Greetings, I'm having a redundant issue with a leaking metering/distribution block on my 71 Charger SE, 383 4V, original front disc brake car. I just replaced the entire brake system w/ new and or rebuilt quality components, from booster to wheel cylinders, new lines, everything, and have a persistent leaking issue with this metering block. I purchased the Inline prop valve / block kit after I discovered my original block was leaking from the bottom pin area where they commonly leak. I installed the BLK251 / BLK 252 Inline kit. The BLK252 block leaked out the gate, I received a free replacement, that one leaked out of the gate. In the interim, I rebuilt my original with the Muscle Car Research LLC kit, rebuilt it to the letter of instructions, and, it leaks ONLY when I depress the brakes to bleed them. I'm assuming the new seal may need to swell up a bit to seal properly??? It's currently sitting and I'll check in a bit. I'm waiting for a 3rd Inline replacement block which I should have Monday. I'm having a hard time swallowing 2 new defective blocks although anything is possible I guess. Any ideas or suggestions would be appreciated, and or if anyone has a known good one to sell I'd be interested.

New seals shouldn't have to "swell up" to seal.

Well thanks then. So much for that theory.

You got that plug out? I have not had success with he stand alone 70 style metering/holdoff valve. That is staked and also an odd shaped hex head. My inline has been fine. Is it leaking at stem or from under the threaded section? If threaded section, maybe a thin crushable shim to seal it.

Yes, I was able to remove the plug and "rebuild" the block using the new top hat seal and retaining ring which is what the kit consists of. Block still leaks but only when pressure applied during normal bleeding procedure at the wheels, from the pin area of the valve, not the threaded nut area. I'll rebuilt it again and try. Hopefully the 3rd replacement Inline block holds. The two Inline new previous ones also leaked through the pin.

How did you get it off, any specific tool? If leaking at pin, was the shaft pitted, or bent? They can bend easily.

Muscle Car Research used to sell a tool for that. I can’t find it on their website but you can call and ask. It was pricey and around $30 if I recall correctly.

Been to their website before, never saw the tool. They talked about a metric 21mm (I think) socket being used. The ones I attempted it would not take the plug out and rounded off the corners. Between corrosion and staked thread.... Now the later combined valves are a piece of cake. No staking, and standard hex.

Muscle LLC advises to use a 12 point 20MM socket for the nut, which interestingly made me aware that metric sets for some unknown reason all go from 19 to 21. Why do they skip 20? Regardless, I picked up a 12 point quality 20mm socket and it didn't work so good, it started rounding almost immediately. I used a 12" crescent wrench and I got it. One part Muscle LLC doesn't advise in their autopsy, is that after the factory manufactures these, there's a machined rectangular punch at the top on the brass near the rim where the nut goes in, that I suspect acts as a "lock", anti nut back-off preventer and the inner nut shank area is machined like dental bridging to prevent back off. The brass is soft enough to remove the nut and just a slight tap after the rebuild to re-lock it prevented any leakage whatsoever from the threaded area, mimicking what Kelsey Hayes did seemed the only logic, the inner threaded area behind the punched area was deformed slightly which triggered the locking theory. Perhaps that was a mistake on my part, not sure. The leakage was at the pin and, it very well may be bent. The pin did have a little play upon rebuild after install and I did suspect it may of been bent which may of contributed to it's catastrophic failure, I did recently change the spark plugs and may have tapped it causing its demise? But it only leaked when pressure was applied unlike the 2 previous Inline pieces which just leaked outright. Just the same there is a happy ending, I just received my 3rd Inline block hours ago, installed it, and it's dry. In this case, the third one from them was a charm. Thanks all regarding.