do with the cam and tune. I am not blown but run a GPI SS4 cam, when I start up in the am I have little stopping power when backing out of my driveway, which is on a steep hill, only takes a couple of minutes and all is normal, as soon as the idle stabilizes. If I roll down in neutral all is fine. Never did that with my previous cam. Your sounds to be a similar issue. When I get to the shop tomorrow I will measure my vacuum just for comparison because I'm curious right now. Does your vacuum reading vary when first starting in comparison to when warmed up?

[PQ]

Originally Posted by CFD

It may have something to do with the cam and tune. I am not blown but run a GPI SS4 cam, when I start up in the am I have little stopping power when backing out of my driveway, which is on a steep hill, only takes a couple of minutes and all is normal, as soon as the idle stabilizes. If I roll down in neutral all is fine. Never did that with my previous cam. Your sounds to be a similar issue. When I get to the shop tomorrow I will measure my vacuum just for comparison because I'm curious right now. Does your vacuum reading vary when first starting in comparison to when warmed up?

Wow, mine is fine in neutral in reverse as well. Interesting. Same in drive I'm sure.

Not sure what the cold and hot measurements are. I'll have to check them. Now that I know my boost gauge is accurate it will be easy.

[CFD]

Originally Posted by PQ

Wow, mine is fine in neutral in reverse as well. Interesting. Same in drive I'm sure.

Not sure what the cold and hot measurements are. I'll have to check them. Now that I know my boost gauge is accurate it will be easy.

I'm not sure how mine is in drive on cold start in the am because I always pull in forward and back out. The other thing is I don't recall it being like this until my tune was changed. It's still not dialed in because I have no friggin' time. lol. I may just change my habits and back it in to see if it's like that in drive on the cold start.

[thahemp]

Man it seems really unlikely that the cam and tune would cause that problem, but I guess you never know till you check. I run just 14* of idle timing on my 10* overlap cam and have no issues with braking. Not even a noticeable difference from stock. I'm interested to see how this fleshes out.

[thahemp]

I should say... 14* idle timing, 14* coastdown timing, and just over that for HO... it's blended pretty close down there.

[CFD]

Originally Posted by thahemp

Man it seems really unlikely that the cam and tune would cause that problem, but I guess you never know till you check. I run just 14* of idle timing on my 10* overlap cam and have no issues with braking. Not even a noticeable difference from stock. I'm interested to see how this fleshes out.

You wouldn't think so but it is possible. The other thing is yours is an LS3, PQ's and mine are L99's, idle characteristics are a bit different.

[Southern Comfort]

What if you tried measuring vacuum with the booster hose unplugged from the booster?
Not sure what your cam failure did but what if it pressurized your vacuum system and ruptured a diaphragm? Dont forget there's other stuff that could contribute like BAP and cruise actuator maybe...

[CFD]

Originally Posted by Southern Comfort

What if you tried measuring vacuum with the booster hose unplugged from the booster?
Not sure what your cam failure did but what if it pressurized your vacuum system and ruptured a diaphragm? Dont forget there's other stuff that could contribute like BAP and cruise actuator maybe...

I don't think it's a damaged diaphragm as it wouldn't change after warm up.

[Southern Comfort]

I missed the warm up part info somewhere. Hope you get it worked out soon.

[PQ]

Originally Posted by CFD

You wouldn't think so but it is possible. The other thing is yours is an LS3, PQ's and mine are L99's, idle characteristics are a bit different.

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.

Originally Posted by Southern Comfort

What if you tried measuring vacuum with the booster hose unplugged from the booster?
Not sure what your cam failure did but what if it pressurized your vacuum system and ruptured a diaphragm? Dont forget there's other stuff that could contribute like BAP and cruise actuator maybe...

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.

[CFD]

Originally Posted by Southern Comfort

I missed the warm up part info somewhere. Hope you get it worked out soon.

It's puzzling for sure. Mines not an issue because it's very drivable, the similarities are peculiar though, PQ's on the other hand needs to be figured out.