Am I nuts? My poor Impala

[USSkoval]

First, a little background. I have a '69 Impala four door hardtop that was my first car. I drove the wheels off the thing the first few years I had it, then I started acquiring more cars and it got driven less and less. Now it's to the point where it only gets driven a couple times a year because there's usually something wrong with it from too much sitting. Last year a rear brake line blew and I've never even had the rear drums off yet, so the shoes are likely well worn out. The fronts are also drums and are non-power.
Now here's where it gets a little interesting. I just picked up a rear disc setup for free from '00-ish 4x4 s10 blazer that should bolt up to the rear flanges of the '69 10bolt housing. Yes, that's right, I would like to add rear disc brakes to a car with front drums
I know it sounds silly, but is this a bad idea? My way of thinking is that doing ANYTHING to this car is better than nothing... and it would be free! Maybe if I get working on the car again, it will get the ball rolling on fixing up the rest of the car.
Thoughts?

 

[chevy wrangler]

so that axle is a bolt-on??
my uncles '69 impala 2 door hard top has disc brakes front and drums rear with a 12bolt

 

[Goose]

You're asking for rear wheel lockup, which is one of the easiest ways to spin and crash.

On typical front disc, rear drum the proportioning valve is set up to get fluid to the rear and before the front. Drum brakes take longer to engage once fluid is moving because the brake shoe sits farther off the drum than a brake pad sits from a disc. This is due to the nature of the design. So, you get fluid to the rear first to make up the difference in time in order to have even braking.

Now, if memory serves, drum front and rear has no proportioning valve. At least on my old Kaiser M715 with drums all the way it had none.

So, you put disc on rear and still drum on front of your impala. Suddenly the rears work sooner than the fronts and you get rear brakes before fronts. Kinda like standing on the e-brake every time you stop.

See the problem?

 

[pauly383]

Go by front caliper brackets , which is the most exotic part you need to buy . Cut the upper bolt boss down some so the caliper brackets sit flush on the drum spindle .

Parts store booster , master , hubs with rotors , and calipers .

Find prop valve on something same size .

Cheapest front disc conversion there is ( assuming the B car is laid out like a A/F car which you can do this on ) .

 

[USSkoval]

Unfortunately, this swap will never happen anyway I found this out after beating the drums off the rear and pulling one axle. Apparently the backing plate flange on a 8.2 10bolt is larger than the flange on the later 8.5 10bolt used in the f-body (that this swap has been done on). I always thought they were the same I could drill new holes no problem, but the caliper would not be anywhere close to being centered on the rotor. Crap.
I did confirm that I have a crappy 2.73 ratio though, so that explains the sluggish performance even after all the work I've done to it.

 

[Mike D]

The 69 Chevy Chevelles (malibu) were going high performance at that time. You might be able to swap out your drum brakes for chevelle power front discs, brake booster and master cyclinder. If my memory serves me any Impala from 66-70 with a 396 engine came factory with front power disc brakes. I had a 68 Impala with 327 4 speed, it had power drum brakes. They worked real good except if water got into the drum ( deep puddle ). Why not just put a booster and and new power brake master cylinder. That would be the cheapest way to go. They should just bolt up. I believe even the brake peddle rod is the same. If you take the last option, Replace the two rear wheel cylinders. Make sure they are for a power brake system. One thing most people don't concider is that on a rear wheel drive vehicle the engine slows up the rear wheels more than the rear brakes.

 

[pauly383]

Good luck finding a cheap set . I would think nearly all the old cars in Ohio are crushed , or the people in the yards are hip to it and pulled em all already .

I can't even find factory 68-72 brakes in rust free AZ for a song anymore , just too popular .

Thats why buying the caliper brackets only repopped makes sense , the rotors , calipers , booster , and master are stocked at parts store generically , and by grinding the drum brake spindle bolt boss 3/4 of an inch you get discs on drum spindles , and you reuse your hubs and bearings .

 

[USSkoval]

Yeah, the drum fronts need to go, the lack of power assist soesn't bother me much. The drums do stop pretty well, but only for about 30mph of scrub- not good if you're going 65mph or better. I plan on ponying up the money for a front power disc kit because I woulde also like to go with 2inch drop spindles at the same time. For the rear, I may be able to make some caliper mounts to use the blazer parts I got for free.