Lucky Mod

[riotwarrior]

Took the flywheel back out of the truck last night, dad took it by a local retired machinist who doed small jobs for farmers at home, he's gonna mill 6 more holes in the flywheel halves for a total of 12- 3/8" bolts holding the halves together. Got some bolts from fastenal, Dad came home with 12 Grade 9, 3/8-16x2(no 24 tpi in stock) bolts and metal locking nuts. If it shears those off he will just have to buy a single mass kit.

My question..are they a full depth shouldered bolt? You can always remove the threading/cut off if too long!

 

[Old Blue]

I think the fact that you now have a more certain chance of a high quality bolt and some very accurately drilled (milled) holes will make all the difference, it sounds great. Remember, the flywheel bolts to the crank with (8) 3/8" coarse thread grade 8 partially threaded bolts, but if you check you will find those are installed with the coarse thread in the shear plane (joint.) That joint is stabilized with a concentric ring to keep it accurately centered, but those threads are taking the torque. I think the quality/match of the holes between the two mating surfaces, the quality of the bolt, the thread lock quality, and the bolt torque will go a long way here in this 2nd attempt! Good luck! Make sure there is nothing on the two main surfaces of that joint that could break down or give way and relieve the bolt torque over time, like rust, dirt, metal flecks or oils.

 

[franklin2]

Fine thread gold colored bolts from Ace hardware are holding my Lucky Mod together. Been going for 3 years now, noisy as ever.

 

[dsltech83]

Well, got the truck back together last night with 12 grade 9's in the fly wheel, so far has made it longer than the first attempt. Will let everyone know if we have another failure.

 

[bike-maker]

I used 7/16" NF bolts in mine. They have "Dorman" on the heads of them. Been holding for about 3 years and towing a 10k pound trailer fairly often.

 

[trj]

Just thought I'd post another failure. I am a machinist by trade and drilled the 6 holes for grade 8 bolts using new drills. The steel being drilled through is pretty hard. Harder than I expected in the material used even with coolant so keeping a sharp bit may be pretty important or reaming as suggested earlier. I stepped drill sizes up progressively then finished with the new drills. The bolts were 3/8x24 tpi and I used metal lock nuts with red locktight torqued to 35 lbs/ft. I also used longer bolts so I could cut them to get the un-threaded part nearly all the way through both parts and still get them torqued to get max. clamping force. The truck was sold shortly after and the new owner had a failure of the flywheel. I can't tell you whether there was abuse involved but even if there was there is the means to over design and I think if I ever did the mod again I would double the number of bolts. Very little cost is involved and it is a critical situation not easily accessed.

 

[hesutton]

Chase..

Any updates? How's your Dad's truck doing?



Heath

 

[dsltech83]

Heath,
Dad's truck is doing great. Not sure how many miles he's put on it but we've pulled a trailer a couple times with no problems. Rollover noise is annoying though.

 

[hesutton]

That's good news.

Thanks for the update man.


Heath

 

[Beads 93 idi]

What is this lucky mod yall speak of ????? I can't find it nowhere ....

 

[hesutton]

HERE YOU GO.

It's called the Lucky mod as Jim Williams (not been on OB in a while) came up with it. His handle is LUCKY_LARUE60 here.


Heath

 

[Agnem]

Just thought I'd post another failure. I am a machinist by trade and drilled the 6 holes for grade 8 bolts using new drills. The steel being drilled through is pretty hard. Harder than I expected in the material used even with coolant so keeping a sharp bit may be pretty important or reaming as suggested earlier. I stepped drill sizes up progressively then finished with the new drills. The bolts were 3/8x24 tpi and I used metal lock nuts with red locktight torqued to 35 lbs/ft. I also used longer bolts so I could cut them to get the un-threaded part nearly all the way through both parts and still get them torqued to get max. clamping force. The truck was sold shortly after and the new owner had a failure of the flywheel. I can't tell you whether there was abuse involved but even if there was there is the means to over design and I think if I ever did the mod again I would double the number of bolts. Very little cost is involved and it is a critical situation not easily accessed.

I don't know if it makes any difference or not, but I always coat the back of the bolt head with locktite also. I don't want either end moving!

So in reading through this thread, it looks like there were 3 people who reported lucky mod's in excess of 3 years sucess, as well as my own now going on 6 or 7 years. My advice to people is not to mess with the forumula (the OP used course thread bolts, and trj used longer bolts that he cut) and be diligent in the pursuit of quality.

 

[dsltech83]

Well, it's now been a year and a half plus on the lucky mod, not sure how many miles we've put on the truck but we haven't had a lick of trouble.

Chase