I wrecked my 9 Bolt 1988 formula 350 unfortunetly, and i bought a 1989 formula 350 - but it has a 10 bolt drum brake rear end on it. I was wondering how hard it would be to switch the BW 9 Bolt onto the 1989 and what parts from my 1988 would i need to make the switch.

 

rear end, and for optimal braking performance, the master cylinder and combo valve

 

you have to change to prop and master, mostly cause drum brakes use a residual check valve which holds pressure in the rear brakes to help over come spring force to decrease lag time of the rear brake application
the rear disks will drag and wear out very fast if this is not removed
it also have another valve that slows down the application of the front brakes so the front disks and rear drums come on at the same time,

 

if you say so, yet third gen guys have been running LT1 rear brakes for years with the original DRUM MC and PV ,
there is no residual valve, however, the pressure to the rears is delayed on apply

 

pressure to the front is delayed, rears have lag time because of spring force, all drum brakes hold a small amount pressure to keep pressure on the wheel cylinder seals, other wise they will pull in air and leak,
its alos to cut down in lag time to help over come spring force

 

not saying you have to change it, but draging rear brakes would effect gas millage and burn up brakes and rotors

I'm running a disk prop and master with a drum rear,(blew my disk rear, got a temp drum until I finish rebuilding the disk)
my brakes suck until I pump them up because of it,
and I got to bleed my rear brakes on a some what regular basis

 

Been there and done it: Only items needed for the change and the 9-bolt Proportioning valve and the parking brake cables onther then that it is a straight forward swap. You also may need flare some fittings.

 

ok so mostly i need:

the rear end assembly
proportioning valve
master cylinder
and parking cables

i dont like the drum rear, plus its a 10 bolt as opposed to a 9 bolt BW i have just sitting around.

 

Might check ratios before getting into this deeper. My 89 with the 9 bolt had a 2:77 rear while the 88 with drum rears has a 3:23, and that is quite a difference in performance.

 

Forget replacing the Master Cylinder, not neccessary. Been using my original Drum one for years now with no problems.

 

well ill test it on the road and see which one has more pull to it but i come out of 3rd at 125MPH in the 1988, im pretty sure it will be the 3.27....the 1989 has some slicks on it right now - and i know it pulls hard, not sure what gearing yet on the 1989, maybe 3.73?