Connecting Rod Bolts

[bjz!]

Do you have a part number for the older M11 bolts? Are these the same as the S50 euro bolts?

Actually i dont have a part number, but you can use bmwfans.info

[DropTopKingM3]

Did BMW ever make replacement m11 bolts in the past? Or was this not a part you couldn’t buy years back?

[Thoglan]

Did BMW ever make replacement m11 bolts in the past? Or was this not a part you couldn’t buy years back?

As far as I know they were never available. The bmw advice was to reuse due to them as they are not torque to yield and they were matched to the rod. They have to go back into exactly the same thread that they came out of. Can't even mix them side to side on the same rod. Which is why I'm would be uneasy putting an ARP bolt in. I would be reusing them all day over replacing with an aftermarket standard bolt.

[Tbonem3]

On real oem, the bolt is shown in the picture, but its details/part number are missing and it says "see repair manual"

[heinzboehmer]

Yeah I've looked for them before and was unable to find them. I don't think you could ever buy the M11 bolts by themselves.

[TexaZ3]

Because of the metallurgy of ARP bolts, you typically need to torque them more than factory spec to get sufficient bolt stretch (which provides the clamping force). This extra torque can cause the bores to ovalize.
Having said that, I don't know the torque specs for this application, but this does happen with their other engine bolts. To correct this, the bores need to be honed with bolts in place to correct the ovalization.

Right, so its an installation technique, not a problem with the fastener.

[Obioban]

Right, so its an installation technique, not a problem with the fastener.

... sure, but you can only hone the bores with the engine out of the car and the rods out of the engine... and the overwhelming majority of rod bearing installs are done with the engine in the car.

Since the only real benefit of the ARPs is easier install, kind of undermines the point, eh?

[Thoglan]

... sure, but you can only hone the bores with the engine out of the car and the rods out of the engine... and the overwhelming majority of rod bearing installs are done with the engine in the car.

Since the only real benefit of the ARPs is easier install, kind of undermines the point, eh?

Not to mention having to remove the pistons which adds a lot of cost. Even when I did my complete motor rebuild and had the option to install arps I opted not to. There is no measurable evidence that the M11 bolts stretch at all given the torque spec for them is fairly low for the size of the bolt. There's anecdotal evidence of a couple race cars in NZ that get bearings changed every 200 race hours with reused bolts still going on their second or third change.

[digger]

Because of the metallurgy of ARP bolts, you typically need to torque them more than factory spec to get sufficient bolt stretch (which provides the clamping force). This extra torque can cause the bores to ovalize.
Having said that, I don't know the torque specs for this application, but this does happen with their other engine bolts. To correct this, the bores need to be honed with bolts in place to correct the ovalization.

you do not need to torque them more unless you want additonal clamp over the originals. the torque does not cuase ovaliing the clamp does. torque them to the same clamp as OE bolts then its merely a replacment bolt with unused reserve (i.e better mechanical propeties)

[Gregdepot]

You can use the ARP S50 Euro bolts, Lang racing did a bench test and at 68ftlbs they do work. I have them in my car. I got the same response from ARP. DO NOT use the the S50 50ftlbs spec or it will be out of round.

[Seattleswimboy]

You can use the ARP S50 Euro bolts, Lang racing did a bench test and at 68ftlbs they do work. I have them in my car. I got the same response from ARP. DO NOT use the the S50 50ftlbs spec or it will be out of round.

What about the stretch of 0.0065-0.0070 that is speced? I just did my rod bearings and used the arp m10 bolts. I used the stretch method rather then torque. Hope I didn't under stretch them by using the stretch spec that came with them.

[Gregdepot]

What about the stretch of 0.0065-0.0070 that is speced? I just did my rod bearings and used the arp m10 bolts. I used the stretch method rather then torque. Hope I didn't under stretch them by using the stretch spec that came with them.

If you used the specs for the S54 the M11 bolts 70ftbs or the stretch specs you should be good on the M10 or M11 if you used stretch spec for the M10 bolts from ARP for the S50 Euro you will want the re tq them they would not be round or in spec for the S54.

[Seattleswimboy]

If you used the specs for the S54 the M11 bolts 70ftbs or the stretch specs you should be good on the M10 or M11 if you used stretch spec for the M10 bolts from ARP for the S50 Euro you will want the re tq them they would not be round or in spec for the S54.

I just got off the phone with ARP tech support. They said the 50'lbs is the correct torque for that bolt regardless if its used on the s50 or s54. If you torque beyond the 50 lbs you will exceed the stretch limit if the bolt and bolt failure may occur. He also said that their bolts are not oem replacement bolts and regardless of application the rods must be resized to obtain a round bore with their bolts. For oem replacement always use OEM bolts to obtain a round bore.
I told him some shops are torquing higher with their bolts to achieve the round bore and he said that is not the correct way to use their bolts and while you might be able to get away with it your risking bolt failure....

So I guess unless you are pulling the rods to have them resized ARP bolts should never be used in any engine....

So what do you guys think I should do now? I just got my car all put back together and running again. After replacing the rod bearings and using the arp m10 bolts stretched to 0.065-0.070 per ARP instructions. Should I tear it all back apart and replace with oem bolts?

[Gregdepot]

I just got off the phone with ARP tech support. They said the 50'lbs is the correct torque for that bolt regardless if its used on the s50 or s54. If you torque beyond the 50 lbs you will exceed the stretch limit if the bolt and bolt failure may occur. He also said that their bolts are not oem replacement bolts and regardless of application the rods must be resized to obtain a round bore with their bolts. For oem replacement always use OEM bolts to obtain a round bore.
I told him some shops are torquing higher with their bolts to achieve the round bore and he said that is not the correct way to use their bolts and while you might be able to get away with it your risking bolt failure....

So I guess unless you are pulling the rods to have them resized ARP bolts should never be used in any engine....

So what do you guys think I should do now? I just got my car all put back together and running again. After replacing the rod bearings and using the arp m10 bolts stretched to 0.065-0.070 per ARP instructions. Should I tear it all back apart and replace with oem bolts?

Id contact Lang racing, he maybe able to give you a real world answer, maybe stretching them gives the extra tq. When I talked to ARP they said they were never tested by them in a S54. If anyone knows its likely Lang racing they seem to have done the most testing on this. There was many post about this by them on the old forum that vanished.

[Gregdepot]

I just got off the phone with ARP tech support. They said the 50'lbs is the correct torque for that bolt regardless if its used on the s50 or s54. If you torque beyond the 50 lbs you will exceed the stretch limit if the bolt and bolt failure may occur. He also said that their bolts are not oem replacement bolts and regardless of application the rods must be resized to obtain a round bore with their bolts. For oem replacement always use OEM bolts to obtain a round bore.
I told him some shops are torquing higher with their bolts to achieve the round bore and he said that is not the correct way to use their bolts and while you might be able to get away with it your risking bolt failure....

So I guess unless you are pulling the rods to have them resized ARP bolts should never be used in any engine....

So what do you guys think I should do now? I just got my car all put back together and running again. After replacing the rod bearings and using the arp m10 bolts stretched to 0.065-0.070 per ARP instructions. Should I tear it all back apart and replace with oem bolts?

Also we did measure all of bolts all but one were the same
size then measured one the in spec and the out of spec ones after tqing to 68ft and the bolts didnt change length when removed so I don’t think the limits of the bolt were exceeded.

but yeah I think Lang would be the closest to an expert on this.