Triumph Repair: 1979 spitfire, cone clutch, clutch springs

Question
Hello Howard
my name is Nicholas Caruso and a customer brought us a 1979 Spitfire it's in pretty good shape and is a good runner, but it had a badly slipping clutch. Since the customer was unable to ascertain from the previous owner when the clutch had been replaced. We proceeded to order what we needed from Victoria and machined the flywheel and replaced the clutch kit. The engine has been out 5 times now and each time the clutch is slipping whenever a load is put on the drive train. I have measured the step and that is to spec, when the clutch disc is laid on the flywheel there is about 3/8th of a gap between the flywheel mating surface and the pressure plate.
I have run the car without the slave cylinder installed, and mounted the bellhousing on the engine to see if the throwout bearing is putting pressure on the clutch spring.
This last time that we assembled it the clutch grabs right off the floor which is different from the other times.
Victoria is of no help as they don't have a tech department.

The customer has forwarded me this resource as a possible different direction than we have bee pushing in.

Thank you for your consideration
nicholas caruso

Answer
Hi Nicholas,

Is this car an over drive model? If it is I would check the cone clutch and clutch springs in the over drive because it sounds like you have covered all the basses in the clutch.

I am not sure about the 3/8" stand off of the pressure plate. I have never measured that on a Spitfire but it sounds high. I have not run into this on a Spitfire but have on other cars and I used a rough rule of thumb of looking at the fingers of the pressure plate when it is bolted up with the disk in place. If you see the fingers of the diaphragm flat there is a good chance there is not sufficient clamping pressure on the disk because a diaphragm looses pressure as it is over compressed. Another symptom of this is that the clutch pedal feels too easy to push. The old spring type would clamp harder when compressed more then normal.

This happens too when people miss match components and they need to put flat washers between the pressure plate and the flywheel to space the pressure plate out a little and gain clamping pressure on a diaphragm type pressure plate.

As for the pedal grabbing just off the floor. This was a common ailment of the Spitfire and TR-6 and I found that BLM designed it with not enough travel in the hydraulics. Making them have trouble like grabbing just off the floor. It is easy to fix the later TR-6 by installing the older master cylinder which had a large master cylinder bore. I had several customers at the dealership complain because they could not add carpeting due to the pedal would not go far enough down to release the clutch even when the Spitfire was new.

Let me know about the over drive.

Howard