Can't stop it....

[Sweeet Ride]

I recently switched out my 289 for a 408 and have been having trouble with brakes ever since. I have power discs on front and drums on rear as stock....they have always been very responsive and full brakes with the lightest touch 8until this engine change! front discs and calipers are next to new....2 year old master cylinder....
I think I have 2 separate problems (but maybe not)....
1...spongy pedal....not touchy and responsive like they were
2...even tho' the first pump of the brakes isn't great...the 2nd pump is almost non existant and the 3rd is not there at all....dangerous in city limits.
Seems like we're not makinfg enough vacuum off this engine....why would that be and how do I fix it?

 

[iskwezm]

Get a vacuum canister to store vacuum
View attachment 378317

 

[Rusty67]

Buy a vaccume gauge and check your setup at idle just to verify that this is your problem. I would be willing to bet it IS your problem but it is always a good idea to check stuff out before spending money.

 

[Sweeet Ride]

Where did you find that cannister in the picture you sent?

 

[iskwezm]

Where did you find that cannister in the picture you sent?

Summit or Jegs.Look for Vacuum resevior.

http://store.summitracing.com/egnsearch.asp?Ntk=KeywordSearch&DDS=1&Ntt=vacuum+resevior&searchinresults=false&N=+115

 

[70vert]

Hydraboost or electric vacuum pump?

How about a Hydraboost (Hydroboost?) system if you have PS on the car? I may be talking out of the wrong orifice (sometimes when I sit down my voice sounds muffled, so maybe, lol) but are you guaranteed that the vacuum reservoir will always be full? I would hate to have any unpredictability in braking performance.

I was planning on putting in a Hydraboost or Electric Vacuum Pump Kit in when I put in my 408 - see here for the SSBC kit:

http://www.stainlesssteelbrakes.com/brakeproducts/brakeaccessories/Accessories

although I would want a quiet electric kit - not sure how loud the SSBC unit is.

 

[Rusty67]

How about a Hydraboost (Hydroboost?) system if you have PS on the car? I may be talking out of the wrong orifice (sometimes when I sit down my voice sounds muffled, so maybe, lol) but are you guaranteed that the vacuum reservoir will always be full? I would hate to have any unpredictability in braking performance.

I was planning on putting in a Hydraboost or Electric Vacuum Pump Kit in when I put in my 408 - see here for the SSBC kit:

http://www.stainlesssteelbrakes.com/brakeproducts/brakeaccessories/Accessories

although I would want a quiet electric kit - not sure how loud the SSBC unit is.

Hydroboost would be the better option if you have PS already.

I say trouble shoot the existing system to at least find whats wrong with it right now that way you can properly asses an upgrade or repair path. It could be as simple as a leaking vaccume hose or stuck check valve.

 

[68RCodeConv]

The reason it is happening is because your current engine either has: (1) a massive vacuum leak, or (2) a much bigger cam than the previous engine.

You can fix (1) pretty easy. Fixing (2) requires replacing the cam with something with less overlap. Or get a vacuum reservoir. Or a vacuum pump specifically made for this purpose.

 

[truck90278]

A vacuum reservoir will only hold the same amount of vacuum as the engine will produce. It does provide a source for vacuum which will help. As said in other posts, get a vacuum gauge and check the vacuum. You ideally would want to have 17 inche of HG to operate the booster adequately. Run the engine at 2500 and see what your getting. It does definitly sound like your low on vacuum. vacuum pump will solve the problem with low vacuum