Rod bolt won't torque to spec

[Davisca455]

I'm trying to figure out what would explain only the first part of the threads shearing off?

My only theory is that when the OEM bolt was stretched a second time the thread pitch changed, nearest the shank?
Would that act like a jack and explain why only part of the threads completely failed?

[Green-Eggs]

Originally Posted by DukeofAlexandria

You measure multiple spots over the journal and compare your numbers. Ideally you measure in multiple spots with the main OUT of the car so you can go around the entire thing. You'd need a micrometer and bore gauge. If these guys are even semi-professional, then they should have both of those tools and high quality ones at that.

Sure, you can get away with using plasti-gauge, I've built plenty of american motors with the stuff, but with the tolerances in these bearings/engines, I probably wouldn't go that route. If these guys are using plasti-gauge and going that route, that's a non-starter for me.

-Duke

You can't get a bore gauge inside the S65 to measure the rod big-end. Plastigage is your only choice to "approximate" clearance with the engine inside the car.

Originally Posted by Davisca455

...and my understanding is that BE pre measures all of their shells and builds their kits according to a target clearance that their research has determined.
So, if your crank is within the tolerances of what BE expects it to be, then the bearings should create the intended gap that BE was aiming for.
I don't know if it's a fact, but I've heard that some shops don't measure the crank rod journals, but give the journals a visual inspection and then proceed.

It is a fact, plenty of photos posted to show it. Bert will be at my house this weekend measuring bearings.

[GearKid]

Originally Posted by SAMM3Y

Any pics of the bolts that came out? I would imagine it would have been dragging thread with it.

I don't have pics but all the bolts look perfect. Of course if there was thread debris when this first happened it's easy enough to clean the bolt up before presenting them to the customer.

[ha9981]

Anyone else think it's kind of odd BE requires plastigage proof for warranty purposes yet they state/admit how it is anything but accurate for measuring purposes. So why waste the money on labour.

I'd understand asking for pics of crank and prior bearings to be sure nothing was badly off clearances wise.

[Davisca455]

Originally Posted by GearKid

I don't have pics but all the bolts look perfect. Of course if there was thread debris when this first happened it's easy enough to clean the bolt up before presenting them to the customer.

Are you referring to the OEM bolts?

[GearKid]

Originally Posted by Davisca455

Are you referring to the OEM bolts?

Yes. The ARP bolts for rod #8 had not even been threaded into the rod when I saw them. They had anti seize grease still on them.

[akkando]

Did they give a reason why they measured with previously used single use only oem bolts instead of the new ARP BE bolts? I would assume in the case of a failure and a warranty claim was made, BE would want evidence that a proper bolt was used during measurement?

[Scharbag]

Originally Posted by akkando

Did they give a reason why they measured with previously used single use only oem bolts instead of the new ARP BE bolts? I would assume in the case of a failure and a warranty claim was made, BE would want evidence that a proper bolt was used during measurement?

TIS specifies to use the old OE bolts to check clearance. That is not the issue.

[ha9981]

Originally Posted by Scharbag

TIS specifies to use the old OE bolts to check clearance. That is not the issue.

Exactly what I remembered too. Got me double thinking when I saw SYT_Shadow comment earlier that they shouldn't be used. Which is incorrect.

Nothing wrong with using those old bolts for the plastigage step.

What if someone used a high torque gun on clockwise trying to undo the rod cap. Wonder if that's what it takes to ruin the rod threading.

[SYT_Shadow]

Originally Posted by ha9981

Exactly what I remembered too. Got me double thinking when I saw SYT_Shadow comment earlier that they shouldn't be used. Which is incorrect.

Nothing wrong with using those old bolts for the plastigage step.

What if someone used a high torque gun on clockwise trying to undo the rod cap. Wonder if that's what it takes to ruin the rod threading.

Correct. I misread and thought they were reassembling the engine with OEM bolts, which sounded all kinds of crazy!

To use old oem bolts to check clearance is fine

[GearKid]

Originally Posted by Scharbag

TIS specifies to use the old OE bolts to check clearance. That is not the issue.

The shop confirmed this practice. As I understand, BE wants to ensure your original bearing clearances are within the tolerances the BE's are designed to accommodate. The old bearings and bolts are needed to get this measurement.

[Scharbag]

Originally Posted by GearKid

The shop confirmed this practice. As I understand, BE wants to ensure your original bearing clearances are within the tolerances the BE's are designed to accommodate. The old bearings and bolts are needed to get this measurement.

If you are using ARP bolts, use those to check clearance as they can be re-used. No need to piss around with the OE bolts and their BS torque sequence.

