HMMM... what could cause low vacuum?

[5.0Flareside]

hey guys, im trying to come up with all different reasons why low vacuum would be caused from stuff...

the reason i ask is, as most of yall know i tore the engine down for head gaskets and also installed a custom cam that was SD friendly (supposedly). Smog pump deleted and a few other things..

but i was having some issues yesterday when driving it to and from work. When i was slowing down to a stop when the truck would down shift sometimes my brakes would get soft until a certain point.. and it feels like its caused by low vacuum..


Any ideas..

 

[DNFXDLI]

Cracked or loose vacuum hose somewhere maybe?

 

[blacksnapon]

OK, ask yourself where does the vacuum come from anyway? Its essentially the piston going down, increasing the volume inside the cylinder, creating this "sucking". Competition, or otherwise performance camshafts have more than usual valve "overlap". Meaning, you still have valves open when they are usually closed in stock configuration. This lessens any available vacuum. Its one of the hazards of installing a "hotter" camshaft.

 

[LEB Ben]

Intake leak? booster leak? Loose vacuum tree? As dman said, cracked lines...sometimes they're so fine, the hose itself will look good, but if you start manipulating it, you'll see the dry rot.


Edit as Vince pointed out, how 'hot' is your cam? Could play a pretty big role in your lack of vacuum. If that does end up being the culprit, it shouldn't be to difficult to rig up a reserve.

 

[Bricks]

Are you running the same timing as you were with the stock cam?

 

[73F100Shortbed]

If you have no vacuum leaks then it is probably because of the cam like vince said. I'm sure summit racing has some vacuum reserve you can install.