ckimble

I am looking at disk brake conversion kits for my 68 and looking for some feedback. Both of these kits have been recommended to me by friends. Just curious to get some feedback from others that may have used either of these kits.

First is from Performance Suspension Technologies

Second is from Summit

Lastly, this is probably a dumb question, but how do I tell if I need the power assist or the manual kit?

Thanks!

joe_padavano

Unless you have money to burn, just use this kit and spindles from Speedway Motors:

http://www.speedwaymotors.com/p/4618...Brake-Kit.html

Spindles: $125/pr
Brake kit: $240
Hoses: $20/pr

Total: $385

Note that you still need a disk brake master cylinder and proportioning valve.

If you don't care about complete correctness, a replacement M/C is $16 from Partsamerica:

http://www.partsamerica.com/productd...pe=230&PTSet=A

Since I assume you're not looking at the megadollar four piston calipers that were factory on the 68s, this M/C will work fine. If you want the correct looking M/C, you can get this one for $59:

http://cgi.ebay.com/ebaymotors/67-68...QQcmdZViewItem

The 68 cars used the in-line proportioning valve shown here for $85:

http://cgi.ebay.com/ebaymotors/67-69...QQcmdZViewItem

This mounted below the M/C and has the advantage of not requiring you to disturb the distribution block on the frame. If that's too pricey, you can substitute a 71-72 combo valve shown here for $55, but you'll need to do more plumbing:

http://cgi.ebay.com/ebaymotors/GM-Di...QQcmdZViewItem

Then there's the issue of the brake lines. If you use the 68-style proportioning valve, you only need to bend new lines from the rear outlet of the M/C to the prop valve to the distribution block. Take off the one old line and cut, bend and reflare the ends to plumb the prop valve, or bend up two new shorter ones to replace it. If you go with the combo valve you may need to replace or rebend all the lines. In any case the flare nuts going to the M/C may have different thread and you'll either need adapters (available at most auto parts stores) or get the right flare nuts and reflare the ends of the tubes when you replace them.

Finally, there's the issue of the frame brackets for the rubber hoses to the front wheels. If you want to do this on the cheap, you can file the holes in the current brackets, but the easy way is to just buy these for $25:

http://cgi.ebay.com/ebaymotors/69-70...QQcmdZViewItem

OK, so what's the total?

$385 from Speedway, $16 for the M/C, $55 for the combo valve, and $25 for the brackets gets you disk brakes for $481. If you want the correct M/C and prop valve, its $554. Either way, this is substantially less expensive than the complete kits, at the cost of some extra ordering time for you. If you like to scrounge, you can find parts even cheaper on ebay or at swap meets.

As for the power vs. manual, it's up to you. If the car is power drums now and you want to keep the power, get a power disk M/C. It bolts to your existing power booster. If you have manual now and want to keep manual disks, get a manual M/C. If you have manual and want power, you'll need a brake booster in addition to everything above. It does appear that the Summit kit includes the power booster, but why pay for that if you don't need it?

ckimble

Great information! Thank you very much for the reply. Time to go add some parts to the shopping cart...

tclaemont

I presume you are converting froms drums to disks? The reason I ask is because it is common for owners to replace the original four piston calipers with newer single piston calipers. This is a straighforward swap with nowhere near as many changes that need to be made.

ckimble

Joe was right on... Looking to get rid of the drums for the discs. I went ahead and ordered the individual components and his advice saved me a bunch of money.

Joe, if we ever meet, the beer's are on me

Thanks,

Craig

bigbrother

Does this kit work with a 69 cutlass with the 14" wheels?
Thanks BB

MLKZDK

Hey Joe, my name is Fabio, I’ve been reading your posts, thank you for your time and dedication to keeping this information alive!

Well, hopefully you can help
me out here.

Do you know if the ‘68 442 was ever offered with factory manual disc front brakes as an option for non-W30 4 speed manual builds? Or if you could get them installed at a dealership after purchase if one so desired?