[Bubbles]

^ agreed pretty wild that this guy pays a shop to do the work and gets left with a coffee table motor.

[exVtekGuy]

Originally Posted by GearKid

[
The shop was not about to admit guilt and I respect that. Theories as to the rod threads being buggered as a pre-existing condition were weak at best. The best theory put forth was excessive heat due to oil starvation from lack of regular oil changes. .

How does lack of oil change cause oil starvation or excessive heat? :

[DrFerry]

Just cross linking this for the OP:
https://www.m3post.com/forums/showpo...postcount=2089

Build thread for 4.4L stroker results in 61HP gain. https://www.m3post.com/forums/showthread.php?t=1423749

Out of the fire: 4.4L S65 stroker install https://www.m3post.com/forums/showthread.php?t=1414377

VAC Motorsports | VAC 4.4 S65 Stroker Kit Build (CP, Carrillo, Darton, Schrick) https://www.m3post.com/forums/showthread.php?t=739118
.

[GearKid]

Originally Posted by DrFerry

Just cross linking this for the OP:
https://www.m3post.com/forums/showpo...postcount=2089

Build thread for 4.4L stroker results in 61HP gain. https://www.m3post.com/forums/showthread.php?t=1423749

Out of the fire: 4.4L S65 stroker install https://www.m3post.com/forums/showthread.php?t=1414377

VAC Motorsports | VAC 4.4 S65 Stroker Kit Build (CP, Carrillo, Darton, Schrick) https://www.m3post.com/forums/showthread.php?t=739118
.

Thanks for all the links! From the sounds of it, these strokers look like they need hot cams and a very smart tune to get the full potential out of them. Reading between the lines these motors seem like they are best for the end user that will be tracking the car.
For me, first priority is long term reliability. What's the opinion of the forum regarding a new stock motor vs the Dinan 4.2L? I'm leaning towards the 4.2L since it addresses several issues associated with the stock build. Would the M3 community perceive the Dinan motor as an upgrade?

[M3 hacker]

Originally Posted by ha9981

Exactly what I remembered too. Got me double thinking when I saw SYT_Shadow comment earlier that they shouldn't be used. Which is incorrect.

Nothing wrong with using those old bolts for the plastigage step.

What if someone used a high torque gun on clockwise trying to undo the rod cap. Wonder if that's what it takes to ruin the rod threading.

Having changed my cars rod bearings myself - I couldn’t think of a reason on how this could happen until I read this post.

Mechanics use impact wrenches too much this days.

Hope it all works out for you!

[akkando]

Originally Posted by GearKid

Thanks for all the links! From the sounds of it, these strokers look like they need hot cams and a very smart tune to get the full potential out of them. Reading between the lines these motors seem like they are best for the end user that will be tracking the car.
For me, first priority is long term reliability. What's the opinion of the forum regarding a new stock motor vs the Dinan 4.2L? I'm leaning towards the 4.2L since it addresses several issues associated with the stock build. Would the M3 community perceive the Dinan motor as an upgrade?

Can you run the stock tune on the Dinan motor, at least long enough to get the monitors ready for smog? Smogging a car in California is soon to require a stock tune.

[Ximian]

Originally Posted by Green-Eggs

... Bert will be at my house this weekend measuring bearings.

You party animals

[GearKid]

Originally Posted by akkando

Can you run the stock tune on the Dinan motor, at least long enough to get the monitors ready for smog? Smogging a car in California is soon to require a stock tune.

Great point. I'll confirm.

[GearKid]

Originally Posted by M3 hacker

Having changed my cars rod bearings myself - I couldn't think of a reason on how this could happen until I read this post.

Mechanics use impact wrenches too much this days.

Hope it all works out for you!

The tech (and the shop) are very knowledgeable and just talking with them while we were all under the car, I'm pretty confident he was following the BMW procedure for their bolts. This was the 8th rod to be clearanced, so his process worked fine for the first 14 bolts.

[Bubbles]

Originally Posted by GearKid

The tech (and the shop) are very knowledgeable and just talking with them while we were all under the car, I'm pretty confident he was following the BMW procedure for their bolts. This was the 8th rod to be clearanced, so his process worked fine for the first 14 bolts.

Not throw cold water in this but I stripped the last oil pickup bolt during a bearing swap. I chalked it up to wanting to get the project complete and being too comfortable. A bit of duct tape and luck got me out a potential disaster. It happens to all of us and the tech may have forgot to flip the switch on the impact gun and wanted out of the oil drip shower.