Howdy y'all!

Been researching the heck out of my clutch replacement project, I'm bound and determined to get it right this time! After inspecting the flywheel, it is obvious it needs replacement or resurfacing. It has already been resurfaced a few thousand miles ago, but something went terribly wrong, I can only speculate what that was, but it involves the clutch components. I've been looking on Summit and Jegs for flywheel compatible with my 1972 350 vette but the filters were acting weird, and I was having difficulty finding OE. So, I thought it may be better to use the one I have. A few things I am concerned about;

-- thickness, i'm confident mine has only been cut once, the thickness is a tad more than 1.2" which seems like it could easily tolerate being cut again. I have checked the clearance between the heads of the crankshaft bolts and the disk springs (made that mistake once before about 30 years ago on a 1st gen camaro).

--I've also read about problems with the pressure plate bolts bottoming out and not clamping the pressure plate, but that doesnt seem to apply here since they are through holes. But, when the pressure plate bolts are fully threaded in up to the shoulder, there is still about 1/4" before they would protrude out of the other side of the flywheel.

-- also there was discussions about the increase in throwout bearing travel before it contacts the pressure plate diaphragm fingers, but I don't understand why this would be, can't this be corrected for by adjusting the rod that attaches the brake pedal to the Z-bar? (I have quite a bit of adjustment left until I would be at the end)

-- something I noticed while inspecting the flywheel is that it has a very slight concave shape to it, that is it is ever so slightly dished out like a plate. I never expected this, but found reference to this being typical.

-- I dont see any stress cracks, but should I have it magnafluxed?

Anything else I should be concerned about? Does anyone have any suggestions of a compatible OE flywheel?

 

oops, that was the wrong picture, this is the flywheel

flywheel

 

also there was discussions about the increase in throwout bearing travel before it contacts the pressure plate diaphragm fingers, but I don't understand why this would be, can't this be corrected for by adjusting the rod that attaches the brake pedal to the Z-bar? (I have quite a bit of adjustment left until I would be at the end)

The issue is that surfacing a flywheel by what ever thousands will translate at the Z-bar will be significant more. To a point that there will be zero adjustment left on the adjustment arm. Usually after 2 or more re-surfacing. Two ways to repair this issue is to replace the clutch ball stud in the bell housing to a long one or replace the flywheel with one of the original material thickness.

 

Thanks PJO for the explanation, I understand now, it's not a 1:1 ratio (maybe aprox 1:5?) Hopefully I will have enough adjustment left after the resurface, but good to know the options. Of course I don't want to put it back together to find out, so maybe it is in my best interest to get the longer ball-stud if I do in fact have it resurfaced.

Adjusted like this had the throwout bearing just making contact with the pressure plate, which I know wasn't correct, but needed it this way to get the clutch mostly disengaged, and I think it still could have used a tad more travel for better disengagement. That is one of the problems I'm trying to correct. From my research, this is a common issue, one that I expect is going to be corrected by using a McLeod clutch kit. I had been using a Hays pressure plate with a Science Friction clutch (made by American Powertrain).

 

I had trouble with the plastic speedo gear on my 73 with manual tranny. The Corvette Service Shop removed the tranny and had it refurbished. Ernie Willcox said they only use LUK clutches and flywheels, because they have experienced problems with other brands. So that’s what I ordered. Not sure about resurfacing, but the service shop I use, is owned by one of the largest Classic Corvette Resellers, so they know what works and what doesn’t.

 

If its suspect just call McLeod and order one that has tthe weight you want, they sell a bunch of different weights for GM motors. Are you running a 153 tooth or 168 tooth?
what weight would you like?
Heres 25 results from summit with 10.5 or 11 inch flywheels and 153 or 168 teeth, 2 piece seal and internal balance
https://www.summitracing.com/search/...tyle%3a2-piece

 

Heres some from Mcleod searching a 72 vette

nodular iron
https://www.mcleodracing.com/nodular...-1972-base/p19

steel. these list the weights
https://www.mcleodracing.com/steel-f...-1972-base/p20

 

Thanks for the info Eliredandblack. That does build my confidence in using LUK components. I'm bringing the flywheel that I have in for resurfacing today, and will see what the machinist has to say about if he thinks I should reuse it or not.

 

Thanks for the info and links Rescue Rogers. I'm not sure about the tooth count, but am quite sure it is the stock flywheel for a 1972 350. I'm bringing the one I have to the machine shop today, and will see what they advise. I suspect it will be fine to use it once it has been resurfaced......

 

they don't take much off resurfacing flywheels. if they take 10 thousandths off, which they won't and the z bar is a 5 to 1 leverage reduction, the pedal travel will drop by .050 inch. 1/20th of an inch.

 

Thanks derekderek! I figured it would be insignificant with such a small change in overall thickness from resurfacing. I had the flywheel cut today, and 8/1000s was removed, so I should have plenty of adjustment left.

 

I got the original flywheel cut today, and will be using it. I asked about the flatness and if it is supposed to have a very slight dished out nature to it and the machinist said that is due to the curvature of the grinding wheel and is normal.

 

when you put it back on, go get or borrow a dial indicator and make sure it is running true. you can also bolt a piece of coat hanger to the block or head and fashion it as a pointer about 20 or 30 thousandths from flywheel surface and crank the starter and eyeball it, but the dial is much easier to see.

 

Great advice! I actually just bought a dial indicator and magnetic base yesterday. I'm planning to use it as you said and also for checking the bellhousing offset.

Thanks!

 

Do you have a muncie or a 5 speed. Dialing the offset doesnt matter as much on a muncie due to the play built into those bearing cases. A 5 speed on the other hand has to be less than .004 total offset. They use cone bearings which have to be almost perfect

 

Yup, it is a Tremec 5 speed. I did measure it before I initially installed it and it was within tolerances. But for good measure, I will do it again.

 

So I did as derekderek suggested. I measured almost .008" run out (I think run out is the correct term), the measurements were aprox; 0 @ 0 degrees, 3 @ 90 degrees, 8 at 180 degrees, 6 at 270 degrees. I did the test more than once with very similar results.


I would have thought the machine shop would have discovered if the flywheel was warped while machining it......
I made sure the flywheel was seated on the crankshaft really well, and torqued it down evenly and tightly.
I was gonna try to measure the run out on the crankshaft hub, so removed the flywheel, I setup the gauge and started rotating, and then all of a sudden there was .020 change in the reading, when I looked closer it looks like some grinding was done on the end of the crankshaft. Could it be that it was dropped by the machine shop, and they tried to dress up the damage, or maybe this is how they balance it? It just seems kinda odd....

 

the part that matters is the flange where the 6 bolt holes are. clean up the edges with a file. a burr could cause it to not sit flat. then also check runout at the inner and outer edge of the machined surface.

 

I'm not sure where you are suggesting to test run out. I don't think I will be able to do it on the flange.

 

I measured .001 change with this test.