Kriston

Ive read that its possible to do them 1 at a time, if thats the case the install should be fairly straight forward. I am also considering it as preventative maintenance.

Anyone consider getting the heads ported / decked while you're swapping the bolts?

average joe

Did mine one at a time, and no issues.

Merc63

We are doing this job this weekend. Guy is just switching to MBs revised bolts, no studs, but the process is still the same.

Jasonoff

Can you do one at a time for a TTY bolt?

I thought all bolts need to be torqued to the elastic deformation point (a specific lower torque) before starting the plastic deformation second pass (an angle/#turn setting)?

I was curious of this. How would you install the updated OE bolts one at a time. Interested to hear the outcome.

Merc63

The same as a stud, remove one, put in the new bolt and torque it to spec.

bhamg

Great!

Jasonoff

Would it not end up having different final torque?

10 bolts torqued to X ft-lb would have the head clamped down at a specific pressure. Then the second stage to get to the required stretch spec.

If the head is already clamped at a higher pressure, you're starting the second stage at a different position.

Merc63

We will probably torque the bolts to the required foot lbs then go in a second wave and do the rotational spec.

Jasonoff

That still wont achieve the same final torque as a freshly installed head following the OE procedure.

It will also unclamp the HG which defeats the purpose of doing them one at a time.

Merc63

So you think 40ftlbs per bolt (or whatever the spec is), that the HG will unclamp with 10 x bolts torqued to x ftlbs?

Jasonoff

I "think" it will be fine. Will the HG with less pressure on it cause any issues? Dunno...

I'm sure you could do the math to find out what the new TTY spec would be starting on a fully clamped head. Any mech engineers want to do the calculations?

mr747

Considering merc63 has completed this exercise on his stage 3 supercharged car I'm sure his theory works and I've had numerous conversations with Steve at weistec and he also confirms you can change the head bolts in the same way

Merc63

No he is right. The head being clamped down already will change the initial torquing when putting in the new bolt. By how much? I have no clue. I don't think it will be by much.

There is still resistance from the threading and the top of the bolt. Really how much will the head be clamped down more than if it was a new gasket, probably a very very small amount.

If we knew what these bolts were supposed to be torqued to in ftlbs it wouldn't be an issue. But the angle/rotation at the end could be slightly off. I don't think it will be off by anything meaningful myself, but I do see his point.

The only other option is installing the new bolts to the first torque setting then coming in a 2nd wave and doing the angle torquing. This will release the gasket of some pressure but it will still be clamped down by 10 bolts at 40ftlbs or so which is still a crap load of pressure on a engine that has zero load.

When I did my studs, we torqued them down to around 70-80lbs I think, then went in a 2nd wave and did the final torquing.

Any mechanical engineers on here? I am certainly not one.

Jasonoff

I would do both stages for each bolt so you don't disturb the HG.

The bolts will be a little tighter if you use the OE TTY spec. Maybe decrease the 2nd stage deg slightly? How much is the question.

BLKROKT

For what it's worth, I agree with both of you guys. You probably can get away with doing one at a time as Merc63 and Weistec have clearly shown us, as well as others on many different engines.

However you should keep in mind that whenever you take the tension off of even one head bolt, the gasket material in that spot will decompress. Any oil you use on the threads may then seep into the gasket where you decompressed it. On a stock C63 with stock compression, this is probably ok. But when you're dealing with the significantly higher cylinder pressures from supercharging, this may compromise the head gasket material and give you a higher chance of blowing it out. If anything, I'd go oil/lubricant free on the new bolts.

Also, you usually want to chase out the threads so that you can get perfect torque readings. Again, probably a bit OCD.

So can you do it? Sure. Should you do it? Probably not - you already have it torn down, why not just do it right. Glad it's working out for some of you though, fingers crossed.

Jasonoff

And is it really that much more difficult to remove the heads and replace the HG? Coolant flush required I'd assume.

Valvestud

Not sure if you all have the torque specs., but if not, here they are.

Regards,

Joe

Jasonoff

Oh yeah, I forgot it was 5 stages. That's very specific, I'm assuming for properly even HG compression and bolt stretch. Did they change the spec at all with the new bolts?

Valvestud

Data from ALLDATAdiy as of this morning. So assume it's current.

Merc63

With one bolt removed and 9 others torqued down, there is still an enormous amount of clamping force on that head and with no load, there is no way in hell any oil is going to seep in between the seal. The lube on the bolt threads goes down into the block which passes through the water jacket. It's impossible for that lube to make its way up to the head to block seal.

if you calculate the clamping force of those 9 bolts, it's huge, especially when there is no load on the engine if it's not running. Fluids take the path of least resistance. I know some old school guys have a hard time with this method but it's nothing new. Diesel guys have been doing this for years when they replace factory bolts with arp studs.

I remember reading an article where Bmw does this exact process with one of their engines, they had head bolt problems too.

I've debated this before with guys when I did it to my own engine and tons of guys said oh that won't work, yada yada, and yes it did work, I have be running 10lbs of boost hard for 26,000km with zero issues.

Jasonoff

Haters gonna hate...

The real question is. How do you torque an OE bolt with this method?

Merc63

Did one bank today. We just did the whole torque sequence in on shot on each bolt instead of letting any pressure off the gasket.

So we would torque to 50nm then do 3 turns of 90degrees. My torque wrench has a gauge so we could see how much torque was applied. In the 90 degree turns, the last two were pretty much the same amount of torque, hitting around 110-115nm. That's the stretching portion of the sequence. The bolts that came out were stretched about 1mm or so longer than the new ones.

Doing the other bank tomorrow.

This car has 125,000km on it. Valve train looked in good shape and the bolts that came out didn't have as much rust on them as mine when I removed them.

mr747

Merc63 what year is your mates car??

mthis

Good Chit Merc. keep up the good work.

Merc63

Appears to be a 2009