Flywheel bolts mininum thread engagement

[Merica906]

Hi I have a 1994 ford ranger 3.0 and I'm replacing the clutch, flywheel and slave cylinder and I noticed on the new flywheel in the center where it bolts on to crankcase is about .25 in thicker then the old one and now the bolts only engage the threads about a .25 of a inch to the flywheel. My question is with some orange loc tite would that be a safe amount of threads.

 

[pjtoledo]

nope.
I don't know the exact spec on engagement, would try for at least 10 full threads.

EDIT: after a quick search found this

crankshaft bolt thread engagement - Search

 

[slater50]

Find a flywheel with same thickness flange, dont play games....

 

[alwaysFlOoReD]

If its 1/4" thicker, then you need 1/4" longer bolts...

 

[Blmpkn]

I *believe* I remember reading years back that NASA's regs for thread engagement were to have the same amount of threads grab as the fasteners diameter... So a bolt with a 1/2" shank wants/needs 1/2" thread engagement..

I read that on the Internet though so

 

[Curious Hound]

Get longer bolts. As mentioned, minimum of one bolt diameter of engagement. So, if they are 1/2" bolts, they need to thread into the crankshaft at least 1/2". This is general mechanical standard in industry, not just NASA.

And don't bolt it to the crankcase. That doesnt rotate very well.

 

[slater50]

This bolts dont have a very common thread pitch, the price you pay for bolts, you can easily return the flywheel & get one that is correct,
If the flange is thicker, maybe the offset is also different....
Did you lay them side by side to see overall height?

The youre going to have the guys come on here & tell me, the slave cylinder will compensate for that....
Do it right & dont Micky mouse with shit parts, not fun doing a job twice....

 

[Rick W]

Not my expertise, but a couple thoughts. Does the back of the old flywheel and the back of the new flywheel (the opposite side from where the clutch disc rubs), are they both the same? Check it with a straight edge and such.

Also, a poor man’s way to check thickness: straighten out a paper clip, and put a tiny little L on the end of it, maybe 1/8 of an inch. Then you can insert it in the bolt hole, pull it back til it catches, and hold that spot with your fingernail while you remove it. Then you can stick it in the other flywheel and see if it’s the same thickness.

Finally, if you do go with longer bolts, make sure you get the same “grade” bolt. Grade meaning harness. If it’s a hex head bolt, the hardness is often indicated by a series of marks on top of the bolt. “-“ marks radiating out from the center. If it’s an allen head or a torx, I’m not sure how you can tell. There’s a lot more to bolt strength than simply length, diameter, and thread count. If you put “soft” bolts in there….

And I think a lot of these guys are driving at the same point, but they didn’t say it the same way: safety first. Don’t try to do something cool or try to save a few pennies, and end up with a clutch disc up your butt! It’s not something you want to fool around with. I know a guy with seven toes because the clutch assembly came up through the floor, but that was on a hot rod. But there’s still an awful lot of energy in that spot in the vehicle.

My two cents, as always, I hope it helps

 

[slater50]

totally agree with bolt grade & not like theres markings on a specialty bolt like that, grade 8 isnt always the answer...
Vibrations, violence from combustions, pressure from the clutch, why play games, get the right parts...
Im sure we wont even hear back from the op...

 

[Merica906]

I got a new flywheel coming Thursday that should be the same thickness as the old the flywheel and I should be able to use the old bolts. The thicker bolt flange one I was trying to install I got from the previous owner of the truck thinking it was the right one for my truck

 

[Rick W]

I got a new flywheel coming Thursday that should be the same thickness as the old the flywheel and I should be able to use the old bolts. The thicker bolt flange one I was trying to install I got from the previous owner of the truck thinking it was the right one for my truck

Great! Sounds like a plan!

Now everyone can jump on you to buy a new set of bolts. It’s a few pennies for security in a place where there’s a ton of energy and torque.

And forgive me, I don’t know you or your experience, and I’d rather say some things for safety first, rather than assume. Make sure you torque the bolts in the correct pattern, and in the correct sequence, to the correct tension. And I’ll bet that flywheel requires a particular grade of thread lock. I’m sure some of these guys will know those things.

As always, my two cents. If you saw some of my junk, you’d jump up on the table and say “who the hell is this guy to tell me how to do stuff? Look at that crazy stuff he put together.” Do as I say, not as I do , as the saying goes.

And if you get all of that done, and you do it right, we’ll find something else to hound you about.

Welcome aboard again!

 

[slater50]

were you able to extract the pilot bearing from the back of the crank.
Under no circumstance do you want to re-use it....
Very common to blow apart from wear & tear, even if it looks good now.
Dont re-use the slave cylinder either....