Looking for some help with this setup. I'm on the second clutch already (first one was from the junkyard so it may have been bad to start with). I've got a 1953 331 chrysler motor in a T coupe (I'll get new pictures up here someday soon). It's connected up to a 4 speed saginaw out of an 81 olds with an adapter from Hot Heads. I got an aluminum flywheel from a boat that was machined for an 11 inch chevy clutch. The problem comes in with the hydraulic setup I think. It's got one of those Pete and Jake setups with brake and clutch master cylinders, pedals, and all the linkage. The clutch master is 3/4 bore. Since there wasn't room for the the included slave cylinder (it's a puller), we substituted a piece that I believe is from a 90s ford truck. It's also 3/4 bore but is a push style. The problem we had when we hooked it up with the brand new clutch is that it couldn't push the clutch fork far enough to disengage it. Easy I thought, I'll just make a longer rod to go in between the slave cylinder and the clutch fork. Thinking back, this was a bad idea but it didn't *feel* like it was slipping at all. Maybe 70 miles and a couple days later, the clutch isn't engaging at all anymore and I'm stuck on the road. Called my dad to have him bring me the original rod to go in between the slave and clutch fork. Got it in and it won't fully disengage the clutch again but we got it limped home by starting in 3rd. It actually feels like it has more power too (probably cuz the clutch must have been slipping a tiny bit almost the whole time). I'm pretty sure I'm going to need to redo one or both ends of the hydraulics on this car but I don't know where to start. I took some measurements and this is what I came up with. The clutch fork fully relaxed is 2.5 inches from the bracket the slave is bolted to. The longer rod I made is 5 inches from the bracket when fully extended (pedal pushed in). I think that means I need 2.5 inches of travel in the clutch system. With the current setup, I only have about 1.25 inches of travel. I probably need to move to something GM made or maybe even just something that has an 11 inch clutch but I don't know what that would be out of or where to get the parts. Wondering if someone has a hydraulic clutch set up similar to this where they could take some measurements and help me figure out what parts I should try. I'll post pictures of the offending parts in case my overly long description doesn't make sense. Please let me know if I'm going down the wrong track with this- this is our first attempt at building a hot rod so I'm sure there are multiple things we may have botched up.
a few Basic rulesof Hydraulics have been broken here.You need to have a smaller bore to push a larger one( e.g the pump on your hydraulic jack) and somewhere here there will be ratio tables to work out the correct size .At a pinch ,I would try a larger bore slave cylinder from something else.
Correct me if I'm wrong but wouldn't a larger bore slave get me less travel to push that clutch fork? The way I'm thinking, it should also make it easier to push in the clutch. In a floor jack that makes sense since you're moving something heavy. Anyways, in that P and J kit they included a 3/4 slave but it was a puller when I needed a pusher. I'm guessing they built the kit for an application that wouldn't need this much travel.
Yes ,you are right ,but in a clutch ,when it disengages ,the fingers only move a minute amount compared with the length of stroke demostrated by the slave.So in actiual fact the slave cylinder really only needs to move .Say 1/4" ( 5mm) to diengage the clutch. i would go back to basics in your situation. 1/Start by examing the spigot bearing.Is it a bush or a needle roller? ( i had a couple of those 331's and i can envisage the problems a spigot bearing is going to present).Either measure it and make sure the input shaft on the trans is smaller to give you plenty of free movement,or pull it out and test it on the shaft. 2/ Is the trans input shaft smooth?,No ridges or marks which would make it grab in ther spigot bearing? 3/How is the input shaft bearing in the trans case? Can you turn it wthout any sound? 4/ Does the throwout bearing move smoothly on the trans input shaft mount? It needs to be able to go in and out without any restriction what so ever.You did say you had clutch slip before..a throwout not being able to return properly will do that. 5/ Did you check the 'crank to trans mount bore runout' ? .If the trans is not centred correctly,and is off to one side by a few thou. it will drag in the spigot bearing besides creating other problems. 6/ I assume the ratio of the throwout bearing is compatible with thrust needed to disengage the clutch by pushing on the fingers? 7/ what is the overall condition of the trans?.No seized synchro's etc ?A set of seized needle rollers in the main shaft will let the trans work but create enough drag to prevent the gears from disengaging when you try to change up or down. 8/ Make sure the trans isn't pushing against the end of the crankshaft... 9/ Did you put the driven plate on the trans input shaft and make 100% sure it moved along the shaft easily? I've always done that ,having been taught in the late 60's to never guess everything will be OK and then find a clutch doesn't work becvause of some minor detail like a dragging clutch plate center.
