Topic: Jelly Jar to two bowl MC Question

[heavy]

I just got the dual bowl conversion kit for my '66 289 from CJ ponyparts...

I notice that there is no proportioning valve included with the kit.  Is this optional, or do I need to just get a generic one from a local autoparts store?  I would have thought that they would have given you everything you need to convert the old to new, but maybe not...

I read the FAQ, it says how to adjust a valve, but not whether it is essential.  Oh, and i have all drums on the car.

Thanks,

Micah

[Tim175]

I'm probably wrong here but i thought you only needed a proportioning valve if you had a disc/drum combo? If all drum i didn't think you needed one.

[Soaring]

Tim is correct.  You do not use a proportioning valve with a two bowl conversion if you are running shoes all the way around.  I just did mine last year, so if you have any questions, just holler. Oh, the tubing you get with the kit doesn't fit.  You will have to manufacture your own lines.  A lot of guys have curled up lines at the MC, but mine works just great as it is. Here's a pic of mine.  Looks like I have a painting project, huh? 

[zray]

you may not have to have a prop valve, but if your rear brakes are locking up before the fronts, you need one.

Z. Ray

[Soaring]

The front brakes get two lines to them.  The back ones do not lock up before the front ones.  You are still thinking front disks and rear shoes. 

[heavy]

Yeah, this is definitely drums all around.

[zray]

The front brakes get two lines to them.  The back ones do not lock up before the front ones.  You are still thinking front disks and rear shoes.

no I'm not. Just because a car is all drum doesn't mean it would not benefit from a prop valve if the rear brakes are locking up first.

Z. Ray

[Soaring]

Each of the front brakes get a line of its' own.  The design is so that there is more pressure to the front brakes as opposed to the rear, but only a determined amount.  This is basically the same design as the jelly jar as it came from the factory.  The only difference with a two bowl is that if the front or back line blows, you still have either the front or back brakes, whereas if the jelly jar blows a line, the entire braking system is lost.  The back brakes will never lock up before the front ones simply because they are not receiving the same amount of pressure.  Theoretically you are correct.  The prop valve is used to lessen the pressure given to the rear brakes when there are disks on the front, but the two systems are different.  You could use a prop valve on the rear of an all shoe system, but you will just be wasting your money, and if you don't get an adjustable prop valve, you will be going through a lot of headaches to get it because you can't adjust it properly when not using one was the ticket in the first place.   The 1967 Mustangs were the first year to come out with the 2 bowl MC.  They did not have a prop valve on them.  Now, if a prop valve was necessary, why didn't the Ford engineers have  them put on the 67's? Answer?  Because they are not necessary on an all shoe system. 

[zray]

I didn't know you could even buy a non adjustable prop valve.

on a street car car, with a marginal drum system, ok, you can get by without a prop valve on the all drum cars, only because accountants are second guessing the engineers.

I've driven numerous high performance cars with all drum brakes (before discs were common) that benefited from having  a prop valve added.

but you are right, you don't need a prop valve, But I need one.

Z. Ray

[Soaring]

Do you have disks on front Zray?  Yeah, you can buy non-adjustable prop valves.  http://www.ecklerschevelle.com/product.asp?pf_id=602521A&dept_id=1050

[zray]

I have a basically stock brake system, discs/drum  on my GT-350. I did change to a dual reservoir master cylinder & better pads, shoes, and rotors. No power assist, but it will lock the wheels at highway speeds, so I'm satisfied with the stopping performance.




I have driven a lot of all drum cars in the past, mainly old Corvette's. They were helped by the addition of an adjustable prop valve.

But  I have to add, my recollections of my driving exploits are greatly  enhanced by a poor memory...


Z. Ray

[Soaring]

Yeah, I have CRS disease too.