Vanos now or later?

[mrgizmo04]

Yeah, and in comparison to the rest of the cost, $24 is nothing. Other issues with stock bolts is that they're extremely easy to overtorque if you don't have a well calibrated torque wrench. Safer to just use stronger bolts (and they should be less likely to back out if you can torque them more anyway).

I don't think we need to keep going back and forth, but I'll just add this.

Hopefully whoever takes on the job (especially a shop) has proper tools and torque wrenches and understand the actual mode of failure to fix however they decide to fix at the end. Also, there is a reason why Beisan doesn't sell the bolt kit (it is not omitted by mistake).

[terra]

I don't think we need to keep going back and forth, but I'll just add this.

Hopefully whoever takes on the job (especially a shop) has proper tools and torque wrenches and understand the actual mode of failure to fix however they decide to fix at the end. Also, there is a reason why Beisan doesn't sell the bolt kit (it is not omitted by mistake).

Honestly, I think you're giving dangerous advice in this regard. It'd be one thing if we were talking about a major expense, but it's pennies. Guarantee you most shops are going to just "good and tight" bolts that call for 6 lb-ft. It was very well documented on the old forum that numerous shops and individuals overstretched the stock bolts. Coupled with loctite and some residual oil, it's extremely easy to torque them beyond what they can handle. I think it is very short sighted to not replace them, let alone not go for a higher class bolt.

Beisan does recommend replacing the bolts rather than reusing the originals. And I would go a step beyond and get stronger bolts.

[mrgizmo04]

Honestly, I think you're giving dangerous advice in this regard. It'd be one thing if we were talking about a major expense, but it's pennies. Guarantee you most shops are going to just "good and tight" bolts that call for 6 lb-ft. It was very well documented on the old forum that numerous shops and individuals overstretched the stock bolts. Coupled with loctite and some residual oil, it's extremely easy to torque them beyond what they can handle. I think it is very short sighted to not replace them, let alone not go for a higher class bolt.

Beisan does recommend replacing the bolts rather than reusing the originals. And I would go a step beyond and get stronger bolts.

My intention is not to be dangerous, but to provide some background, information and insight. Sometimes attempt at the "why".

I agree they are cheap, and there is no harm in replacing the bolts.

To me the topic we are discussing is somewhat parallel to understanding and knowledge that existed years ago about subframe failures and that plates were the solution. Until Vince and later Cayn from CMP did further analysis to better understand actual underlying modes of failure and how to best reduce/prevent the issue. Some people still think plates are enough because they have not followed latest info and r&d.

For the bolts in discussion, I can definitely see the panic ages ago as the bolts were shearing and the proposed solution would be to make stronger ones. Sure. Until better understanding about the actual mode of failure became apparent (loosening up and backing out which resulted in shearing).

Beisan procedure was written about 7-8 years ago I don't know what revisions have been made to that particular section on bolts. I actually discussed the bolts with Raj as recently as 2 weeks ago, because I told him that as I find folks that I need to help with VANOS, we inadvertently need to order the cam bolts just in case, and since he does not carry them we have to source them from dealers or Lang. He reiterated the underlying issue of the bolts backing out and there was no issue with reusing them with locktite.

On my car when I did vanos 3 years ago, mine were tight so I reused with locktite. Im almost 30k hard miles later, at this point which include everything from daily with baby, autox, canyons and track.

Like I said, I'm here to help and to provide info, which I think is valuable for folks to know. What you do with that info is a choice. If everyone sleeps better at night replacing the bolts, awesome.

[Albertan]

When I was doing vanos, I did 4 cars. I used grade 10.9 bolts. I set up a bit of a test rig. A 6mm 10.9 bolted into a 10.9 grade nut could torque to 20 ft lbs before failure. So if grade 8.8 is supposed to be 6 ft lb and you change to 10.9, no one should be able to twist them off if they are aiming for 6 ft lbs (72 in lbs). Personally, I think I did 8 or 10 ft lbs plus loktite Blue. These will give a measure of safety.

[terra]

There was never much of a misunderstanding on the failure mode. Even when I bought the car a decade ago it was common knowledge that the issue was that they’d back out and ultimately let the cam gears spin without the cam itself spinning.

Being able to torque to a higher spec will make it less likely for the bolt to back out on its own. Using loctite should make it less likely as well. Doing both together will give the most security. And even if you shoot for the stock torque spec, a 10.9 or 12.9 bolt will give you the margin of error necessary to tighten without risking over tightening.

We’re all here to provide information. I will call out information that I think is likely to result in engine failure.

[mrgizmo04]

There was never much of a misunderstanding on the failure mode. Even when I bought the car a decade ago it was common knowledge that the issue was that they’d back out and ultimately let the cam gears spin without the cam itself spinning.

Being able to torque to a higher spec will make it less likely for the bolt to back out on its own. Using loctite should make it less likely as well. Doing both together will give the most security. And even if you shoot for the stock torque spec, a 10.9 or 12.9 bolt will give you the margin of error necessary to tighten without risking over tightening.

We’re all here to provide information. I will call out information that I think is likely to result in engine failure.

This is now somehow on a whole other level. Information that I provide (which is researched and confirmed/backed up by people who specialize in either working on these cars and VANOS (shops and mechanics) or those who are constantly making parts for the VANOS problem areas (ala Raj/Beisan)) is deemed dangerous. And fixing the underlying problem and the mode of failure is now likely to cause engine failure? With all due respect, Terra...

[Dafoe]

Hey fellas!!! I’ve done well over a hundred Vanos jobs and have always done the cam bolts... I wouldn’t want to do all the work getting everything apart and not replace them with loctite. I will say that I’ve personally seen only two cars with loose bolts.

I’ve logged 150k miles on my last set... put new ones in during the rebuild.

Glad to see some familiar names in this forum.