Power booser question

[rrTor-Red]

Car is a 71 B and came with HD Power drums.

Will the drum booster work if I switch to discs in front, just change the M/C? Is there a difference in the two? Difference in linkage from the pedal? Originally came with a Midland Ross.

Thanks

 

[Propwash]

rrTor-Red

A Power booster for a drum set up has a different power assist ratio than a disc/drum booster. You should change to the appropriate booster. You will need a proportioning valve as well. Either buy a factory prop valve or plumb in an adjustable to the rear brake lines while retaining the distribution block already in the car. Your Master will definitely need to be for a disc/drum combo. Mostly because the drum/drum either don't have a residual valve built into the rear wheels port of the M/C or it's fluid function is different because of a different orifice size. Not positive on the '71 linkage hook up, but '70 and prior have an identical linkage between the power drum/drum and power disc/drum set ups.

Rock auto sells a OEM style power booster/Master combo for your car.....

 

[rrTor-Red]

Thanks Will for the reply. Yeah, I looked at Rock Auto and others as they list them. My booster right now looks identical but wasnt sure about the inside stuuf if that was the same. I already know about the M/C. Now, need to find out the linkage diff, if any, between the two.

 

[Propwash]

Hey no sweat man..Wish I could help out more, but I only have Factory Service manuals running up to 1970. Best of luck to you.



Little update...researching that linkage rrtor-red, the linkage is the same between power drum and power disc/drum for '71

 

[RustyRatRod]

I used to be a power booser in high school.

 

[5.7 hemi]

Just askin' cause I'm not sure.......aren't boosters the same and only needing to change the master??? Seems as though that would be the only requirement when switching from power drums to power disc's.

 

[Propwash]

Good question 5.7.......Couple differences between the two. First would be the difference in power assist ratio. Second would be the disc/drum boosters from our dinosaur cars are dual internal diaphragm. Drum/Drum are typically Single. Obviously that design feature creates different results. Real simple way to think about it is; Mopar back in the day had different boosters for disc/drum cars than drum/drum cars and for a reason. If one's switching to disc's up front, best bet would be to replicate a similar scenario as factory. Seen a few folks use a drum booster in a disc/drum combo with satisfactory results, but not optimum results. Without a doubt the master needs to go

 

[5.7 hemi]

Ok, now I'm on the same page. Thanks Propwash, I learned some useful info.

 

[Propwash]

:icon_thumright: Hey no problem 5.7..I'm no pro by any means, but sure learned a lot myself before doing the past couple conversions. Talking with folks like The Ramman and aftermarket manufacturers sure was enlightening. A lot of great books and articles on it as well...There is one in particular at Moparts I wish I could remember where it was. Sure would make a good sticky note

 

[rrTor-Red]

:icon_ A lot of great books and articles on it as well...There is one in particular at Moparts I wish I could remember where it was. Sure would make a good sticky note

Are you talking about the book by Andy Finkbiner(?) (Sorry if I mispelled the last name)

 

[Propwash]

Are you talking about the book by Andy Finkbiner(?) (Sorry if I mispelled the last name)

No, but I do know who you're talking about. Owner of AR Engineering and pretty smart fella when it comes to mopars.
Here's a nice little write up from him:

http://arengineering.com/tech/mopar-musclecar-brake-upgrade/