Clutch PP Torque

[Railroad]

I am getting ready to put the clutch pressure plate on my Gen I Coyote engine with Ford steel flywheel. The tq specs I am finding say 34 ft lbs plus 60*.
That seems rather tight to me. I confirmed I was not confusing in lbs for ft lbs.
The flywheel to crank was 14 ft lbs plus 60*.
I plan on checking with Mike Forte, but thought I would post here, also.
Thanks,

[edwardb]

Multiple references, including Ford publications, all say the same thing.

Tighten the pressure plate bolts in 2 stages in a star pattern.
Stage 1: Tighten to 47 Nm (35 lb-ft).
Stage 2: Tighten an additional 60 degrees.

Same idea for the flywheel. But 177 lb-in + 60 deg.

With these kinds of settings, likely are torque-to-yield bolts. I would make sure in both cases to use brand new bolts.

[Railroad]

Thanks edwardb. All new bolts.

[CraigS]

That seems WAY off to me. Most PP bolts are 5/16 right? and 'maybe' 3/8? See this chart
https://www.boltdepot.com/fastener-information/bolts/US-Recommended-Torque.aspx
A G8 fine thread is 37# and no extra 60 degrees. and a 5/16 G8 is just 20#. Good luck.

[Railroad]

Without checking, I think these are 10 mm. I cannot find any other tq specs for this part on this engine.

[CraigS]

metric tq chart
https://www.fastenal.com/content/feds/pdf/Torque-Tension%20Chart%20for%20Metric%20Fasteners.pdf

[edwardb]

Multiple references, including Ford publications, all say the same thing.

Tighten the pressure plate bolts in 2 stages in a star pattern.
Stage 1: Tighten to 47 Nm (35 lb-ft).
Stage 2: Tighten an additional 60 degrees.

Same idea for the flywheel. But 177 lb-in + 60 deg.

With these kinds of settings, likely are torque-to-yield bolts. I would make sure in both cases to use brand new bolts.

Nice theoretical debate. But it needs to be with the Ford engineers who established these settings. My previous response was a cut and paste from Ford references, as stated. More details:

Pressure plate bolts (and dowels): M-6397-B46, Thread Size:10mm x 1.50. https://performanceparts.ford.com/part/M-6397-B46. Instructions: https://performanceparts.ford.com/download/instructionsheets/FordInstShtM-6397-B46.pdf. Note they also confirm they’re torque-to-yield bolts.

Flywheel bolts: M-6379-C, Thread Size:10mm. https://performanceparts.ford.com/part/M-6379-C.

[Railroad]

Well now I have a spec of 35 lb/ft and 46 lb/ft then plus 60*?
Sending a message to Forte.

[edwardb]

Well now I have a spec of 35 lb/ft and 46 lb/ft then plus 60*?
Sending a message to Forte.

Oops. You're right. I didn't notice they were different. Let us know what you find out. I don't remember what I did on #8674, other than it's been fine now in its second driving season.

[Railroad]

Well, Ford Tech was emphatic, 46 lb/ft plus 60* is the correct torque for the clutch pressure plate.
The bolt strength is 10.9, just hoping the threads can stand the tq.

[Railroad]

Finally got back to the barn. After putting in the dowel pins, that is another story, I checked for paint marks on the FW and PP to align. Nothing there, so any of the 6 bolt holes on the FW. Torqued the PP down to 45 lb/ft in one turn increments using a star pattern. I marked the left from the top bolt head side with a marker and a mark on the PP where the flat needed to rotate to. I used the bolt head flat to give me the 60* increment. The bolts pulled down good and had no feel of stripping. As I tightened each bolt I would back the tq wrench setting down from 70 lb/ft till it would click at the final position. That probably does not make any sense, but the tq to get 60* from 45 lb/ft ended up being 57 lb/ft. I rechecked all 6 bolts and they clicked at 57 just before they wanted to move.
Short story, the Ford print out is OK 46 lb/ft then tighten 60*.
Now to get the clutch fork pivot bolt the right height. I will do some searching and see what I can find.
Using the Forte supplied parts, Tremec bellhousing.

[Mark Reynolds]

For the record Mustang 5.0 pressure plate screws are 8mm (not 5/16") so yes they are smaller than the Coyote.

[Railroad]

10 mm

[initiator]

The actual torque needed to reach 60 degrees will vary depending on how well lubed the threads and underside of the bolt head are. Don't know if you measured the exact torque needed so you wouldn't have to measure 60 degrees next time, but I wouldn't take that short cut.

Ideally, you'd calculate bolt preload by measuring bolt stretch for a torque-to-yield installation, but that's not possible for blind fasteners. So 60 degrees is the next best way to get a fairly precise stretch based on the thread pitch.

[Railroad]

The actual torque needed to reach 60 degrees will vary depending on how well lubed the threads and underside of the bolt head are. Don't know if you measured the exact torque needed so you wouldn't have to measure 60 degrees next time, but I wouldn't take that short cut.

Ideally, you'd calculate bolt preload by measuring bolt stretch for a torque-to-yield installation, but that's not possible for blind fasteners. So 60 degrees is the next best way to get a fairly precise stretch based on the thread pitch.

The bolts have a flat washer under the head and the threads are treated with factory locktite, so lube would not seem compatible. The hole in the flywheel is not a blind hole, evidenced by the bolt slightly showing on the block side.
I tried to learn the ending tq out of inquisitiveness. I was having too much fun holding flywheel with a bellhousing bolt marking the bolt and pressure plate and tightening the bolt. Add to that, I would adjust the wrench down until it clicked at the 60* mark.

I am going have to trust Ford on the proper tq and rotation for bolt stretch.
I do not recall this being discussed earlier, might have missed it.

Another area of greater concern is watching for the 4.6 flywheel bolts, they are the right diameter and thread, but do not engage enough threads. The easiest way to identify them, the 4.6 has cross grooves cut in the head of the bolt, the Coyote 5.0 are solid head and LONGER.

Thanks for the reply. Your car sounds a lot like mine. I need to update my accessories and get some more work done. Hopefully, I will have some help hanging the trans onto the engine this week. Getting close to having the complete drive line installed.