Where is the best place to install a hold off valve? Is a certin amount of line I need to have after the MC or will anywhere between the distrabution block and the MC work?

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225+0.080 at 10:1
268cam
holley 390
clifford headers
8 3/4 355's lsd
kh brakes
electronic ing

What are you referring to with the term "Hold-off Valve"? A Residual Pressure valve or a Proportioning valve? Neither has any specific distance requirement from the m/c or anything, but I suspect the unfamiliar term is why you've gotten no responses.

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Thom

Cross-threaded is tighter than Lock-tite

i suspect you are talking about a line lock, for doing burnouts or staging. i have mine about midway between mc and proportioning block and it works well.

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1966 Plymouth Valiant, 225, 3 on the tree, 8 1/4 3.21 sure grip, hyperpac, holley 650dp, holset h1c

Not what was trying to ask but good to know. What o am trying to install is a brass block. That the makes the rear drums engage a split sec before the front dics. The way i was told that it was what the e body's us in conjunction with the distribution block and it was stupid proof, which i need, and eliminates the need for a after market proportioning valve

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225+0.080 at 10:1
268cam
holley 390
clifford headers
8 3/4 355's lsd
kh brakes
electronic ing

Ah, unusual term for a now uncommon part. Word makes sense though. As far as I know there is no length/distance requirement for one of those either. I would suggest orienting it vertically (top in, bottom out) to make bleeding easier.

FWIW my approach to tuning a prop-valve is to install it with the knob set at minimum rear brakes (on wilwood's thats to the stop in the "decrease" direction); and then turn it in the "increase" direction one full turn at a time until the rear brakes start to lock up - and then back off a 1/2 turn or full turn depending on what seems appropriate. I only tune it while in the worst case condition (only me in the car, nothing in the trunk, preferably wet pavement). Sounds like effort, but the reality is that I've only adjusted it 2-4 times over the last couple of months and I'm pretty close to where it needs to be. Just need some wet pavement, which we won't see until Oct. at the earliest, to check that I don't have too much rear brakes for that condition.

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Thom

Cross-threaded is tighter than Lock-tite

Thank you for the input. Was a little leery about just installing it and hoping for the best, not really a sound plan of attack when it comes to stopping lol

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225+0.080 at 10:1
268cam
holley 390
clifford headers
8 3/4 355's lsd
kh brakes
electronic ing

In the 70's there were two block types for brakes, the B/E-body (and some post-75 A-bodies) got the block with proportioning and it's a cast item with some metering apparatus inside...the early 70's saw rise of a brass block that just as drilled to meter the fluid however it saw best...mopar used the same block drums front or discs front....I've swapped in discs on late A-bodies an have never seen a difference in braking performance between the "E" body unit in the hyperpak duster and the brass block that I installed in my beater Valiant and later the green duster. It's only worrysome if the rear brake grab before the front calipers even flinch, in which case you need to install one in the line leading to the rear axle to delay their actuation.

-D.idiot

That sounds like the description of a metering valve: it's a device that's part of the combo-block (distribution block with a brk balance warning switch, proportioning valve, & sometimes a metering valve), but not always on all cars. Its job is to restrict fluid flow to the front calipers until the rear drums build 20 psi or so "to overcome the return springs". You can tell if you have one by looking at the combo-block- there should be a round black rubber cap with a short metal pin in the middle that's on the front brake section.

I've used pressure bleeders (10-20psi) on disc brake cars for decades & NEVER had a metering valve actually restrict or limit pressure to the calipers. IMHO you don't need it.

Now a proportioning valve is designed to limit pressure build-up in the rear brake circuit. There are a couple different designs that are in the rear brake section of the combo-block (early K-H systems had an "add-on" prop valve in the rear line if I recall). What's supposed to happen is that with light brake apply the front & rear brakes build pressure equally, then above the prop valve's "cut-in" point (few hundred psi) the valve lets rear pressure build at a lower rate than front. Almost all disc/drum cars NEED a (good) prop valve- otherwise premature rear brake lock-up is nearly guaranteed (BTDT )

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63 Valiant Wagon
225 - 4 bbl

As of 2002 all known to me P-valves allowed 1:1 pressure in the rear brake system until the pressure hit the set point of the valve (known as the "knee point"). Any pressure above the set point was then on a 0.57:1 ratio with the m/c output pressure. Adjustable P-Valves only adjust what that set point pressure is, not the actual pressure ratio as it is fixed internally by the mechanical design of the valve.

I've been vacuum bleeding using engine manifold vacuum instead of a hand pump (way easier on the hands!) and a peanut butter jar with tubes epoxied into the lid for the fluid reservoir, but I'm considering going to the aircraft pressure bleeding method where fluid is pumped into the system at the bleeders. I have a cal-gas bottle that I can install a siphon tube into, just need air pressure regulator capable of only a couple psi. Hum, I need to make a mcmaster order anyway.....

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Thom

Cross-threaded is tighter than Lock-tite