Mrmerlin

This is for the clutch operated car owners.
I have been doing a few clutch hydraulic replacements and I have seen a few times so far where the new master cylinder bore is about 1/4 inch shorter than the old part. ( the pistons however are the same dimensions)
I think others have also come across this same problem.
This will prevent the pedal from traveling the distance it used to and possibly cause a dragging clutch system as there wont be as much travel for slave actuation.
So if your replacing the master on the clutch make sure to check the distance of the old and new units if you do in fact have a shorter bore one of the remedies is to remove circlip and the piston from the bore and remove the same amount from the tip of the piston , make sure to also cut a slit into the end so that fluid can still flow at full travel. Good luck, Stan

Fabio421

I made a thread about this a couple of months ago. I had some pics and measurements as well I believe. You can cut part of the spring guide off to gain back some travel. Thats what I had to do and it has worked perfectly ever since. I'll try to dig that thread up later and post it here for a cross reference.

Mrmerlin

Cool Fabio, I posted this as someone else has a few questions about installing clutch Hydraulic replacement parts

OBehave

I had same problem with dragging clutch issues.After bleeding,adjusting "h" pieces on int.plate,swapping MC guts,I trimmed off the piston to get more stroke.Solved the problem!! One thing is the first try I went too far and had the piston overtravel so brake fluid ended up going behind the seal and pumped into the cockpit upon pedal release.

Mrmerlin

Thats a good point you want to measure first to make sure that the piston doesnt go past the fluid feed

Fabio421

Heres the other thread w/ pics and measurements.

https://rennlist.com/forums/928-foru...=clutch+master

heinrich

you guys rock

marton

You can fix that by adjusting the length of the rod from the clutch pedal to the piston.

myself I did this by opening the slave cylinder bleed and adjusting so that gravity did not allow fluid to run out & then turned it back a half turn.

Marton

SharkSkin

I had no issues with mine. Maybe there's less ambiguity about what's needed when you tell the vendor "it's for a '78".

Fabio421

Nope, we ordered a MC for a 78. Read the thread I linked to. You got lucky or you got an old stock MC. Either way, count your blessings.

SharkSkin

I did read the thread -- the way I read it, you bought a '79 MC. Whether by luck or by design, I guess I made out.

Mrmerlin

Marton this is not a clutch pushrod adjustment .
The part that gets modified is on the inside of the clutch master cylinder, its the very tip of the piston that has to be trimmed shorter to give the full throw of the older deeper bored cylinders.
Pay attention to the rear seal on the piston , if you remove too much from the piston it will go past the internal fluid feed and thus fluid will leak out the rear of the clutch master cylinder

Dennis Wilson

When I rebuilt mine on the 78, I discovered that it had been replaced with the later version. Good thing the seals fit both versions.

Dennis

Mrmerlin

for those that might like to review this info,
here is a bump

Daniel5691

Thank you Stan.