Cam experts... (Why does the car push through the brakes with a cam in an auto)
06-26-2010, 10:55 PM
#41
This is me explaining the best way I can understand it.
The cam is surging. Basically the same thing that happens when you run too low of a gear and the converter locks at say 35mph with a big cam.
I'm going to guess it isn't pushing through the entire time? Or at least more noticeable when on the hit of the cam? That is just an assumption.
Before I got my white car dyno tuned (ms4 cam) it would surge at red lights and almost die at times. When the cam hit (especially when it almost died), I could feel it push a bit more on the brakes.
Now, that is a very large cam with a huge lope. On a smaller cam such as yours the lope is going to be closer together which would cause it to seem as it was pushing through the brakes the entire time.
My GFs TA did this and she just had an ls6 cam. We put a TCI 3200 converter in it and it idled like stock, no pushing through the brakes or anything of the sort. Hers was almost a PITA just sitting at a red light because you had to hold the brakes so tight.
In my car (226/228 .588 114 w/ PTC 4000) I can let go of my brakes and the car BARELY BARELY creeps forward, a slight incline and it will sit there or sometimes roll back.
That isn't really an answer or an explanation of why it is doing what it is doing... But the only thing I can think of as for what is causing it. It could be spot on or totally out in left field somewhere with the lights turned off.
The cam is surging. Basically the same thing that happens when you run too low of a gear and the converter locks at say 35mph with a big cam.
I'm going to guess it isn't pushing through the entire time? Or at least more noticeable when on the hit of the cam? That is just an assumption.
Before I got my white car dyno tuned (ms4 cam) it would surge at red lights and almost die at times. When the cam hit (especially when it almost died), I could feel it push a bit more on the brakes.
Now, that is a very large cam with a huge lope. On a smaller cam such as yours the lope is going to be closer together which would cause it to seem as it was pushing through the brakes the entire time.
My GFs TA did this and she just had an ls6 cam. We put a TCI 3200 converter in it and it idled like stock, no pushing through the brakes or anything of the sort. Hers was almost a PITA just sitting at a red light because you had to hold the brakes so tight.
In my car (226/228 .588 114 w/ PTC 4000) I can let go of my brakes and the car BARELY BARELY creeps forward, a slight incline and it will sit there or sometimes roll back.
That isn't really an answer or an explanation of why it is doing what it is doing... But the only thing I can think of as for what is causing it. It could be spot on or totally out in left field somewhere with the lights turned off.
06-27-2010, 02:49 AM
#42
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Since I do not know why it does it I am going to make the guesstimation that it is because the bigger cam is making so much more power the car wants to take off llike a rocket ship 
06-27-2010, 07:46 AM
#45
Yup, wasn't mentioned but I have a tranny cooler installed.
Reduced vacuum to my brake booster doesn't make sense for my issue. It is not that the brakes are weaker than usual it is that the car is pulling forward so hard. When I let off the brakes the car accelerates much harder than it should without me pressing in the gas.
Reduced vacuum to my brake booster doesn't make sense for my issue. It is not that the brakes are weaker than usual it is that the car is pulling forward so hard. When I let off the brakes the car accelerates much harder than it should without me pressing in the gas.
it looks like people are still telling you its the low vac. as well.. it seems like you dont want to belive you have two issues here
#1 is the low eng. vacume from the cam (normal but one of the side effects) that makes your booster less effective
#2 You need a stall
now if you were to down shift the car while slowing down and created higher vacume I bet you would be fine the first or second time you hit the brakes..
some people use vac. cans to store extra vacume (usually works best on manual trans cars)
vac. pumps... (heck some of the newer trucks come with these vacume pumps)
or real old school and diesel used hydro boost which rus off the powersteering pump (I think this works great but adds weight and robs power)
What I did on my last eng.. I went with a manual trans and lived with the brakes which weren't so bad after that.
with that being sad I think your best bet is to get the higher stall and be done with it. and finish this thread
06-28-2010, 02:15 PM
#47
it looks like people are still telling you its the low vac. As well.. It seems like you dont want to belive you have two issues here
#1 is the low eng. Vacume from the cam (normal but one of the side effects) that makes your booster less effective
#2 you need a stall
now if you were to down shift the car while slowing down and created higher vacume i bet you would be fine the first or second time you hit the brakes..
Some people use vac. Cans to store extra vacume (usually works best on manual trans cars)
vac. Pumps... (heck some of the newer trucks come with these vacume pumps)
or real old school and diesel used hydro boost which rus off the powersteering pump (i think this works great but adds weight and robs power)
what i did on my last eng.. I went with a manual trans and lived with the brakes which weren't so bad after that.
With that being sad i think your best bet is to get the higher stall and be done with it. And finish this thread
#1 is the low eng. Vacume from the cam (normal but one of the side effects) that makes your booster less effective
#2 you need a stall
now if you were to down shift the car while slowing down and created higher vacume i bet you would be fine the first or second time you hit the brakes..
Some people use vac. Cans to store extra vacume (usually works best on manual trans cars)
vac. Pumps... (heck some of the newer trucks come with these vacume pumps)
or real old school and diesel used hydro boost which rus off the powersteering pump (i think this works great but adds weight and robs power)
what i did on my last eng.. I went with a manual trans and lived with the brakes which weren't so bad after that.
With that being sad i think your best bet is to get the higher stall and be done with it. And finish this thread
08-02-2010, 08:36 PM
#48
Checked the Vac pressure and it is at 16 inhg in gear at idle. I guess it is pretty good since the 228R with a 114LSA has 0 overlap.
I hear what you guys are saying about not having as much vacuum so the brakes dont hold as well but it doesnt explain why the car wants to rocket forward when I let off the brakes? It pulls forward way harder than it should off idle.
Anyway I have a stall now which I am sure will fix that issue so I guess regardless of what is causing it a stall is how to fix it.
I hear what you guys are saying about not having as much vacuum so the brakes dont hold as well but it doesnt explain why the car wants to rocket forward when I let off the brakes? It pulls forward way harder than it should off idle.
Anyway I have a stall now which I am sure will fix that issue so I guess regardless of what is causing it a stall is how to fix it.
08-03-2010, 11:54 AM
#50
Hmm..
Your cam with its increased low end torgue and decreased vacuume over the stock cam is trying to surge and push through the brakes due to the stock stall, which is making feel like it wants to rocket forward. where as a larger stall essentally has the extra cushion room so that you don't feel it pushing or surging forward in the brakes at idle.
Pretty much the anwser everyone else gave you but I tried.
Your cam with its increased low end torgue and decreased vacuume over the stock cam is trying to surge and push through the brakes due to the stock stall, which is making feel like it wants to rocket forward. where as a larger stall essentally has the extra cushion room so that you don't feel it pushing or surging forward in the brakes at idle.
Pretty much the anwser everyone else gave you but I tried.
