Big-end torquing

[Slavvy 0]

Simple question here. I recently put together an m30b34 and I put everything together according to factory specs. I took great pains to do everything perfectly and overall, I'm quite pleased with the result (fingers crossed it doesnt blow up ).

I read something about big end bolts coming loose after x amount of miles (not specifically relating to bmw engines), and that certain cars specify having to re-tighten them after 1000km's. I can't imagine doing this with an m30 in a car because of the sheer P.I.T.A. factor, but now I'm nervous about my engine disintegrating after a few thousand km's.

Is it a good idea to whip the sump off, take out the oil pump and re-do them with loctite, or will it be ok the way I did it (cleaned, oiled, BMW torques)?

[pureboiracer 0]

when i built my engine i locked tighted every single bolt. i wouldnt have done it any other way, and i guess it depends on how much of a gambler you are, but if you didnt use locktight i would be pulling that motor back out again.... imo.

[Silver Fox 43]

If it has been done to the correct torques then you should have no problems. I've built a dozen engines in the last couple of years, and have not had a problem with bolts working lose, and have not locktited any internal bolts to date. None of the bolts I've ever removed from the bottom end have ever been done either, you can tell when a bolt has had Locktite applied.

[pureboiracer 0]

^if he says it ok then its ok...

[sp8s 1]

Have built heaps of engines over the years, used NEW bolts every time and NEVER had anything come loose.

Built engines over 500 hp as well and never a problem when using new bolts/studs. Never loctited any thing, PITA to pull apart anyway.

[Slavvy 0]

If it has been done to the correct torques then you should have no problems. I've built a dozen engines in the last couple of years, and have not had a problem with bolts working lose, and have not locktited any internal bolts to date. None of the bolts I've ever removed from the bottom end have ever been done either, you can tell when a bolt has had Locktite applied.

Have built heaps of engines over the years, used NEW bolts every time and NEVER had anything come loose.

Built engines over 500 hp as well and never a problem when using new bolts/studs. Never loctited any thing, PITA to pull apart anyway.

Brilliant, thanks a lot guys. Just wanted to make sure before the motor went in the car.

[*Glenn* 854]

Did you use new conrod bolts when you assembled the motor?

[Slavvy 0]

Did you use new conrod bolts when you assembled the motor?

I didn't, should I have? I dont know how to remove the bolts from the rods anyway, they didn't push out...

[325_driver 422]

I didn't, should I have? I dont know how to remove the bolts from the rods anyway, they didn't push out...

Always recommended to ensure the conrod bolts are replaced, they stretch, so could loose their effectiveness to torque second time. I had to put my conrod in the vice, and wack them out with a mallet, carefully ofcourse.

[tibbs.james 1]

Not to thread jack but would loctite cause a false torque reading ?

With the some assembly lubes for fastners it can mention to only use 0.8xtorque spec due to the extra lubrication over a "dry fastner"

with loctite being used without doing the calcs this could casue a false reading ?

back on topic ( sorry guys )

I know myself i have had specific bolts just not want to torque up properly where say the other 11 clicked up real nice on the torque wrench.

upon removal and measureing i have found one to be stretched ( used bolts )

I believe reusing bolts is not a huge deal if they have been properally measured and one is not found to have been out of spec vs the others.

in saying this I have reused plenty of main bearing cap bolts but always used BRAND SPANKING rod bolts and head bolts.

there is a speical type of caliper used for measuing stretch on bolts.

[Slavvy 0]

Not to thread jack but would loctite cause a false torque reading ?

With the some assembly lubes for fastners it can mention to only use 0.8xtorque spec due to the extra lubrication over a "dry fastner"

with loctite being used without doing the calcs this could casue a false reading ?

back on topic ( sorry guys )

I know myself i have had specific bolts just not want to torque up properly where say the other 11 clicked up real nice on the torque wrench.

upon removal and measureing i have found one to be stretched ( used bolts )

I believe reusing bolts is not a huge deal if they have been properally measured and one is not found to have been out of spec vs the others.

in saying this I have reused plenty of main bearing cap bolts but always used BRAND SPANKING rod bolts and head bolts.

there is a speical type of caliper used for measuing stretch on bolts.

Hrm...might have to pull the sump off and swap them out then. All of them torqued up perfectly without issue, and the engine is reasonably low km's. I'll have to look into this further.

[*Glenn* 854]

True story.... about 15 years ago

My client who owned Pasta Italia in Parnell owned an E34 535i M30 motor. For no reason at all this car threw a conrod on No5 cylinder. We took the motor out, removed the sump, and sure enough... broken conrod bolt. Des Parsons who worked for me at the time fitted an factory replacement engine and all was fine for about 9 months. In the meantime Des left my employment to work for Team McMillan BMW (and still does). Car got towed in one day and what do you know.... No5 conrod hanging out the side. Car went to TMMBMW (under warranty) It had another motor fitted free of charge and BMW could not give us any answers for the second No5 cylinder conrod bolt breaking. Des painted a target on the block of the new engine on No5 cylinder. The car is somewhere in Australia now.... I wonder if someone has this car or this engine still ?

[pureboiracer 0]

lol.... had a ford focus rental car that had done about 20000k and had thrown a rod and put 2 holes in the block... hadnt even had its 1st service yet...... (but apparently the hole that was in the sump had happened the day before when he had hit a rock...)