Doing a head bolt swap job soon.
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C63 AMG
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?
Anyone consider getting the heads ported / decked while you're swapping the bolts?
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C63 Weistec Supercharged
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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.
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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.
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From: Kitchener, ON
2010 C63 AMG
It will also unclamp the HG which defeats the purpose of doing them one at a time.
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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?
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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
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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.
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.
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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.
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.
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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.
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.
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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.
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.
Not sure if you all have the torque specs., but if not, here they are.
Regards,
Joe
Last edited by Valvestud; Apr 17, 2015 at 11:34 AM.
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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.
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.
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.
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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.
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.
