Snapping Flywheel Bolts...?

[AcIdBuRn02ZTS]

Hey alls...

I'm in the process of buying a few engines from a local and have a question...

The main engine i'm looking at was just rebuilt... bored .020 & fitted with npr pistons... has a properly installed mhg with arp studs...

has roughly 4500miles on it but the po ran into a problem... it started snapping flywheel bolts. He tried different flywheels... different harmonic balancers... the only thing he didnt try was a different clutch... and he is thinking that the problem is coming from not having the rotating assembly balanced... however... with .020 oem replacement pistons... would it be far enough out to be snapping flywheel bolts? He said with solid motor mounts... he didnt feel much vibration and the car ran great and pulled strong at 8-10psi....

so... is the problem in the lack of balancing the rotating assembly or could it be something else?

Thanks
-AcId-

 

[ians13]

Hey alls...

I'm in the process of buying a few engines from a local and have a question...

The main engine i'm looking at was just rebuilt... bored .020 & fitted with npr pistons... has a properly installed mhg with arp studs...

has roughly 4500miles on it but the po ran into a problem... it started snapping flywheel bolts. He tried different flywheels... different harmonic balancers... the only thing he didnt try was a different clutch... and he is thinking that the problem is coming from not having the rotating assembly balanced... however... with .020 oem replacement pistons... would it be far enough out to be snapping flywheel bolts? He said with solid motor mounts... he didnt feel much vibration and the car ran great and pulled strong at 8-10psi....

so... is the problem in the lack of balancing the rotating assembly or could it be something else?

Thanks
-AcId-

What type of bolts are snapping factory bolts, new or used bolts.
Try some apr bolts and make sure the bolt holes in the fly wheel are not worn out bigger from it moving around. Too much movement of the flywheel will cause vibrations and brake bolts

 

[AcIdBuRn02ZTS]

I believe he tried stock and ARPs also... several flywheels... but I'll have to get with him and see what all he tried

-AcId-

 

[ians13]

I believe he tried stock and ARPs also... several flywheels... but I'll have to get with him and see what all he tried

-AcId-

The problem if not the flywheel, could be caused by the bolts coming lose. One lose bolt can cause uneven load on the other bolts, make sure the torque is correct and it might help to use light thread lock

 

[AcIdBuRn02ZTS]

so you dont believe it could be an internal problem?

-AcId-

 

[GrimJack]

This has happened before, but not before some pretty high power numbers - roughly 700 foot pounds of torque coming out of the engine when Duane's failed, as I recall.

He switched to ARP hardware and was fine for a while, but switched to an auto soon after.

There are a bunch of reasons why this could happen, though. Incorrect torque on the bolts, problems with the threads on the crank, bad balance on several different parts, crank / flywheel face not absolutely flat, wrong threadlocker... just the ones that I can think of off the top of my head.

 

[AcIdBuRn02ZTS]

so would you suggest I pull it apart and have the guts balanced? I have several cranks so I could swap the crank out for good measure... and i'll be running it as an auto... he was using a 5spd...

hmmm....

-AcId-

 

[ForcedTorque]

A new crank and a balance job would give you peace of mind. If you have the means at hand, I would suggest you do that. It would rule out balance, and also rule out the threads in the crank.

 

[upgradedsupra]

This has happened before, but not before some pretty high power numbers - roughly 700 foot pounds of torque coming out of the engine when Duane's failed, as I recall.

He switched to ARP hardware and was fine for a while, but switched to an auto soon after.

There are a bunch of reasons why this could happen, though. Incorrect torque on the bolts, problems with the threads on the crank, bad balance on several different parts, crank / flywheel face not absolutely flat, wrong threadlocker... just the ones that I can think of off the top of my head.

Yes, was right at 7. What a mess that was. lol

Duane

 

[Poodles]

ARP hardware, red thread locker, proper torque, and safety wire. Shouldn't come loose after that. Can also get something like what driftmotion makes for the JZ's

 

[AcIdBuRn02ZTS]

I talked to the original owner... he said he tried and broke New OEM bolts, hardware store bolts... and ARP bolts all torqued to proper spec and they where pretty well one right after the other... It wont hold together....

I'll have the engine in my possession here soon so I'm wondering if I should just pull it apart and see if its an internal problem... I just wouldnt think that a .020 size difference would throw off balance that much to a point of breaking bolts like that...

-AcId-

 

[ians13]

A bent crank shaft would cause vibration; the right frequency could cause the bolts to come lose, damn you going to have to pull this thing apart and have the crank checked. Might be in your best interest to have the whole assembly checked.

 

[AcIdBuRn02ZTS]

Well... I'll have a few cranks... im getting a total of 4 engines.... two complete (the rebuilt one that is breaking flywheel bolts and one with a bhg) and two short blocks... a rebuilt cyl head, and a bunch of spare parts... so I'm sure I can get it together without too much hassle... I may just pull the one with a bhg apart and see what it looks like... if its in decent shape... i may just hone/ring it with new bearings, oil pump, etc.. and the mhg and studs from the other motor and go with it....

Ive got options... I just didnt know what could cause this besides an internal problem...

-AcId-