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Old 09-08-2019, 06:29 PM
nytrainer's Avatar
nytrainer nytrainer is offline
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Default GM front disc setup question

I have complete disc brake front end (uca/lca, spindles, rotors, calipers, etc) as well as brake MC and booster. I believe this complete setup from ‘70 Monte Carlo. It has round (same size) control arm bushings but was under impression 70 and newer used oval bushings?
To use this setup on a 70 Lemans that has manual drum brakes what is needed to complete the installation? I realize brake lines but what about distribution block. Doesn’t appear to have had a hold off valve mounted near the MC like some of the aftermarket setups use. Keeping rear drums too. Is there a way to date these parts?
Lastly, being a single piston caliper would original 14” rally 2 wheels from this 1970 Lemans clear. I realize there were different wheels for the 68 4 piston calipers but thinking by 70 factory wheels would clear both drum and disc brakes?
Thanks

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Old 09-08-2019, 06:46 PM
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I thought 64 was the one that could have oval bushings, or not.

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Old 09-08-2019, 07:48 PM
'ol Pinion head 'ol Pinion head is offline
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'64's & 65 A-bodys had round bushings, one small diam, one larger diam in the lower control arm. Can ck my stock of lowers, but memory serves right one bushing is smaller diam. These lower arms are the only ones with the small pass through area for the front shock.

From multiple hundreds of A-body's disaassembled, the oval bushing/large round bushing lower control arm began on '66 model A-body's & went up through '72 models. Very common style front lower control arms.

The large/large round bushing A-body lwr control arms have been described as '66+ Chevelle SS lower front control arms by the Chevy crowd, but many many real SS Chevelles had a mix of large round/oval bushing on one side control arm, as well a large round/large round on the opposite side, sometimes even both side lwr arms had a oval bushing.

All told there are even more styles, as '69-72 GP & 70-72 Monte are same basic shape but their own styles. One has a piece of flat steel that's welded-sideways in one of the lwr legs, have to look at GP lwrs I have.

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Old 09-08-2019, 08:10 PM
'ol Pinion head 'ol Pinion head is offline
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Quote:
Originally Posted by nytrainer View Post
I have complete disc brake front end (uca/lca, spindles, rotors, calipers, etc) as well as brake MC and booster. I believe this complete setup from ‘70 Monte Carlo. It has round (same size) control arm bushings but was under impression 70 and newer used oval bushings?
To use this setup on a 70 Lemans that has manual drum brakes what is needed to complete the installation? I realize brake lines but what about distribution block. Doesn’t appear to have had a hold off valve mounted near the MC like some of the aftermarket setups use. Keeping rear drums too. Is there a way to date these parts?
Lastly, being a single piston caliper would original 14” rally 2 wheels from this 1970 Lemans clear. I realize there were different wheels for the 68 4 piston calipers but thinking by 70 factory wheels would clear both drum and disc brakes?
Thanks
Multiple different ways to go for front to rear proportioning on a front disc rear drum setup.
-stock 70 A-body disc brake setup with a reproduction hold off valve under the disc brake master. '70's also used a small brass valve (resid pressure(?) on the front of the frame crossmember where the rear end hose attaches.
- '71-72 A-body style stock disc set-up, uses the first integral proprtioning valve. '71-72 disc lines can also be configured with that particular style prop valve or a brass replacement style which mounts under the disc brake master cyl. Have gone that way many times plumbed with a disc/drum proportioning valve & a small steel OEM mtg bracket from a 76-79 Seville. Very clean set-up, ESP when the engine in running headers. Inline Tube has marketed a very similar setup calling it a "conversion line" setup with their small bracket.
-Adjustable aftemarket proportioning valve in line going to rear brakes. Have had numerous partscars that came in with these, often with '73-77 A-body disc spindles/rotors. Personally not a fan of either. Too easy to tamper with the adj prop valve when under the master. Often times have come across them mounted up in the unboxed center frame rail.

On the '70 rally two 14x6 wheels, they will work disc or drum. '69 drum brake A-body's can do the same, as all '69's used the JA rallyII wheel whether factory drum or disc.

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  #5  
Old 09-08-2019, 08:30 PM
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Did you get the steering arms from the Monte Carlo? if not you will need to drill out the Lemans arms to 1/2" Ø to fit.

Mark

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