SpitFire6 Posted May 31, 2020 Report Share Posted May 31, 2020 Hi, I believe there are 3 choices for a slave cylinder on a GT6. 5/8", 5.5/8" & 6/8"? If I measure the diameter of the exposed piston end, should this be the same as the internal diameter of the piston? The end diameter is way smaller than even the 5/8". The cylinder is seized solid & will not come out. Suspect it's been seized for many years while on the car. No info on the body. Cheers, Iain. Link to comment Share on other sites More sharing options...
NonMember Posted May 31, 2020 Report Share Posted May 31, 2020 I think the end is smaller than the bore so no good for measuring. If you change both sides you'll know they're the same, which is probably all that really matters. Link to comment Share on other sites More sharing options...
dougbgt6 Posted May 31, 2020 Report Share Posted May 31, 2020 The very late mk3 had 7/8ths, but no longer available. Doug Link to comment Share on other sites More sharing options...
SpitFire6 Posted May 31, 2020 Author Report Share Posted May 31, 2020 Hi, so 5/8", 5.5/8", 6/8" & 7/8". I am curious about what I had in the back. Both have been replaced with new. Can't remember. LOL. I just drilled the plate out on the backside and through to the inside. Now the wife has gone to work I am heating it in the oven @ 230c. Will drop it in some tap water and bang the cylinder out. If it doesn't come out I will give up on it. Cheers, Iain. Link to comment Share on other sites More sharing options...
Pete Lewis Posted May 31, 2020 Report Share Posted May 31, 2020 or fit a grease nipple and get the wanner to pump it out Pete Link to comment Share on other sites More sharing options...
SpitFire6 Posted May 31, 2020 Author Report Share Posted May 31, 2020 12 minutes ago, Pete Lewis said: or fit a grease nipple and get the wanner to pump it out Pete Wanner? unnaturally pale, esp from sickness, grief, etc? I can't hydraulically remove it as It has a 10mm hole in the backside now. Just dunked it. No joy. will give it 60 mins in the oven and then going to dunk it in phosphoric acid while holding breath. Leave it for 24 hours. Will see if it dissolves more of the alloy. Cheers, Iain. Link to comment Share on other sites More sharing options...
dougbgt6 Posted May 31, 2020 Report Share Posted May 31, 2020 Iain, is your GT6 a very late 73? Does it have Sundim glass and a servo? Yes? Then it’s 7/8ths, If not it’s earlier, which is better because you can’t get the 7/8th parts. db Link to comment Share on other sites More sharing options...
SpitFire6 Posted May 31, 2020 Author Report Share Posted May 31, 2020 Hi Doug, The only GT6 part of the car is the Logbook. Its a "Triggers Brush". It has the skinny manual rear shoes. It was a single system but now tandem after the rear flexible leaked & I lost brakes. That's when I found that the cylinder was seized despite it going through many MOT's. Seems that the Quaife for one reason or another caused a pass every time. The car is in lockdown at the moment hundreds of miles away so I can't check its partner. Nothing else better to do I thought I would check this one. It's sitting in acid at the moment fizzing away. Hopefully, something is left to measure tomorrow! Thanks, Iain. 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted May 31, 2020 Author Report Share Posted May 31, 2020 Hi, Still fizzing! The alloy has a soft water-soluble charchaol coloured coating. Not sure why I can smell sulphur compounds? Cheers, Iain. Link to comment Share on other sites More sharing options...
thescrapman Posted June 1, 2020 Report Share Posted June 1, 2020 Did you drill a hole in the end and try drifting piston out? if not Why not just cut it in half? You can then measure the hole, or a bit of piston Link to comment Share on other sites More sharing options...
SpitFire6 Posted June 1, 2020 Author Report Share Posted June 1, 2020 (edited) Bang bang out. It's 5/8". Smallest of the bunch. Less chance of looking locking up I thought until I saw this from a Book. Is this true??? surely not! Cheers, Iain. Edited June 1, 2020 by SpitFire6 Link to comment Share on other sites More sharing options...
poppyman Posted June 1, 2020 Report Share Posted June 1, 2020 Apparently so Iain, have heard that before. I don't know the mathematics involved but i am sure someone on here will. Tony. Link to comment Share on other sites More sharing options...
thescrapman Posted June 1, 2020 Report Share Posted June 1, 2020 The bigger the rear cylinder the more pressure is available to move the shoes for the same pedal pressure, but the longer the pedal travel. so I think th article has it back to front. 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted June 1, 2020 Author Report Share Posted June 1, 2020 44 minutes ago, thescrapman said: The bigger the rear cylinder the more pressure is available to move the shoes for the same pedal pressure, but the longer the pedal travel. so I think th article has it back to front. Is it not more force not pressure or in this case same same? Link to comment Share on other sites More sharing options...
Clive Posted June 1, 2020 Report Share Posted June 1, 2020 41 minutes ago, SpitFire6 said: Is it not more force not pressure or in this case same same? force=pressure x area. So for a given pedal pressure, a larger piston will apply a larger force on the shoes. too much rear braking is best avoided..... Link to comment Share on other sites More sharing options...
SpitFire6 Posted June 2, 2020 Author Report Share Posted June 2, 2020 Hi, including a spitfire one, there is now four available as the fifth is not available. so 5/8", 5.5/8", 5.6/8", 6/8" & 7/8". I had half the smallest & now probably the smallest available. No wonder the disks & tyres do not last long. LOL. Bigger might give more feel. My front are a knats less area than OEM GT6. Cheers, Iain. 1 Link to comment Share on other sites More sharing options...
SpitFire6 Posted June 17, 2021 Author Report Share Posted June 17, 2021 A couple of years have passed since seen car. Went with smaller. Get back soon I hope. 1 Link to comment Share on other sites More sharing options...
Peter Truman Posted June 17, 2021 Report Share Posted June 17, 2021 I've just replaced the daughters Mk2 Spit rear slaves after checking the manuals etc with the correct 0.75in NOS Girlock originals, the seized ones I had fitted 20years ago were Vitesse 0.7in units as I had them as spares, If I remember correctly my research showed Mk1/2 were o.75, later Mk3 & 4 went smaller at 0.625 and 1500's back to bigger to 0.7in. So now i've rebuilt the Girlock 0.7's as there was no bore damage cleaned with meths and a dremmel round softish scour sponge type bush a couple of times up the bore, bores perfect, piston no rust then new seals and boots. Prefer tp keep the Girlock's rather than unknown aftermarket? Link to comment Share on other sites More sharing options...
DVD3500 Posted June 18, 2021 Report Share Posted June 18, 2021 I believe the switch over was just before the 1500 come in which is more confusing as it arrived in the US before in Europe. Link to comment Share on other sites More sharing options...
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