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'66 big car disc brake conversion
Who here has converted from drums to power front discs on a '66? Did you use later year GM parts, or is there a conversion on the market that I can't seem to find? The car is a Bonneville.
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One of the members in this forum, Scarebird, probably has a bracket set up and a parts list to convert your car to front discs. There is also Master Power Brakes (MPP) who I used several years ago to put front disc brakes on my '64 Grand Prix.
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It's possible to use the disk brakes from a 1968-1970 full size Pontiac, but those parts weren't very common even when new and are hard to find these days. The Scarebird kit will work with the original 14" wheels, the Master Power kit requires 15" wheels.
https://scarebird.com/index.php?rout...product_id=251 https://www.mpbrakes.com/front-brake...1966-front.asp |
66 disc brake conversion
Steve
I found a few sets of 69-70 full size disc brake setups years ago in local salvage yards, using one now on my 66 Catalina. The steering knuckles are a bolt in system, and I used the brake calipers as cores for rebuilt ones. An hour glass beading the knuckles and brackets and sprayed with a rattle can, they look new. The rotors on both sets were usable, well above minimum thickness for machining, but I doubt they could be turned again. I figure that with the 2-3,000 miles I drive it every year, they should last me a lifetime. I used the original 1970 power booster, but bought a new master cylinder and flex hoses. I had to switch over to 15" wheels for clearance on the brake calipers. I've heard good things about the Scarebird conversion, but these were local and inexpensive. Ron |
Scarebird is the best bang for the buck.
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Here is a pic of the Scarebird conversion I performed on my ‘66 2+2.
https://uploads.tapatalk-cdn.com/202...8213d77dd9.jpg https://uploads.tapatalk-cdn.com/202...5250df1d8c.jpg Sent from my iPhone using Tapatalk |
Thanks for the pictures. Is that an aftermarket upper control arm you have there? Sorry if this has already been discussed.
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But the bleeder on the rear caliper picture is facing down. Aren't they supposed to be at the top of the caliper?
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Yes, the upper control arms are from RAM Air Restoration I believe. They are suspension corrected and have a taller than stock ball joint on top. The lower arms are stock with polyurethane bushings, 1 1/8” aftermarket sway bar with poly bushings, and Lares fast-ratio manual steering gear. KYB shocks all around. Sent from my iPhone using Tapatalk |
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Yes, this was an early pic as I was dry-fitting everything. I switched the calipers during final assembly so the bleeders are up. Regarding Scarebird rear disks, I will say that I have heard a couple people mention the rotors not being centered in the rear caliper and having to shave one of the pads to prevent rubbing. I ran into this as well, but only on one side. I believe the issue is that where the rotor lands inside the caliper has a lot to do with where the axle bearing ends up when it is pressed onto the axle. I believe the people that have had issues have axle bearing(s) that aren’t pressed onto the axle quite as far as others. This leads to an axle flange that sits out slightly farther and hence the disk brake rotor and wheel sit farther out as well. In my case I could not mount the caliper with pads into place due to the outer pad being against the outer rotor surface. Next time I have the car in the air I’m going to pull the rear axles and test out my hypothesis. I also have noticed that different brands of pads seem to have different thicknesses of friction surface. The first set I received which was a high-quality off brand, was fine on one side and tight on the other. The second set of ACDelco were much thicker and wouldn’t work on either side. Fun times. :-) Sent from my iPhone using Tapatalk |
Ben - thanks for the feedback - we did NOT know this concerning the axle bearing.
