Shaved head - thicker Headgasket?
11-08-2012, 04:24 PM
#1
Pro
Thread Starter
Shaved head - thicker Headgasket?
The head is away to be resurfaced, they estimate that 0.15 - 0.20mm is neede to get the surface straight.
We have a Widefire headgasket, but I wonder if it would be better to go for the original thicker gasket? I seem to remember it was 0.3mm thicker.
We have sent the turbo to ETG Technic in Germany to be rebuilt and upgraded, setup is a hybrid turbo with chip and 3.8bar FPR, according too ETG this should produce around 330chp.
So, what is the best be? Reducing or increasing compression, 1.1mm or 1.4mm headgasket?
We have a Widefire headgasket, but I wonder if it would be better to go for the original thicker gasket? I seem to remember it was 0.3mm thicker.
We have sent the turbo to ETG Technic in Germany to be rebuilt and upgraded, setup is a hybrid turbo with chip and 3.8bar FPR, according too ETG this should produce around 330chp.
So, what is the best be? Reducing or increasing compression, 1.1mm or 1.4mm headgasket?
11-09-2012, 01:10 PM
#5
Pro
Thread Starter
I did a search, and found that Porsche recommends using the thicker gasket if you remove more that 0.1mm
I will check the actual measuerement on the head but I have ordered a thicker gasket.
I will check the actual measuerement on the head but I have ordered a thicker gasket.
11-09-2012, 02:39 PM
#6
Rennlist Junkie Forever
The thing to remember is that unless you bought the car new, you don't know how much (if any) has been milled off head by previous owners. To know this you can measure the pad on the head.
No matter... as you mill the head, you retard the cam timing. You can get an adjustable cam sprocket or an offset cam key (which comes in 2 or 4 degree keys) to correct for this or just to change the cam timing if desired.
Something to think about.
TonyG
No matter... as you mill the head, you retard the cam timing. You can get an adjustable cam sprocket or an offset cam key (which comes in 2 or 4 degree keys) to correct for this or just to change the cam timing if desired.
Something to think about.
TonyG
11-09-2012, 02:40 PM
#7
Rennlist Junkie Forever
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11-09-2012, 02:44 PM
#8
Rainman
Rennlist Member
Rennlist Member
The thing to remember is that unless you bought the car new, you don't know how much (if any) has been milled off head by previous owners. To know this you can measure the pad on the head.
No matter... as you mill the head, you retard the cam timing. You can get an adjustable cam sprocket or an offset cam key (which comes in 2 or 4 degree keys) to correct for this or just to change the cam timing if desired.
Something to think about.
TonyG
No matter... as you mill the head, you retard the cam timing. You can get an adjustable cam sprocket or an offset cam key (which comes in 2 or 4 degree keys) to correct for this or just to change the cam timing if desired.
Something to think about.
TonyG
11-09-2012, 03:14 PM
#9
Rennlist Member
Interesting stuff . I did not think about this when i replaced the head with a fresh rebuilt and shaved one. When i rebuild the old one and open it up again i will try to measure.
What are these marks (pad) people refer too ?
11-09-2012, 03:20 PM
#10
Pro
Thread Starter
Yes, I was considering the timing also. I know about those cam keys, I believe they are Mercedes items and can be bought from any Merc dealer!
It is certainly possible to calculate the amount of cam retard, but you need to know the data to do it correct. And as far as I can see it it would be a linear correlation, so if someone did the calculation it would be easy to create a formula for it.
But how about this: When you shave the head you increase the static compression, but at the same time you retard the cam and that decreases the dynamic compression (intake valve closes later). Who knows, maybe we all should do it, same dynamic compression means same performance on lower rpms, but retarded cam means better filling on high rpms. If you can avoid detonation that is...
It is certainly possible to calculate the amount of cam retard, but you need to know the data to do it correct. And as far as I can see it it would be a linear correlation, so if someone did the calculation it would be easy to create a formula for it.
But how about this: When you shave the head you increase the static compression, but at the same time you retard the cam and that decreases the dynamic compression (intake valve closes later). Who knows, maybe we all should do it, same dynamic compression means same performance on lower rpms, but retarded cam means better filling on high rpms. If you can avoid detonation that is...
11-09-2012, 07:56 PM
#11
Rennlist Junkie Forever
But how about this: When you shave the head you increase the static compression, but at the same time you retard the cam and that decreases the dynamic compression (intake valve closes later). Who knows, maybe we all should do it, same dynamic compression means same performance on lower rpms, but retarded cam means better filling on high rpms. If you can avoid detonation that is...
TonyG
11-10-2012, 08:42 PM
#12
Rennlist Member
I believe I saw a pic on here once upon a time of a small line on the head marking how far down it could be shaved. Can someone tell me and/or post a pic of where the limit mark is on the head?
11-11-2012, 06:25 PM
#13
Pro
Thread Starter
I did a search on this forum and found a page from the workshop manual. There is not a limit mark, but there is a machined ridge, and you measure the thickness of this ridge. The standard distance is 24 +/-0.1mm and the wear limit is 23.6mm. I am not sure, but it may be possible to measure this distance without dismantling the head.
Last edited by Ian928; 11-12-2012 at 04:49 AM.
11-11-2012, 08:47 PM
#14
Last edited by Adker; 05-16-2013 at 10:10 PM.