Anyone else have an opinion of what it might be? Maybe someone with an 11 inch chevy clutch in their ride can measure what kind of throw they have on their fork from engage to disengage....
I would suggest finding a slave with a smaller bore or moving the point where the rod pushes the clutch fork closer to the fulcrum. That will also give you more travel on the T.O. bearing. It sounds like when you put the longer rod in the slave you may have used too long a rod and lost your free play causing the clutch to not completely engage.
Is the fulcrum in the bell house fixed? Can it be installed backwards? When all is said and done, with the clutch pedal depressed, you should be able to put a .040 feeler between the disk and the flywheel.
In my car when I got tired of fooling with a same size master and slave cylinder, I bought the biggest diameter master cylinder Tillson makes. It works great. Have to push a little harder, but not bad. May need a stop to keep from going over center.
Would a larger bore master push the existing slave further than it goes now or do I need to replace the slave with something else too? I'm guessing this is another case of try one thing and see if it works, then try something else but just thought I'd ask. So many things on this car seem to be do and then re-do two or three times before it finally clicks into place. The nature of hot rodding maybe...
What is the conditon of the Master cylinder bore?.It's just like the brakes,it has to be perfect.if theres any leakage,you are not going to get full stroke . Try something else...: What is the distance form the pedal pad to the center of the pedal bushing? How long is the other end of the pedal arm that pushes the cylinder piston in? the difference is pedal the ratio. How long is the distance from the throw out bearing to the throw out arm pivot? ..and finally how long is the arm to the slave piston? If the ratio is ideally 1:1 ,is the throw out arm ratio shorter or longer than the pedal ratio?. i
Yes a larger bore master will make the slave travel farther. Say you have a 3/4" bore master and a 3/4" bore slave. If the piston in the master travels 1 inch then the piston in the slave will travel one inch. travel. Change to a 1" master and for the same one inch of travel in the master the slave will travel farther. Say you change to a 1" master and have 1" of stroke available the displacement will be pi times the radius squared times the stroke. 3.14 x .5 squared x1 = .785 square inches of displacement. Now you need to find out how much this displacement will move the 3/4" bore slave. stroke of slave = .785 divided by pi times .375 squared the stroke of the 3/4" bore in this case would be 1.78 inches so by changing to a 1" bore master you would gain .78 inches or about 3/4" of travel for the same 1" of travel of the master. Now I have really taxed my brain on this one. My fav subject in school was solid geometry and physics so some of you eggheads out there check my math on this, I need a beer!
FWIW I have a setup in my Model A on a T5 with a 3/4" master and 3/4" slave. The recommendation I got was to use a 3/4" master (from the manufacturer of the slave) to start with. If that was not enough travel use a 7/8" master. After that they (the manufacturer of the slave cyl) claimed if you went any bigger that it would probably run out of travel (internally on the slave). I have the 3/4 master in the Model A with a T5 out of a 92 mustang and a Hays 95-201 clutch set, on an aluminum wheel (with the iron friction insert for the clutch). I don't have enough travel, the clutch won't disengage fully until I get the adjustment so tight I think there is a preload on the pressure plate fingers (not good). I checked all the stuff that Mercmad listed before I put it together (all sound advice too). I will add the 7/8 cylinder this winter (or maybe fall) and adjust accordingly. I would do it sooner but the engine is out of the car right now (bad load of brand name fuel in Cali, on the bright side the machine shop THINKS they can save the Crank and the Heads ) and you kind of need the engine to hold up the clutch to adjust the mechanism, ya know?
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