10 replies to this topic

[limby2000]

I've put my crank in my newly machined 1098 block, fitted mains and torqued up no problem. Fitted pistons and rods, started to progressively torque the con-rods and turning crank for tightness , until I found too tight to turn by hand. After a bit of head scratching I realised i,d overtorqued by about 15-20 ft llb. I have another set of used bolts (old) style with locking tabs which originally came with these rods (flange bolts on at moment). Also will the new bearing shells be ok or are they crushed . Your opinion please.

[Cooperman]

Bearing shells will be fine, but the bolts & nuts will have been taken towards their elastic limit. Buy & fit new bolts & nuts and torque them correctly and you'll be OK.

20 lb.ft over recommended is approaching a 50% over-torque from nominal.

Edited by Cooperman, 28 September 2015 - 06:03 PM.

[sonikk4]

Personally i would change the bolts. Been down the road of over torquing small end bolts, one sheared so i changed the lot. (Not a mini by the way) Cannot say what the actual figure was but enough to shear at least one.

[carbon]

Limby, you say that once the rod bolts had been overtorqued that the crank ended up too stiff to turn? I would look very carefully at the rods in case they have distorted. Should not be the case, but the rods are threaded for the big-end bolts.

 

Then I would suggest using Plastigage on all 4 bigends, and torque down all of the rod bolts to correct figure. Use this to check big-end clearances are all within limits.

[limby2000]

I've checked my torque wrench, it was set to 55 ft llb, however it never made it to the (click) sound as I was progressivaly moving from bolt to bolt I was aware that something was wrong and stopped, so did,nt actually make it to 55.

[gazza82]

Could have made it to 54 though :-(

[Spider]

Bin the Bolts, be sure they never get used anywhere for anything.

 

Limby, you say that once the rod bolts had been overtorqued that the crank ended up too stiff to turn? I would look very carefully at the rods in case they have distorted. Should not be the case, but the rods are threaded for the big-end bolts.

 

Then I would suggest using Plastigage on all 4 bigends, and torque down all of the rod bolts to correct figure. Use this to check big-end clearances are all within limits.

 

As Carbon has said, this does sound peculiar, unless you torqued them up to like 100's of ft / lb this alone shouldn't cause the crank to lock.

 

Have a look at the bearing shells for witness marks, if you see any, then you'll not only need new shells but you'll need to have your rods closed and honed to reshape and resize them.

[Dusky]

Overtorqued bigend bolts is an annagram of 'replace' ;- )

[limby2000]

Ok, so will change big end bolts and depending on condition of big end shell (crush marks or scouring), may change them too.

[AndyR]

Just be glad they weren't a set of ARP bolts.  I got interrupted for a second and ended up setting Nm on the lb/ft scale.  Always better to be safe then sorry....

[limby2000]

Funny enough the bolts I've just bought to replace the overtorqued bolts are arp. Will be double carefull with these ones.