We are however aware of the pad thickness issue - some calipers loaded won't fit on the rotor period, which make you wonder how they sell them. :mad: If you have more pix we would like to see/use them. Did the Wilwood's clear the stock 14" wheels? |
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Yes, I couldn’t believe how much thicker the AC Delco pads were that I received. I still have the pads so I’ll try to dig them out and take a comparison pic. Definitely not consistent. I did not try the OE 14” steel wheels with the GTO-replacement Wilwood front calipers since I already had 17” on the car. I sold the original steel wheels so I don’t have a spare to try them now either unfortunately. I do have many detailed pics from the front / rear conversion and all of the part numbers I used for the braided stainless brake lines if you want additional info for your customers. Everything went together pretty well, but I would definitely make my own brake lines next time rather than buying the kit from Inline Tube for this conversion. I had to modify a few so I could have done it cheaper myself in the end. As far as getting the front dual piston Wilwood calipers to fit is concerned, they bolted right up, but there is a small clearance issue due to the wider dual caliper body. I didn’t realize this until I tried to mount the calipers over the rotors and couldn’t get the calipers to move outward far enough. I had to clearance your mounting bracket slightly to allow the caliper body to slide freely in the bracket. See pics below. I can send you more detailed pics directly if you like and will have the car on jack stands shortly since they just salted the roads here in Illinois. I put on a couple thousand miles this summer and they brakes feel really good and are well-balanced after bedding in the pads according to the instructions provided with the Wilwood calipers. I performed an OE manual to power brakes conversion to this car at the same time I did the disk conversion so that was an interesting research exercise as well. https://uploads.tapatalk-cdn.com/202...917ebc88a8.jpg https://uploads.tapatalk-cdn.com/202...3c446999d6.jpg https://uploads.tapatalk-cdn.com/202...397031b2ab.jpg https://uploads.tapatalk-cdn.com/202...1312667717.jpg https://uploads.tapatalk-cdn.com/202...4acfffb9bf.jpg https://uploads.tapatalk-cdn.com/202...c2159fb289.jpg https://uploads.tapatalk-cdn.com/202...4bd50fc726.jpg Sent from my iPhone using Tapatalk |
Ben - excellent work; we will mod the next batch to clear this - even though Wilwood is a competitor having the ability to use their "upgrade" calipers would not hurt.
I am concerned about the size of the booster; if that is a dual 7" it may not work so hot with a low vacuum motor. |
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One other modification I had to make that I didn’t take a picture of is to the inside of the Wilwood Calipers. When mounted, the outside edges of the brake rotor would slightly contact the inside of the caliper when rotating it. There was plenty of meat inside the caliper so I used a small file to create about 1/16 inch of clearance for the rotor edges. The power brake / disk master cylinder conversion kit I used has the following specs from the MP site: 1966 Pontiac Catalina Power Brake Conversion Kit - 9" Dual Diaphragm Booster w/OE Manual Brakes 9 inch Dual Diaphragm Brake Booster 1 inch or 1-1/8 inch Bore Master Cylinder Powdercoated Black Booster with Black Master Cylinder For Use on Cars with Originally Equipped with Manual Brakes The kit worked ok, but I one thing I didn’t immediately realize is that when buying the kit for a ‘66 Catalina with OE manual brakes, the back of the booster has a large bracket on it to change the manual pedal ratio to a less aggressive power ratio. Since a factory booster in my car looks a lot cleaner when mounted directly to the firewall, I removed the bracket and remounted the crevice to the booster. I then had to source a power brake pedal for a manual shift car which is pretty impossible for a full size, so I made my own by welding a manual lower section (small foot pedal since there are three) with the longer upper section from a power brake pedal assembly from an automatic transmission car I bought of eBay for $20.ot was a bunch of extra work, but it looks a lot nicer imo. Sent from my iPhone using Tapatalk |
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Very nice work Ben! Not sure I saw it, but what hub and rotor did you use on the front? Any part numbers for your setup would be great to have as I plan to do similar to my 66.
Rotors, calipers and so on. Thanks! |
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I have a write up I put together for another group with part numbers for everything I can send you / post here. I’m away from home for a few days so i’ll have to check my PC when I get home. I believe the front rotors are originally made to fit a 2006 era Dodge Sprinter 3500 van with OE 16” wheels. The info I’ll provide says specifically. Sent from my iPhone using Tapatalk |
Just wanted to follow up on something SB mentioned above, about the extent to which a booster will work in a low vac environment. I've been looking at the unit Ben used (from MP) and their website notes that 18" is needed. 18" seems like a lot. Does anyone have any experience with this booster in use? Thanks!
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The reason I'm asking is because the single MC in my Bonneville (on a bendix booster) is leaking. Plus, my power brakes are not working that well with my cam. Anyway, I'm at a bit of a crossroads and am wondering if the MP unit might solve both of my problems.
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I’ve been driving all summer with it, so yes. The brakes seem fine. I checked my vacuum before I bought it and I’m just under 18 at idle on my ‘66 421. I will probably have to use a vacuum pump once i change cams I assume. Sent from my iPhone using Tapatalk |
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