skydude

Chevelle 5.3 swap. I know there is one vacuum source at the back of the Vortec intake but looking for two. Like to have a backup for the brakes. Anyone know if there are two available on the truck engines?

Ls1.63cad

There should be one on passenger side will have the factory end cap that will have to cut off

Ls1.63cad

Here is a pic

ls1nova71

iTrader: (4)

Yes, you just break that little tab off and can put a hose on it. Its the vacuum source for the HVAC system in vans that don't have electric blend doors. My question though is, what year of Chevelle had vacuum wipers?

skydude

Ls Nova, before I started on the swap the wipers were not working and don't know why I thought they were vacuum because they are electric, but I would like to have a backup vacuum source for the brakes.

ls1nova71

iTrader: (4)

Ahh, gotcha. I didn't think they ever made a car that new with vacuum wipers. On a side note, that vacuum source on the side of the intake will run small vacuum operated devices, but will in no way be a backup source for your power brake booster.

Old Geezer

iTrader: (3)

My $.02.......Should the vac for the brakes fail, hooking a second line up won't be a "backup" source.
IE: The main hose falls off. The vac in the intake will drop, as the engine pulls air from the source of the lowest resistance to flow.
Therefore, the "backup" vac will drop, negating the value of the second system...

skydude

I wasn't planning on using two at once but I had heard a couple people say that in some cases the vacuum wasn't enough for the brake system so that's why I was asking about what sources were available. Thanks for the replys.

oldgoat69

Unless you have swapped to a very aggressive cam your engine vacuum should be sufficient for the brake booster. Most GM boosters will work with as low as 12 in hg. Most LS engines develop around 17 at idle. Unless you plan to add an electric vacuum pump a redundant source from the engine won't get you anything. The biggest thing to make sure of is that your source is direct intake and not metered or switched through a valve or switch.