Clutch pressure plate to flywheel clearance

huh? What you askin? Anyway, street clutch plates have compressed and uncompressed thickness spec in your WSM because of the marcel spring. There is a wear/thickness spec for your PP and FW. The throwout bearing system free floats and the disc to plates gap will settle to their own free places like your brake pads do on your brake calipers UNLESS there is improper factory spec for the uncompressed/compressed plate thickness. This is often a problem when getting plates resurfaced even those experienced like Friction materials co. because they are 100% lazy and you always have to check their work. A plate that is too think will not allow clutch release. A plate too thin will either slip immediately or have a very short life. So read your WSM! Hope that helps.

 

I think there are too many variables to give you an opinion. It seems like it's all about clamping force versus enough travel for a clean release. Have you tried the manufacturer for that information?

What is it for?

 

Craig,

The gap is not really that important. Below is the formula you need to see if it will work.

Torque that a clutch can transmit :

T = NfFR

T = torque in ft lbs
N = number of friction surfaces
f = coefficient of friction (.25 for stock, 0.32 for copper-ceramic, 0.5-1.2 for carbon composite materials)
F = Clamping force in pounds
R = radius in feet (inside radius + outside radius)/2

Target between 1.25 to 1.5 times the peak torque rating of the engine for the amount of torque the clutch can transmit.

Instead of measuring the gap, you need to measure the clamping force. Note it will be pretty stout, I did not run the numbers but expect it to be in the 800 to 1600 lb range.

Don't forget the marcel spring will be compressed at the height you are looking for the clamp load.

Cheers Jim

 

The information you are looking for is something a clutch manufacturer would use. It's not something I've seen as a spec for an "end user". I've had clutches rebuilt and took relative measurements before sending the parts out in case I had issues later but it never was a problem.

Checking bearing clearances is an entirely different thing and is part of the engine building process regardless of where you bought the parts or who did the machine work.

 

There is no such thing. The WSM has the specs for any car based on OEM dimensions and OEM parts. A plate on a 250 gt would have specific dimensions to match the required set-up height of the system of FW,PP and trhow of the T/O bearing. Varying from OEM you can have a thinner plate if say someone brass faced the FW to thicker than OEM dimensions but the overall package still needs to fit. You can do thinks like improve hard connection to the driveline by deleting marcel springs but the spec compressed needs to be kept. Once you go out of OEM like say put a multi plate Tilton Clutch package on a home made 308 racecar, Tilton would do all the math to fit the clutch pack into the space available and for their T/O bearing set-up for the most unlimited sytem. They could also build within the throw of the OEM T/O bearing depending on available parts, conditions, and costs. Sometimes it is just cheaper and better to have a full tilton system for example. Still I'm not sure what you are tyring to do or what specific question you are asking.

 

P400...I'm making a clutch(clutches actually) out of 4340 billet logs for a couple of ex works cars(multi disc, "birdcage types")...that said, I have not got a clue what you are talking about!

This is when text books usually are getting in the way of practical applications...it is-in my own experience-usually best NOT to try and reinvent the wheel.
Your pic looks like a std re-man 250 clutch...no?

If so, be happy, install it, and drive it...
Likely that it will fail due to oil surface contamination from leaks far before "pre-mature"wear...honestly..
You will NOT get the service life from these sorts of parts thAt you will get from a NAPA clutch for a Camry!!!

If for a 250, the truth ius that you are not likely much above 200HP, certainly not above 250HP in the REAL world...that said, "adult" style driving habits ought to yield many miles of adequate service life from the unit which you've illustrated in picture,
ciao!

 

To get back to your basic question, 0.35 - 0.22 = 0.13 compression on the clutch disc, seems to be in the ballpark of what I have seen building clutches. Never actually measured it before, but it seems the pressure plate always has about an 1/8 inch gap before you have to start torqueing the bolts.

Typically you never measure this though. If the clutch guy has done his job you just bolt it on and go. Technically he should have run the calculations. I was under the impression you wanted to double check the clutch guys work.

Cheers Jim