67 390 w/toploader min Flywheel spec

[bkdunha]

After inspecting the flywheel during the upgrades to my 67 390 I noticed some (hopefully small) cracks in the flywheel.  I would like to try and resurface the piece.  Does anyone have the minimum thickness spec for a 67 Mustang 390 flywheel?  Thus far, my research indicates a blind hole on the disc surface to indicate the min thickness.  I do not have the flywheel with me to verify right now.

[ScotiaFE]

I would retire the stock cast wheel. It has done it's duty.
Time for a steel wheel.
Not much cost wise and much safer. jmo

[fairlaniac]

I realize this is rather old but the question still remains. What is the minimum thickness for a cast FE flywheel? I'm sorting through parts and have a couple.

Thanks!

[Tunnelwedge]

Interesting. I have a couple also. Sorting also.
The blue one is 1.002" at the thickest spot.
The black one is 0.869" at the thickest spot.
I still think a steel wheel is safer.

[fairlaniac]

Interesting. I have a couple also. Sorting also.
The blue one is 1.002" at the thickest spot.
The black one is 0.869" at the thickest spot.
I still think a steel wheel is safer.

And I use steel flywheels my self but someone running a 4800 rpm 352 truck and on a budget may find use? I still cannot find a minimum thickness anywhere and I'll assume by the total internet's lack of info on this, the number doesn't exist?

[pbf777]

     I realize that this posting started a number of years ago, but as being resurrected and as the question of "minimum thickness" never was established then, and now being asked again, I would put forth this:

     The reason one can not find a printed specification from the O.E.M. on this subject is that there never was an official number ever presented.  Rather, the O.E.M.'s statement was that if the surface of the used flywheel was deemed "not serviceable" then it was to be "replaced" (new one) with no mention of "resurfacing".   

     If one considers the manor of function involved with the flywheel, the realization that the original unit may apparently be in a damaged state, and the fact that the potential repair operation which results in a reconfiguration of the flywheel's original engineering, all this resulting in the fact that the "repaired" item has deviated from that of the intentions of the O.E.M. into unknown territory, then it becomes obvious why the manufacture would take the position of "just replace it" with a known commodity.   

     Scott. 

[galaxiex]

I've been in the transmission repair industry for 45 years.
We "used to" resurface flywheels on clutch jobs.
Stock replacement, not high performance.
We would send the flywheel to a shop that had a surface grinder specifically made for surfacing flywheels.
Presumably the shop had specs for how much to "cut" and would sometimes tell us that the flywheel was beyond limits.

I "think" the max cut was 0.060" to 0.080" or so. Maybe as much as 0.100" if it was really beefy to start with.
If it took more than that to clean it up, the flywheel was junk and we got a new one.

This all more-or-less ended in the mid to late 90's as many stock replacement clutch kits then simply came with a new flywheel.


Edit: The shop grinding the flywheel would always try to take the smallest cut possible to clean it up.
They would tell us how much they cut so we could shim appropriately.
Some clutch kits came with flywheel shims to compensate for the cut on the flywheel.
There was/is a company that had/has flywheel shims for popular makes and models.

[pbf777]

     We are a machine shop, and do have a dedicated "Flywheel Grinder" (Winona), and do still grind flywheels; but there is not any stated or printed reference literature available to be utilized as a guide available which would outline any "go no-go" dimensions for these light vehicle flywheels.  It's all a matter of experience when the machine shop advises the customer that it's either a good idea or not, in the resurfacing of the flywheel face.   

      And your not going to be cutting sums anything near those numbers, if only because you'd take all day to do it, and you'd use up to much of the consumables to make it profitable.  Rather, if one really needed to (and were it even possible/advisable  ), one would chuck the flywheel in a lathe first, cut it down to size and then place it in the flywheel grinder to finish.   

      Scott.

     
     

[Urgefor]

Rather, if one really needed to (and were it even possible/advisable  ), one would chuck the flywheel in a lathe first, cut it down to size and then place it in the flywheel grinder to finish.   

I have done that exact thing using a brake lathe then sending the flywheel to the local machine shop to be finished.  Customer was happy to save some $$ on the clutch replacement in his well used 4 cylinder daily driver.

[galaxiex]

     We are a machine shop, and do have a dedicated "Flywheel Grinder" (Winona), and do still grind flywheels; but there is not any stated or printed reference literature available to be utilized as a guide available which would outline any "go no-go" dimensions for these light vehicle flywheels.  It's all a matter of experience when the machine shop advises the customer that it's either a good idea or not, in the resurfacing of the flywheel face.   

      And your not going to be cutting sums anything near those numbers, if only because you'd take all day to do it, and you'd use up to much of the consumables to make it profitable.  Rather, if one really needed to (and were it even possible/advisable  ), one would chuck the flywheel in a lathe first, cut it down to size and then place it in the flywheel grinder to finish.   

      Scott.

     
     

Thanks for that, I'm sure I was old guy remembering the numbers wrong,
and it's been quite a few years since we had any flywheels cut.

Come to think of it.... I seem to recall the guy that did our flywheel grinding would usually say they took
0.020" or 0.030" off to clean it up.

It could also be he did cut them on a lathe first.

[GerryP]

I've never seen a spec for flywheel thickness.  I suppose if it got too thin, it would be difficult to get an adequate adjustment on the clutch since that fine distance between the clutch fingers and the release bearing gets wider when the flywheel is cut.  So, I guess the clutch is done when the adjustment can't be reasonably achieved.

[pbf777]

        Actually, the adjustment function of most of these older mechanical clutch linkages will suffice within the possible resurfacing distance of the flywheels; the 'real' issue would be when the flywheels strength and heat absorption capacities are defeated to the point of flywheel failure!   

        Scott.

[BigBlueIron]

My experience is its not necessarily the thickness or lack there of that renders them junk its the clearance of the clutch disc hub to the flywheel bolts. 

[Tunnelwedge]

The finish on the flywheel is also very important.
If using an organic disc, Blanchard ground is good.
Iron or ceramic disc, precision ground is best.

The black one, I took a palm sander to it once and put it back in.
Took the green Fairlane to almost 150 MPH with a backyard 390.