I have an OEM specs and production numbers booklet by James Kryta that says front and rear drums were standard in 68 and options were only power disc front, drum rear; Or power drums. Option code J52 and J50 respectively.

I believe I read in one of your comments that 4 speed manuals didn’t have the vacuum necessary for power brakes, so, by my calculations, that means they we’re not able to be optioned with front discs, unless they were W30.

(Seems like it was a package up-sell scheme to me)

Booklet says W30 packages with M21 received manual front discs.

My 68 442 4 speed manual convertible is in great condition, numbers matching and has factory manual drums all around.

I’m thinking of restoring a set of GM original 67-68 4 piston disc brakes for it, but would like to know if it was ever an option for non-W30 4 speed manuals, or if one could have a dealer install them after purchase.

My wheels are SSI non disc brakes, would need to source disc brake ones if to do the conversion. My car was built on the 5th week of May 1968. I remember reading something about disc wheel manufacturing issues in 68 as well…

Would rather not bother with GM discs and calipers if it would be better to keep the factory drums for show or resell purposes, in regards to period correctness for the options available at the time. It would be easier to get some updated calipers and discs and throw in the drums for those occasions, if that we’re the case…

I’m keeping the color the way it is for now, it’s a “plum iris” goes well with New Orleans, original was saffron.

Sorry this turned out to be a long post, but just a couple questions and an opinion I guess…

Thank you in advance!

joe_padavano

I don't know what booklet that is you're looking at is, but it isn't published by Oldsmobile. Be cautious of third-party books like that. There is not one piece of factory literature that talks about manual disc brakes with M21 for the 1968 model year.

In any case, you have a few things confused.

First, for the 1968-69 model years, all W30 cars came with the same 328/328 deg cam, no matter which trans you got. AT or MT, doesn't matter, the low engine vacuum was the same. It wasn't until the 1970 model year that the AT W30 motors started getting the same mild cam as did every other AT 442 that year. The 1970 MT W30s got the low-vacuum 328/328 cam.

Second, the four piston caliper disc brakes used in the 1967-68 model years were never offered in a manual option, period. The single piston caliper disc brakes first offered in the 1969 model year were available in a manual configuration on the 1969 W30 cars starting in mid-year.

As for the use of manual disc brakes on the 1968 cars, the Product Information Manual clearly shows that the only disc brake M/C installations were for power disc brakes. The only disc brake RPO codes were J52 for normal power disc brakes and J55 for the police package disc brakes (the difference was the linings). In both cases the part numbers for the pre-bent brake pipes from the M/C to the metering valve to the distribution block are the same. If there was an option not to use a power brake booster, the hard lines would be bent differently and have different part numbers.

One more thing. If you're really worried about being factory correct, you need to lose the Buick wheels.

MLKZDK

See that’s what I’m talkin’ about!
I had no idea those were Buick SSI!
The clarifying about the manual disc brakes year, golden, thank you!

Ok, cool, so that means to stay “factory correct”, as far as wheels and brakes; I would just need the correct design Olds SSI in 14x6, and to keep my drum brakes; Easy peasy! 😀

I was frying my brain over here. 😂

I guess, the “most factory correct” way to upgrade to discs for the 68 4 speeds would be the manual ‘69 GM single piston front disc brakes with the correct Olds SSI (disc brake version) wheels?

Was this a dealer installable upgrade for the ‘68 442 4 speed manual?

Oh, and, yes, the booklet is published by an enthusiast, it is second hand information. To be fair though, there’s a big disclaimer saying the information is right “to the best knowledge of the author” and to “keep an open mind”. 🙃

It looks to be sponsored by “Inline Tube” and “Motorcity Supercars”.

I’ve had her since last September, she came with another set of rims and tires on her, the FrankenWheels came as an extra set, fortunately! 😂 I think that may have been mentioned during the deal. I was recovering from covid at the time 🥴 , my head was scrambled eggs, so, I probably just forgot. 😂