I just bought a great 1965 Plymouth Belvedere. The car ran great coming home on the highway. Then I needed to hit the brakes hard for a yellow light. After getting off the highway The car stops so-so, could be better. The problem is the engine starts smoking at the red light. Was like being on a cloud all this white smoke comes billowing out. However, while idling, the smoke stopped, and there was no smoke while taking off. Come to another light have to hit the brakes harder then normal. Cars smoking again at the red light. Pull away the white heavy smoke is gone. Get home revving the engine up no problem a little smoke on deceleration but nothing major. Car has power brakes. Could the power booster be leaking brake fluid into the intake manifold? Brake fluid in master cylinder seems full to the brim. Any ideas please someone.

It is possible for the master to leak into the power brake booster. Check fluid level to confirm.

If it is leaking you will need both the master and a new booster, the brake fluid eats the rubber diaphrams in the booster.

I had a Firebird that did this same thing it turned out that the #1 wrist pin was coming out of the piston and ate a trench in the side of the cylinder. When I hit the brakes hard the oil would slosh to the front of the motor and into the trench making a bunch of smoke. I did a compression test on the motor and it actually checked out OK the wrist pin was plugging the trench. I also had an Opel Gt that had a bad master cyl and booster that would do this also but the smoke was white not gray like oil. Take the vacuum line off the booster and plug it take it for a drive and slam on the brakes if you don't get smoke it's the master/booster. If it still smokes it's a motor problem.

Valve seals did pretty much the same thing for me. Some times it would run pretty clean and other times it was just embarrassing. I had 2 seals that were in pieces. I don't know it didn't smoke constantly.

i agree, unplug the hose to the booster, and put a bolt in it so you don't have a vacuum leak that runs half your engine lean and burns your exhaust valves (DAMHIK!)

take it for a drive, but be careful, your pedal will be ROCK HARD! so be ready for some pedal effort, and leave some space between you and the guy in front!