My 71 RR came equiped with 4 wheel manual drums. Although it stops OK, (and by that I mean sorta poor) I was considering adding a power brake booster. I know the way to go would be to do the disc conversion up front and all, but I wanted to leave it all somewhat original. The engine sports a Purple Shaft 284 duration and 484 lift cam. Would I have a vacuum problem and would I really gain anything by adding the booster? I'm sure I would also need the proportioning valve, and I assume I would also need to change my master cylinder. Finally, if I add the booster, could I use the original plate that bolts my manual master cylinder to the firewall, or do I need a new one of those also? Thanks.

My 71 Roadrunner has power drum brakes and I am running the purple cam 474 lift. You need to check what vacuum you are running as I am, running about 7-8 inches at idle. I works just fine as the engine builds up more vacuum when cruising around town. I had to replace my booster check valve to hold the vacuum when builtup. If you are running much lower that that, you might want to rethink the booster idea. See attached pic, I think the master cylinder is the same.
Ron

Waste of time and money. Drum brakes have too many inherent problems, and poor capacity to stop, especially repeatedly and high speed. They get hot and glaze. A power booster will make them easier to push, but when they exceed their capacity to work, all the brake pressure you can put on them will not make the car stop ! Your money and effory would be much better spent on a manual disc conversion Original is nice, but a car always looks bad with the front end smashed from a couldn't stop !

Thanks guys. Perhaps a rethink of doing a disc swap on the front end is in order. Would I use the same Master Cylinder, I'm guessing not? Can I retain my 15x7 Ralleys?
Thanks

If drum brakes are in good shape they will stop your car just fine from 80MPH down just as well as discs will for 1 or 2 times. If you hit them above 80MPH or so (especially more than once) the discs will outperform them.
My last two factory Hemi cars have had the standard 11 inch drums and both cars have stopped great, my 66 is non-power and it does not need to be upgraded. I do not drive on an interstate in heavy traffic above 70 MPH though. It really depends on vehicle usage.

Sheldon

I converted my Challenger from manual drums to manual discs (the magazine conversion using junk yard parts) and NEVER looked back. It seemed like the stopping distance was cut in half.

I have power front discs on the GTX. It seems to me there's less "feel" when I stop and they don't actually relieve much in the way of pedal effort. I also don't like the way the booster takes up so much space in the engine compartment.

If it were me, I'd spend a day in the jy and another browsing through the autoparts stores and convert to manual front discs.

How's about the master cylinder and wheels question guys? Do they need to be changed if I got to a manual disc set up in front? Thanks.
Nice engine compartment BTW Ronn.

you're wheels are fine & you should ch to a MC with the larger disc reservoir(the rear most one) though people have kept the orig drum MC which has less fluid capacity & had no problems & if doing that check the rear most port with a drill bit & see if it there's a spring loaded residual pressure valve in there,if so pull the brass seat & remove it.

Thanks Robert. Perhaps I can get away with the M/C I have now. It's been on for only 3 years or so.