Eddie & the Cruisers

Anyone added a vacuum pump to assist vacuum to the power booster?

Since I installed the LT4 Hot Cam, my vacuum from the intake to the booster varies between 12 and 15 psi at idle. Too low to supply enough vacuum for the power brakes. I installed another power booster and still have the same results...not enough vacuum. Wasted $180.00. Runs good but now feel/see a drop of about 100 rpms at idle from time to time in park and in gear.

Tuned by pcmforless. Installed Bosch III injectors and Bryan says the data scan shows it is on the money.

Mojave

Hotcam really shouldn't reduce vacuum so that it won't work the brakes, it isn't nearly that radical. I had a Hotcam in my car and it did not cause this. I suspected something is up, perhaps a bad booster or crack in the vacuum hose to the booster.

PDQUIK95

As stated above, 12 to 13 lbs. should be sufficient to operate the power brake booster. You may have a vacuum leak somewhere else in the line. A Hot cam is not that much cam for the engine. I run 12 lbs. of vacuum at the manifold with no power brake problems.

jmeyer58

Another suggestion is to put a new checkvalve in the line so that the booster will have the vacuum from when the car was off idle. Yours may not be hoding the vacuum.

Churchkey

As suggested change the check valve & also replace the hose to the check valve. Booster hoses deteriorate from the inside out.

MarkBychowski

Agree with the above statements. I used to have a hotcam and absolutely no problem with vacuum / brakes. My new engine has a much larger cam and still no vacuum / brake problems.

Check your vacuum lines and check valve and you should be fine unless the booster just happened to crap out at the same time.

Eddie & the Cruisers

Before the cam install, the old booster, check valve and new brake pads were fine...no problem at all for 2 years.

Since the cam install 6 months ago when the problem started, I finally installed a new booster, new check valve and new hose to the intake port fitting just yesterday and have the same results. It seems that neither booster (old or new) has enough volume of vacuum to assist the brakes. I have checked all the vacuum lines that I could find and all seem to be OK.

rodj

One alternative

http://store.summitracing.com/partde...5&autoview=sku

Ultimate solution
http://hydratechbraking.com/products/c4vette/

Mojave

This is a bit of a reach, but perhaps the cam timing is off or maybe what you installed wasn't really a Hotcam. My car has a cam much, much bigger than a Hotcam and it has plenty of vacuum.

There has to be something else going on here.

Eddie & the Cruisers

Thanks, rodj, I am leaning toward a cannister addition.

Eddie & the Cruisers

Don't know what you are referring to stating perhaps it 'wasn't really a Hot Cam.' It is the GM LT4 Hot Cam kit w/ 1.6 rr's, HD springs and new HD roller lifters, ported heads and headers. Beats the h*ll out of a stock LT1 cam.

The timing is right on, no knocks on pump 93 octane gas, can break the 11" tires loose at 40-45 mph at WOT on the street....can't get the 11" tires to hook up on the track at WOT and will continue loose down the tract almost to the finish (1/8 mi track) and its a convertible (200# heavier than a coupe and I weigh 250).

I don't need a monster cam as some people do. If you can't be helpful, go peddle your sarcasm some where else.

QuikZilver

I run a canister on my 86 Monte Carlo SS. The cam in that car isn't too radical, either, but braking was like pressing against a brick wall. Installed the canister and now I don't have a problem.

Eddie & the Cruisers

Thanks for your input. That is exactly what I'm experiencing.
I will be looking at one and a place to mount it.

jfb

Don't you mean 12 to 15 inches of mercury pressure? 12 to 15 psi isn't right!

Fastmax32168

I dont read anything sarcastic in that guys origonal post. I think he was trying to be genuinely helpful. Lots of stuff gets peddled nowadays as something that its not.
Roy

Da Mail Man

.....here is the first page of a thread that was started a while back..somewhere in it i discussed making a "test" vacuum reservoir for those with radical cams and low vacuum...

....the test unit would only cost les then $10 and would/could have saved you some bucks...lot of good info in the thread so, i would read it if you care to...

http://forums.corvetteforum.com/c4-t...n-finally.html

larry00

My custom Comp Cam runs as low as 11 lbs at idle and no brake booster problem.
I understand if you have 10 lbs or better you are OK !

Mojave

<helpful response>I wasn't sure if you got the cam used, in which case there was a chance it wasn't a Hotcam. Also, my point in mentioning the cam size of my car is that my brakes work just fine. I'm 100% sure your cam isn't causing your brake booster problems.</helpful response>


<sarcasm on> Once you add your vacuum canister and it doesn't fix your problem, you can come tell I'm right. <sarcasm off>

Eddie & the Cruisers

Yes, I should have said 'inches of vacuum'.

You are right, just got tired of suggestions to check the hoses, replace the check valve, replace the booster, might not be a Hot Cam, might be out of time, etc., etc. Those are the first things any half-mechanically knowledgeable person would check or replace and were addressed in my first 2 posts.

Sorry, Mojave, I had just experienced a troubling family situation that had happened and should not have been posting. Actually, and as I notice, happened in your area, so I guess you were lucky and I picked you to take out my frustrations. Sorry again.
Could cost my GS graduation in 4 months, or the job offer after graduation. Dumb, stupid, wasn't raised that way. What can I say? 21 year old College grownups with a bright future. Thanks for your input.

Just a thought.
How many times do you post or read a post and see that a responder either doesn't read all of the post or reads the title and immediately starts diagnosing the problem using all the things the original poster stated he did or tried with no success.
Just a thought.

rodj

But the problem is we get a lot of people post up a problem and they haven't even done basic inspection first, let alone the obvious stuff.

Check the "my car won't start" posts.
Most run something like ;
"I turned the key and it won't start; what is the problem?"