How much vacuum is needed to operate the stock brake booster. I have a 347 with a lopey cam.
I am measuring 10" of vacuum. Is this not enough vacuum to operate the booster correctly??
Don't Know what cam is in it because I bought a crate engine and the builder does not disclose the cam specs. The pedal is stiff and high. The booster is new. tried adjusting the push rod length but NG.
Is there anything I can do to assist the booster??
You can try a vacuum canister, and if all else fails i've seen rather inexpensive electric vacuum pumps. Are you class racing or something why wont your engine builder give you cam spec's? How the hell are you supposed to get a base line tune or torque converter w/ out cam specs?
I'm not class racing. I told the builder my set up and built the 347 engine to 373 gears manual T5.. The idea of a vacuum canister is to hold more capacity of vacuum?
I have done more investigating on the symtons---- The first push on the pedal feels like the booster works and the car stops good. but each additional push the pedal gets harder. Is the booster running out of vacuum?? When the car is under load the brakes are ok until I push the clutch and the engine comes down to idle then the pedal is hard again. This is a PITA!
what kinda engine builder doesnt give out the cam specs, maybe try adjusting ignition timming to see if you can find a little more vac, I thnk 12 and up would be good
"What kind of builder does not provide a cam profile ?"
If you're still fuel injected... knowing your valve timing is critical to tuning.
Despite this... lets' go with the the theory that the builder has a magical cam setup which cannot be broached to the tuners and owner.. They, in the least, should be able to suggest what your vacuum should be.
I've been in situations where I had a lot of overlap and the cam could not build vacuum for accessories. I went with a canister which provides a small reserve. Suffice to say that you'll never road race with this setup and if you're stuck in traffic, your brakes are more likely to feel manual than power.
There are expensive and heavy unit solutions where you can install an electrical vacuum pump. I say heavy because when I last looked it was a fairly stout looking accessory (moroso ?).
Another solution might be to consider a late model mustang brake system.. which finds it's power through the power steering pump, rather than relying upon vacuum. I had thought about this for my 1992 ...and I may return to the idea. Bigger fish to fry at this time.