Drivetrain Pressure plate to flywheel

Driver460sz · Oct 19, 2020

157 tooth RAM flywheel bolted on to my 351w. The flywheel seems to have two sets of bolt holes. One set seems to sit into the flywheel. The other holes are more flush. My ARP bolts seem to fit nicely in the recesses holes but not so much on the flush ones. While putting on a Mcloed clutch the flush holes lined up and not the recessed ones. So, I went with the holes that lined up but didn't seem to fit as well. Got everything snuggled up but when I hit the bolts with my torque wrench then seemed to do the aluminum spin. Without wanting to fully strip out the holes I left it as is.....maybe 12-15 lbs.

Ughhhhhh.....what next? Recap and try new bolts, helicoil, just dump the flywheel and get a new one or am I ok? Not near the 30 lbs recommended.

So not the thing I want to F with as the motor is supposed to go into the car this weekend.

Anyone know what I am talking about with the two sets of holes? And what is the advice out there.

Thanks

Exrace89GT · Oct 19, 2020

If I’m not mistaken one set of holes are metric and the other set are regular. My Ford Racing flywheel is like that. Mine also has holes for dowel pins to locate the pressure plate.

08GT500 · Oct 20, 2020

Hi,
I’d not take the chance of using it as is, nor retapping the same size, Heli Coil, as threads are not deep enough to support the torque reliably.
High risk of it coming apart, many times they‘ll disintegrate, sending parts everywhere, hurting the Trans, Bell, possibly Motor, but most importantly- Someone.
Options are:
1) Acquiring another Flywheel.
2) Bring it to a Machine Shop, have them clamp it to a rotary table on a Mill, indicate centerline, drill & Tap another bolt circle and Dowel holes an inch or so over for your Pressure Plate.
3) Drill & Tap in a steel thread insert which has the original thread size and pitch, in place permanently with Loctite Cylindrical locking compound. Again, a Machine Shop job
Only (3) ways to do this without a Mill.
5) (if clearance allows) run a thin G-8 Nut with Loctite above a hardened washer on the backside.. Dowel pins must be locked in place to bear the shear load.
6) If you can make the other pattern work for you, and the Dowel pins line up, that’s an option.
7) A bit thin for a Helicoil unless you could run a G-8 Nut & Washer on the backside to lock it up.. Any room to?
8) Go larger on the thread size where that counterbore becomes full threads. Then you’d be opening up the holes on the PP slightly.
As long as the PP’s alignment dowels are lined up, it’ll be OK.
If offcenter at all it’ll create vibration.
Shoulder bolts are used in partially counterbored holes as dowels on certain Clutch styles, they do also grab fully threaded holes.
Best of luck!
John

General karthief · Oct 20, 2020

Be safe, have a machine shop look at it, call the manufacturer or the place you got it from, they my work with you getting a replacement, I wouldn't install without expert advice or replacement.
I can picture it malfunctioning and I kinda like my feet, they been hanging around the end of my legs for a while.

Driver460sz · Oct 20, 2020

So, seeing I set my mind to just getting a new flywheel I decided to pop over to the local hardware store. I grabbed some grade 8 bolts, a little longer for fun. Pulled the current setup apart, cleared the holes and added some red and retired. The new bolts locked in, feeling the same as the old ones but kept digging. Once the pressure plate snuggled against the flywheel it torqued right up. Going to be honest....my thought is, because it was aluminum and felt soft, I felt I stripped it. That being said... I think I am all good. Flush plate to flywheel and sitting at 35 lbs of pressure.

Me thinks I am good....yeah?
.....

General karthief · Oct 20, 2020

Sounds good, what was the difference in bolt length?

Driver460sz · Oct 21, 2020

General karthief said:
Sounds good, what was the difference in bolt length?

1/4 inch. But the ARP had a washer and the new one does not but has a flange. The flywheel certainly had more thread left in the hole with the shorter bolt on it. Which is why I gave a slightly longer one a try.

08GT500 · Oct 21, 2020

Driver460sz said:
So, seeing I set my mind to just getting a new flywheel I decided to pop over to the local hardware store. I grabbed some grade 8 bolts, a little longer for fun. Pulled the current setup apart, cleared the holes and added some red and retired. The new bolts locked in, feeling the same as the old ones but kept digging. Once the pressure plate snuggled against the flywheel it torqued right up. Going to be honest....my thought is, because it was aluminum and felt soft, I felt I stripped it. That being said... I think I am all good. Flush plate to flywheel and sitting at 35 lbs of pressure.

Me thinks I am good....yeah?
.....

Driver460sz said:
1/4 inch. But the ARP had a washer and the new one does not but has a flange. The flywheel certainly had more thread left in the hole with the shorter bolt on it. Which is why I gave a slightly longer one a try.

Hi,
Only airing on the side of caution here, not knocking things.
The ARP’s were too short to grab all of the Flywheels threads....1/4”!
So, certain no threads began to strip with the shorter bolts? Aluminum threads crack when they begin to strip, brittle. No clue why they don’t Helicoil.
If you cleaned, saw no chips, didn’t chase threads and spun bolt(s) in by hand easily, threads are likely fine.
With good threads, PP to Flywheel Dowel pins in place, grade 8 flange bolts torqued to spec’s using Loctite on 7-9 good threads (5/16”-18), that’ll work, providing the Flywheel’s billet, Clutch isn’t rated for 800Ft/Lbs, motor’s not a 600HP+ build running slicks. lol.
Shoulder bolts into the tight tolerance, counterbored holes is recommended as it adds shear strength much like a Dowel, keeps PP mounting holes against a flat hardened surface. Threads can be cut into,or may cut into PP’s holes. Dowels work, but a combined effort to keep the PP from twisting, lifting.
Running Flywheel studs (below) is best for counterbored holes. Stud shoulder bottoms out once the Flywheel threads begin, solid flat surface for the PP mounting holes to to contact.
It adds both Tensile and shear strength, protects threads from bolt shift damage.
G-8 fasteners are 150,000lb Tensile, ARP’s Street Performance fasteners are rated 180,000lb Tensile, G-12’s are run for ARP’s Pro series (200,000lbs).
ARP‘s G-12 Flywheel Stud/12PT Nut Kit.

Best of luck!
-John

Drivetrain Pressure plate to flywheel

Driver460sz

Exrace89GT

Member

08GT500

General karthief

wonder how much it would cost to ship you a pair

Driver460sz

General karthief

wonder how much it would cost to ship you a pair

Driver460sz

08GT500

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Drivetrain Pressure plate to flywheel

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wonder how much it would cost to ship you a pair

wonder how much it would cost to ship you a pair

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