TKO600 clutch

[RICK LAKE]

elmariachi Jim I missed the Dallas thing unless it was Football. Anyway, Couple of things here are not quite right
Pressure plate bolts rely on the first 3-4 thread for 90% of there holding powers on a clutch pressure plate to flywheel.
I have run an iron flywheel (40#) for 3 years and now run an Aluminium one. There are helicoils in the Summit one I have. Yours may also have them or a timesert for the clamping power needed. I have not had a pressure plate bolt come loose in any of my cars or the Vettes, GTO's, or trucks I have worked on in the last 10+ years. I allways used Loctite for flywheel and pressure plate bolts, RED not blue. You are worried about your bolts in your clutch, you should see the small ones now being used in the new stuff. 8 & 10MM heads on a 1/4" -5/16's thread.
If you are running a RACE clutch with a 3,800# and up clamping load and up I could see the issue with longer bolts. Most Cobras are running a 2,800# to 3,200# on the street. If you want more holding power of a clutch, multi disc is the way we are going.
I use the washer on my bolts and have no problem. I the old days there was a steel ring that the bolts of the flywheel went through to not gall the surface of the flywheel. I never found loose bolts on one of these motors with 20-50 thousand HARD miles.
There is alot of heat and expansion going on in the bell housing, also alot of stress on the pressure plate bolts. Having washer washers spreads out the load bearing on the heads of the bolts, they may even absorb some of the loading and unloading pressures. I believe in ARP bolts, nuts, washers, and other fasteners. I have used them on motors for more than 30+ years. I have broken everything in a block but have yet to have a bolt break of theirs cause the main failure.
Jim go with a longer bolt if you want, just make 100% sure that the other end doesn't hit the block, or block plate in a full 360 degree rotation. I have seen this happen a couple of times. Rick L

[undy]

The rule-of-thumb for thread contact is, 1.5 x diameter of bolt/stud. This is a generality, variables like hardness, materials, threaded hole depth etc impact on it. Bottom line, if you follow this you'll never come up "short".

That was one of the first concepts I learned in the Navy's Machinist Mate "A" school back in 1970..

[RodgerH]

Originally Posted by undy

The rule-of-thumb for thread contact is, 1.5 x diameter of bolt/stud. This is a generality, variables like hardness, materials, threaded hole depth etc impact on it. Bottom line, if you follow this you'll never come up "short".

That was one of the first concepts I learned in the Navy's Machinist Mate "A" school back in 1970..

Undy, if you had read this thread from the beginning (at least from the point where Tom Kirkham brought up the concern with the bolts), you would realize that you are repeating what has already been stated...and that this is exactly the concern.

As previously discussed in this thread, with the ARP fasteners you very well may NOT have this thread depth. (Actually, ARP said 1.5 X dia. MINIMUM, and RECOMMENDED 2 X dia. when threading into aluminum.)

ARP has stated their pressure plate bolt sets are intended ONLY for OEM replacement and could very well NOT have adequate shoulder or thread length for aftermarket aluminum flywheels.

You guys jumping in at the end of this discussion need to read this thread from the beginning to get the whole story.

As far as Rick's statement: "Jim go with a longer bolt if you want, just make 100% sure that the other end doesn't hit the block, or block plate in a full 360 degree rotation." This too has already been discussed. Go back and read the entire thread. I did this and ARP explained in detail why that was the WRONG thing to do...unless you do some careful measurement concerning the shoulder length (and no, ARP says you should NOT use a shoulderless bolt....read their reason in my posts in this thread.)

I retired from a career as an engineer in the maintenance department of a major chemical production facilty where I learned the devil is hidden in the details. You may not realize the weakness of a component (or worst case, the failure thereof) until you look at it in the smallest detail. I've also been a gearhead/semi-pro racer all of my adult life. My hobby and my career complimented each other and each helped me to be better at the other.

OK....I'm off the soapbox. Maybe we have taken this to a greater level of detail and concern than necessary. Maybe just using a suitable bolt (obviously Grade 8 minimum) of a length to obtain adequate thread engagement is all that's really important. Maybe the shoulder isn't even necessary. Maybe the advice from ARP is more detailed than we need to be concerned about.

Rodger

[patrickt]

Originally Posted by RodgerH

Maybe we have taken this to a greater level of detail and concern than necessary.

In the words of the great George Anderson at Gessford, "That's how the Ford engineers designed it, and in 25+ years they never saw fit to change it. That's good enough for me."

[patrickt]

Originally Posted by RICK LAKE

You are worried about your bolts in your clutch, you should see the small ones now being used in the new stuff. 8 & 10MM heads on a 1/4" -5/16's thread. ... I use the washer on my bolts and have no problem. In the old days there was a steel ring that the bolts of the flywheel went through to not gall the surface of the flywheel. I never found loose bolts on one of these motors with 20-50 thousand HARD miles. ... I believe in ARP bolts, nuts, washers, and other fasteners. I have used them on motors for more than 30+ years.

If anything, Rick tends to fall on the "alarmist" end of the mechanic's spectrum. For him to allay our fears of the ARP bolts speaks volumes. Just periodically stick a torque wrench in the fork hole and make sure they're snug -- that's all you need to do. And if you've been running non-shouldered Grade 8 bolts without a hitch for a couple of thousand miles, I don't think you need to change them out either. Rick is great -- Rick is my hero -- I love Rick.