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| 80mm Brakes for 73 Revcon [message #60688] |
Mon, 19 October 2009 14:05  |
rowing guy
Messages: 31
Registered: October 2009
Location: Outside Philly
Karma: 0
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Hey Folks,
So, while I don't have a GMC, I will have something close, a 73 Revcon aka as a Flatnose. As I'm sure you know it has the 455 Oldsmobile Toronado FWD system and I want to upgrade to the 80mm brakes. One bit of history is that it has been sitting for a very long time and several mechanic friends recommended I replace the calipers, rear brake cylinders and hoses, so the fun begins.
My question is of the parts below, are they all for the same vehicle (84 Chevy p/u) or are they a hodgepodge from a variety of different sources? The part numbers below are no longer good at Autozone and I wanted to go to Advanced Auto Parts anyway as I have several coupons that could add up to some nice savings. Is there a listing of other part numbers or what the vehicle the parts come from? I'm not sure how to order these parts from Advanced.
Scott
80 MM Front Brake Caliper Upgrade
80 mm Caliper numbersJim Wagner suggested the 84 1/2t 2wd Suburban with JB7, JD7 brakes.
1984 CHEVROLET TRUCK C20 3/4 TON P/U 2WD WITH JB7, JD7 BRAKE SYSTEM
ken
--------------Parts needed to change over to 80 mm caliper's on the front wheels are Autozone and are as follows:
2 ea Banjo bolt, p/n 313940, $1.99
1 ea Caliper, left side, p/n 90185, $12.99 + core charge ($17.00)
1 ea right side, p/n 90184, price same as above
4 ea Caliper mounting bolt, p/n H5004, $1.29
1 ea Brake pad set, p/n 1534, $37.99 (these are Performance Friction carbon metallic pads)
1 ea Flexible hose, left side, p/n 77320, $24.99,Wagner F110424,NAPA 38563-702
1 ea right side, p/n 77421, price same as above,Wagner F110425,NAPA 36954-726
For the brake hoses, try Raybestos # BH38563 & BH36954. You will need two
5/8 national fine jam nuts to attach the hoses to the bracket at the frame.
You will have to slightly alter and move the bracket that is in the middle
of the hose. The steel tube end that fastens to the caliper will have to be
bent a little to clear the upper ball joint.Denny
2 ea bracket clip, p/n H1457, $1.29
2 ea jam nut (don't have AutoZone number for this)
2 ea bolt and nut, ss, ¼ x 1" (not an AutoZone item)
One of the benefits of going with an 80 mm caliper is it applies, I'm told, approximately 1000 psi more braking force vs. original caliper. The difference is noticeable.
Although there was some degree of controversy on this subject a number of months back, you may want to consider going to a larger master cylinder if making the switch to larger the calipers. If so, it's available from
Autozone, p/n 10166, $53.43, and does require an ~ 0.010" longer brake rod (p/n GM 5469384)(between master cylinder and brake booster) as well as a modified mounting bracket. If you need further details on this
modification, let me know. Paul Bartz
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| Re: [GMCnet] 80mm Brakes for 73 Revcon [message #60719 is a reply to message #60688] |
Mon, 19 October 2009 19:08  |
GMCWiperMan
Messages: 1248
Registered: December 2007
Karma: 1
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Senior Member |
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Scott,
The 10 pictures in this album include photos of the BrakeWare packages
for the various auxiliary parts. You should be able to enlarge them
enough to easily read those numbers, which should still be good
crossreferences.
http://picasaweb.google.com/ken0henderson/GMC80MmBrakes?feat=directlink
http://tinyurl.com/yjgklkn
Also shown is the location of the "bump" which must be ground off to
clear GMC wheels; you may not need to do that.
Not shown nor mentioned is that you must bend the rigid tubing at the
banjo fitting end of the flexible hoses. That quickly becomes obvious.
IIRC, it was also necessary to grind a little around the area of the
banjo fitting for it be oriented properly. IIRC, I removed the mounting
clip from the flexible hose and secured the hose to the A-arm with
TyWraps. But that happened 7-9 years ago.
The part numbers you quoted are for assorted vehicles. The PU reference
is primarily for the calipers.
