I do not recall but I drilled a hole thru the dust boot groove thru the piston shaft and dropped in a steel pin to keep the piston from ever moving. That was in 1981. No removal required, no bleeding just drill a small hole outside the fluid chamber and one can use a nail or what ever fits the hole size you drilled.  With that upgrade and PORTERFIELD R4S brake pads I can lock up all (4) tires with no other modifications. Best upgrade for the least amount of money I ever did.   In a message dated 3/22/2025 4:56:58 PM Central Daylight Time, detomaso@server.detomasolist.com writes:  All, A friend in Europe is struggling to plumb his brake system. I would have sworn that the brake line fittings going into the bottom of, and out the top of the pressure reduction valve are all the same. He’s reporting that the inlet at the bottom is different.  Does anybody know for sure what the size or sizes of the fittings are? Mike  Sent from my iPad_______________________________________________  Detomaso Email List is not managed by POCAPosted emails must not exceed 1.5 MegabytesDeTomaso mailing list -- detomaso@server.detomasolist.comTo unsubscribe send an email to detomaso-leave@server.detomasolist.com To manage your subscription (change email address, unsubscribe, etc.) use the links above. Members who post to this list grant license to the list to forward any message posted here to all past, current, or future members of the list. They also grant the list owner permission to maintain an archive or approve the archiving of list messages. I do not recall but I drilled a hole thru the dust boot groove thru the piston shaft and dropped in a steel pin to keep the piston from ever moving. That was in 1981. No removal required, no bleeding just drill a small hole outside the fluid chamber and one can use a nail or what ever fits the hole size you drilled. With that upgrade and PORTERFIELD R4S brake pads I can lock up all (4) tires with no other modifications. Best upgrade for the least amount of money I ever did. In a message dated 3/22/2025 4:56:58 PM Central Daylight Time, detomaso@server.detomasolist.com writes: All, A friend in Europe is struggling to plumb his brake system. I would have sworn that the brake line fittings going into the bottom of, and out the top of the pressure reduction valve are all the same. He’s reporting that the inlet at the bottom is different. Does anybody know for sure what the size or sizes of the fittings are? Mike Sent from my iPad _______________________________________________ Detomaso Email List is not managed by POCA Posted emails must not exceed 1.5 Megabytes DeTomaso mailing list -- [1]detomaso@server.detomasolist.com To unsubscribe send an email to [2]detomaso-leave@server.detomasolist.com To manage your subscription (change email address, unsubscribe, etc.) use the links above. Members who post to this list grant license to the list to forward any message posted here to all past, current, or future members of the list. They also grant the list owner permission to maintain an archive or approve the archiving of list messages. References 1. mailto:detomaso@server.detomasolist.com 2. mailto:detomaso-leave@server.detomasolist.com