D2 V8 brake servo and vacuum pressure

[alanbettison]

D2 V8 brake servo and vacuum pressure I placed this thread on the D2 section, but didn't get a solution so I thought I would try here

I have been advised the brake vacuum pressure should be 17 in of Hg

At the moment I am only pulling 14 - 15

Master cylinder has been changed and the brakes have had a abs pump bleed

Any advice please

thanks

[bee utey]

Brake vacuum will vary with:

idle speed
state of tune
altitude
accel/decel throttle position
leaks
faulty non-return valve

Many variables.

[alanbettison]

this straight from the plenum chambre and the engine has just been rebuilt

thanks for the advice

[bee utey]

this straight from the plenum chambre and the engine has just been rebuilt

thanks for the advice

So it's the manifold vacuum reading at idle that you are checking. Pressure is what you get after a turbo is fitted and you nail it.

Your motor may be a bit tight. Give it a few thousand and check again. If it doesn't improve try another vacuum gauge, or it may be the camshaft timing is slightly different to the stock cam. Do the brakes work OK? If so it is of little concern.

[alanbettison]

Its the brakes that has been the issue

Replaced the master cylinder and 2nd hand brake servo

Vacuum gauge a bit dodgy, to be replaced next week along with the one way valve

thank for the help