HTH,
Ken H.
Scott Brown wrote:
> Hey Folks,
>
> So, while I don't have a GMC, I will have something close, a 73 Revcon aka as a Flatnose. As I'm sure you know it has the 455 Oldsmobile Toronado FWD system and I want to upgrade to the 80mm brakes. One bit of history is that it has been sitting for a very long time and several mechanic friends recommended I replace the calipers, rear brake cylinders and hoses, so the fun begins.
>
> My question is of the parts below, are they all for the same vehicle (84 Chevy p/u) or are they a hodgepodge from a variety of different sources? The part numbers below are no longer good at Autozone...
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| Re: 80mm Brakes for 73 Revcon [message #60793 is a reply to message #60688] |
Tue, 20 October 2009 10:17 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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Senior Member |
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>Scott Brown wrote:
> Thanks Ken, I appreciate the help and tips. So, after so long, are you glad you did it? >Was it worth it?
Scott,
I made this change to my GMC a few years ago, mainly because I had the rubber hose go bad the day before a trip, and the only hoses that were readily available in town without ordering were for the 80 mm. calipers.
I'm pleased with the results, and have a stock size master cylinder. It has more pedal travel than I would like, but I think that's because the rear brakes are way out of adjustment (want to redo them top to bottom but haven't gotten to it yet.) Sounds like Gary Casey knows more about brakes than I've ever even wondered about, but along with more apply force from the greater piston size, I think (but can't prove) one of the things that you get is a "stiffer" caliper that doesn't deform as much under hard applications while hot. (calipers are essentially big C clamps, and flex a lot more than you might think . . . Added stiffness maintains better pedal feel and better apply pressure.)
One thing I don't particularly like is how much you have to bend the steel part of the new hoses to make them work. It just made me squeemish that I was going to screw them up, but I haven't had any problems. Also, they don't come up with the point of rotation of the hose (as the wheels turn) as close to the center of the wheel as the original ones do. This leads to the hose "changing length" and drooping on wheel turn more than I would like. I tie-wrapped it in a couple of places as it gets close to one of the tie rod ends as I recall. I think the answer there is some nice steel braided lines with the right fittings to position everything correctly.
I don't know if Jim Kanamoto sells braided lines specific to the 80 mm calipers or not. But, if he doesn't they would be pretty easy to make up. I was in a hurry to get my coach mobile when I put mine on, but yet another thing to tear into later.
So, a longish reply, but overall, I think it is a good improvement and when I did mine, the calipers were actually cheaper than the original ones.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: 80mm Brakes for 73 Revcon [message #60814 is a reply to message #60802] |
Tue, 20 October 2009 12:01 |
roy1
Messages: 2126
Registered: July 2004
Location: Minden nevada
Karma: 6
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Senior Member |
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I too went with the 80mm calipers and 1 size larger rear middle wheel cylinder. I agree with Ken it was a good mod.I am running the stock master cylinder. If the Revcon is using the same capacity master cylinder it should work as well for you. It is important that you also use the new ceramic pads or carbon friction pads. I don't know about your rear shoes. I would try to use a good friction material on them. We can get police car type shoes or carbon type shoes for the GMC thru Jim K.
Roy
Roy Keen
Minden,NV
76 X Glenbrook
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| Re: 80mm Brakes for 73 Revcon [message #60868 is a reply to message #60825] |
Tue, 20 October 2009 20:32 |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
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Senior Member |
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> I noticed that Leigh Harrison sells a braided stainless 80 mm hose set here:
Michael,
Thanks, those look good. I'll have to add them to the list. I need to do the rear brakes 1st, and need to find a job before I do those. But, looks a lot easier than making them up from scratch.
Craig Lechowicz
'77 Kingsley, Waterford, MI
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| Re: 80mm Brakes for 73 Revcon [message #61065 is a reply to message #60688] |
Wed, 21 October 2009 22:38 |
rowing guy
Messages: 31
Registered: October 2009
Location: Outside Philly
Karma: 0
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Again, great info here folks. thanks. I'm gonna order the braided lines, should help with pedal feel with a stock master cylinder. Just don't tell the misses....
Scott
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