Wilwood Disc Brakes for my 69 Firebird

[AM.MSCL]

The instructions talk about drilling the top original bolt hole and threads of the spindle. It talks about .578 which translates into a 37/64 size drill bit. Then tap it to a 5/8-18.
I was wondering if anyone had used a 9/16 = .5625 to drill it out and then tap the 5/8 - 18?
Or did has anyone used a different bolt that would work without having to drill and tap?
thanks
Ray

[Apogee]

I don't know if this would work with the Wilwood kit, but what we do with our C5/C6 GM short-spindle kits is machine a bushing that reduces the hole diameter in the bracket such that we can use 1/2-20 mounting hardware for the 1/2-20 drum spindles. It's cheaper, easier and just as effective as retapping the spindles IMO.

Tobin
KORE3

[AM.MSCL]

Tobin
thanks I was wondering about that also but due to the opening on the caliper bracket did not know if that would work or not.

[Apogee]

What size is the clearance hole in the bracket? I was assuming it was machined for a 5/8-18 fastener like would be used on the alternative drum and/or disc spindles. Is that not the case?

Tobin
KORE3

[AM.MSCL]

Wilwood is needing a .578 opening to tap a 5/8-18 thread for the new bolt.
It is a stock spindle hole currently for a drum with disk spindle.
I did find a place locally that sells the bit and the tap I am going to need.

[Apogee]

Wilwood is needing a .578 opening to tap a 5/8-18 thread for the new bolt.
It is a stock spindle hole currently for a drum with disk spindle.
I did find a place locally that sells the bit and the tap I am going to need.

I wasn't asking what the proper pilot drill diameter is for a 5/8-18 UNF tap, but rather what the hole diameter is through the bracket that you're mounting to the spindle for the purpose of either buying or making a bushing. Also, what do you mean "It is a stock spindle hole currently for a drum with a disk spindle"? The disc spindles have cut down upper bosses tapped 5/8-18. There are two variants of the drum spindle, one with 1/2-20 tapped upper mounting boss and the other tapped 5/8-18, similar to the disc spindle but with a taller boss.

Given what a good 5/8-18 RH tap costs, plus the pilot drill and the time to set everything up and modify the spindles, have you considered just taking it to a machine shop that already has the tools? You could get a quote on some bushings at the same time if you were so inclined and then choose between the two assuming that the bushing solution would work with your brackets.

Tobin
KORE3

[AM.MSCL]

I am betting the stock bolt is the 1/2-20 since the bolt in the wilwood kit is the 5/8-18. I am not sure the actual hole size in the bracket for the caliper due to the tapper in it.
I have talked to a friend that deals with a machine shop and his rate he has to pay is $40-50 an hour.
I talked to the bolt supply house and I looking at $40 for both the bit and drill.
My friend with the body shop is going to check on the tap size and see if he has it.

[70Nova4dr]

What Wilwood kit are you using? I used 140-2285 on my 70 NOva, it was a 4 wheel drum brake car and i didn't have to drill and tap any holes in the spindle, it came with 2 different bolts depending on if you have disc or drum spindles. Good luck

[AM.MSCL]

What Wilwood kit are you using? I used 140-2285 on my 70 NOva, it was a 4 wheel drum brake car and i didn't have to drill and tap any holes in the spindle, it came with 2 different bolts depending on if you have disc or drum spindles. Good luck

I have the same kit but I bought it from someone that installed part of it but never drove the car. I found bolts to make it work but now I am having a new issue that I have called wilwood about.
One rotor/hub will not allow the dust cover to fully go on without losing the ability to spin the rotor. If I only put the dust cover on about half way then the rotor will continue spinning. I checked the part numbers on the inner and outer bearing plus the hubs and the rear grease seal according to wilwood. All numbers match except the hub number but both hubs have the same number. I switch the hub/rotors to the other spindle and make sure the problem stayed with the hub/rotor and it did. I am planning to call wilwood tomorrow to find out what they say.
Thanks
Ray

[Poochie]

For what it's worth, I just went through a C5 upgrade with my '69 Firebird. One thing that I found was that the top mounting hole for the brakes is different on a Firebird than on a Camaro. Not only was the bolt a different size, but the Firebird bolt had a non-threaded shoulder on it that sat in the hole on the spindle, where the Camaro one is threaded all the way to the head. I ended up buying Camaro spindles to make my life easier overall.

Just a bit of a heads up, since it seems that most folks in the industry assume that the Camaro and Firebird spindles are the same.

Cheers,
Ken Chambers

[AM.MSCL]

I talked to wilwood again and they think that one of the races for the inner bearing some how got pressed in a tad to far. So I got to buy 2 new forged hubs to replace the cast hubs with the kit, along with new grease seals. This better work or I am sending them back and will trim the snot tip till the cast one will work.

[staged67gspwr]

I drilled mine as well,its not a big deal just make sure you used plenty of WD40 while drilling and tapping it.