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Old 02-25-2005, 09:49 PM
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Can 2 line brake system be converted to 4?

For my 53 Chevrolet 210 project I will soon need to get a master cylinder and booster assembly. The front brakes are 70's Chev and the rear series 2 Jag. Both were based on the same type of system with one line going to the back and one to the front. Each line is then split into two just before the callipers.

My question is: Will it cause problems if I use a four line master cylinder instead of a two line? This will mean that each calliper get it's dedicated line right from the master cylinder. Will this not actually give better brakes?

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Old 02-25-2005, 11:52 PM
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It won't give better brakes. There is very little flow in a brake line. It will also require that you use 2 proportioning valves (one in each rear brake line) unless there is one in the master cylinder. That doesn't sound fun to to adjust to me.
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Old 02-26-2005, 09:02 AM
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No Improvement

You could just run one prop if you T'd the lines together, ran thru the valve, and then T'd back out...
Seems kind of pointless.
That's similar to how the 4 line diagonal split systems are set. You dont want to use any of those parts on your truck though... valve is preset for the wee car... and dont go diagonal with a master not set up for it either.
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Old 03-02-2005, 09:21 PM
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4 could be better

You may find that the four outlet master cylinder is a stepped bore rapid fill type. These master cylinders work well with the modern , large diameter, multi piston caliper brakes used on 21 st Century cars. They have a higher volumetric displacement than the older type so they deliver fluid to each wheel more quickly. Please be aware that some new master cylinders are designed to be used only with ABS and need to be matched to a control valve to function properly. Using the individual lines with older and as a result smaller displacement calipers would not be harmful but probably not necessary. To block off one of the outlets in each pair, I have used an appropriately sized bleed nipple. It appears you intend joining the old and new systems with the existing brake hard lines; however on a major rebuild on such an old car, you would be wise to use new brake lines just in case there is a gremlin hiding in there. The additional cost is a pittance compared to the the peace of mind you will have. Hope this helps.

Cheers from Australia - Rob.
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Old 03-03-2005, 02:03 PM
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displacement

I have never seen a diagonal split step bore.
Modern caliper pistons are small diameter and so are most masters.

All the step bore master cylinders I've seen affect only one circuit, the front, used for modern low drag calipers which retract the pistons further, no matter the piston size.

The large step bore is in use only at first, to bring the caliper pistons out to meet the disc, then the quick take up valve opens, and it operates as a normal master.
If this was used in diagonal split systems, I would think that uneven braking under light pressure could result, due to the step bore only affecting the primary piston circuit. If it affected both circuits, it would no longer be a tandem master, which separates the primary and secondary circuits in the master for safety.


edit:
I stand corrected. I just looked at a Ford product which appeared to have a diagonal split step bore system. Maybe that explains why so very many of those wear out the RF and LR brake so early....(?) Never the other way....

Last edited by yesgo; 03-03-2005 at 07:21 PM.
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Old 03-05-2005, 03:15 PM
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several GM cars & trucks use a 4 port master cylinder, cant see why it wouldnt work. i do know the 90's sunbird's use a 4 port M/C & the bore is just about the same size a a full size GM car & it uses NO proportioning valve in the system....joe
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Old 03-05-2005, 09:03 PM
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J-body master is only 7/8" bore. It isn't a step bore either. Most of the full size FWD GMs use 7/8-1" and the RWDs mostly use 15/16-1 1/8. There are always exceptions though. I wouldn't have thought I'd see a step bore on a 4 port, but I did.

If the brakes are matched evenly to the weight, you dont need a prop valve... esp w/4wl disc. Prop lets you run larger rears which can help with light braking on street driving though, and it helps counteract the mechanical advantage of self energizing drums.

Unfortunately with the '53 Chevy, you wont know if you need a prop valve until you drive it, or unless if the Jag calipers are really small.

4port master would work fine, just no advantage that I can see with that setup.

Joe, which GM trucks use a 4port master? I am not familiar with them....
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Old 03-05-2005, 10:07 PM
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Thanks guys.

Rob, sorry for not mentioning earlier that actually there were no brake lines on the chassis when I bought the car. The previous owner made some major changes by installing the diff and front suspension part of the chassis with that from a 70's Chevrolet De Ville. The particular car I think is the same as the Constantia and Kommando which are all basically Holdens with names and badging changed to Chevrolet. (I'm actually looking for power-steering box like in the 1st attached pic).

The booster and master I intend using comes from a 1990 4-cyl Opel Monza (see 2nd attched pic of one I had). This master already has 2 valves, one for each rear, which screws into the master and the the brake line into that. On the Opel I had, I actually removed those valves as the one was in the way of the side-draught carbs I installed and I didn't actually notice any difference. The car incidentally had drums at the rear but I changed to discs later without changing the valves and then obviously removed them later as mentioned.

So, I will be installing all new brake lines. The front and rear callipers have also got new seals and dust covers and new bleeding nipples.

The big issue why I want to use a newish booster and master is that they won't need reconditioning immediately where the Jag stuff I have does need a recon before I can use it. Just doing a recon on that will blow my budget out the water. I can get a good 2nd unit (privately or at scrapyards) for about ZAR500 (US$80). The master recon alone is ZAR1100 (US$180) and the booster is double that. And all that is still without 14% V.A.T. For doing that I'll have to save up for at least 6 to 8 months!
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Old 03-07-2005, 08:22 PM
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Have you considered the Holden dual circuit Commodore MC 1 " bore size is close to ideal, if you use one from a Statesman ( I think they are badged the same over there) with the 4 wheel discs and IRS you will have close to the perfect displacement volume for your application if possible use also the hanging pedal assembly which will then give you the ratio you need, these MCs are set up for Vertical Front/Rear split and have a stepped bore with a fast fill set up. BTW the caliper pistons retract by the resistance of the piston seal to distortion. Collette calipers replaced slide calipers because the slides would get crap in them and cause dragging at all times.
I have used the Holden set up on numerous occaisons and had a good pedal feel and straight line braking.

Till later

Rob
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