engine overhaul / big ends tourge settings

[shadetree]

hey guys I am in the process of redoing my engine I have a small problem with the big ends the manual I have says I must tighten in two stages 1st:20nm 2nd:70 deg, problem is that my tourqe wrench only starts at 28nm. Any sugestions on what I should do, other than getting another tourqe wrench.

[spoon320]

Unless you can find a torque demultiplier (if such a thing exists)......

Get a smaller torque wrench

Or maybe you could calculate the length of bar needed to get that torque on that thread pitch..... maths

Welcome to the zone btw

[Templ8e30]

The only thing you can do is buy or borrow another torque wrench. The big end cap bolts torque is critical, they take a lot of punishment and must be tightened correctly

Sorry matey,

Iain T

[Turbo-Brown]

Just a thought, but thread pitch doesn't play a part in torque calculating, just how much load is applied by a torque

[spoon320]

Just a thought, but thread pitch doesn't play a part in torque calculating, just how much load is applied by a torque

Tsk! - I stand corrected, been a long time since i did any engineering maths

[m-dtech]

just torque the first stage to 28nm for all the difference it will make.

[Templ8e30]

just torque the first stage to 28nm for all the difference it will make.

Whooooaaaaa, dont do that !!!! the big end bolts are stretch bolts and if you over torque them they'll be weakened and probably snap

If you do the maths (and I'm crap at maths) the big end bolts on a 325i have to decelerate a piston/rod assembly weighing about 500grams from 487metres/sec to zero then accelerate from zero to 487m/s 6500 times a minute at full chat. Over stretch the bolts and you're gonna throw a rod and need a new engine !

For the sake of Ԛ£30 get a smaller torque wrench and do the job right first time

Cheers,

Iain T

[m-dtech]

just torque the first stage to 28nm for all the difference it will make.

Whooooaaaaa, dont do that !!!! the big end bolts are stretch bolts and if you over torque them they'll be weakened and probably snap

If you do the maths (and I'm crap at maths) the big end bolts on a 325i have to decelerate a piston/rod assembly weighing about 500grams from 487metres/sec to zero then accelerate from zero to 487m/s 6500 times a minute at full chat. Over stretch the bolts and you're gonna throw a rod and need a new engine !

For the sake of Ԛ£30 get a smaller torque wrench and do the job right first time

Cheers,

Iain T

they are getting torqued to 70nm anyway

[Templ8e30]

Nope they are getting angle torqued to 70 degrees from 20NM, 70 degrees from 28NM will very likely break them.

Cheers,

Iain T

[Turbo-Brown]

I doubt they'd break with an extra 8Nm, but they're designed to be tightened to a specific torque, so tighten them to that torque!

[shadetree]

Hey guys I managed to calculate the torque on the big ends with the help of one of my engineering mates.

Got the engine back in the car the timing is sorted, battery is newly charged but the car wont start! the starter turns the engine over but thats it any insight would be greatly appreciated.

the HT leads are a bit worn so I am going to replace those the end of the month and I think my AFM is on its way out aswell so getting a new one of those aswell.

[Andy335Touring]

Check for the basic stuff like have you got a spark and fuel, double check all the connections(electrical and plumbing) are connected properly

[shadetree]

Hey guys

checked it again yesterday and when I turn the key I get a rapid ticking noise, the starter doesnt turn over and the number 9 fuse blows, I dont have a manual with the fuse numbers on them. so if someone knows what is cutting I would greatly appreciate it