Member Since: 14 Apr 2019
Location: Westbury
Posts: 2459
Head gasket
Hi is there a guide to selecting the correct head gasket thickness?
I am just rebuilding my 3.0 sdv6 engine and both head gaskets are different thicknesses but the pistons protrude from the cylinders by the same amount?
I cant seem to find any referance guides?
24th Nov 2020 6:44 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4626
There's several different thickness grades indicated by the number of tangs on the end of each gasket.
The grades start at 1.17mm, 1.22, 1.27 & 1.32. What was on there when you stripped it?yµ (idµ - eAµ) ψ=mψ
24th Nov 2020 7:13 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2459
One side was 1.22mm and the other was 1.27mm i have all new pistons and they are all around 0.56mm protruding out of the cylinder.
I have now found the following information and will be measuring my pistons again to make sure.
Cylinder Head Gasket
The cylinder head gasket is a three-layer, laminated
steel type and is available in five different thickness.
The choice of gasket thickness is dependent on the
maximum piston protrusion. Gasket thickness is
identified by serrations cut into the front end of the
gasket.
To calculate the correct cylinder head gasket thickness,
each piston must be measured at two points, with an
average of the two measurements taken to determine
the piston protrusion. The highest of the three
measurements will determine the gasket required for
that particular cylinder head.
NOTE: The difference between the maximum and
minimum protrusion measurement in any one bank
should not be greater than 0.1mm. It is permissible to
have a different grade of gaskets between the LH and RH
Click image to enlarge
24th Nov 2020 7:20 pm
PROFSR G
Member Since: 06 Mar 2017
Location: Lost
Posts: 4626
Sorted yµ (idµ - eAµ) ψ=mψ
24th Nov 2020 7:38 pm
robpenrose
Member Since: 12 Jan 2016
Location: Surrey / SW London
Posts: 2136
aja4x4 wrote:
One side was 1.22mm and the other was 1.27mm i have all new pistons and they are all around 0.56mm protruding out of the cylinder.
I have now found the following information and will be measuring my pistons again to make sure.
Cylinder Head Gasket
The cylinder head gasket is a three-layer, laminated
steel type and is available in five different thickness.
The choice of gasket thickness is dependent on the
maximum piston protrusion. Gasket thickness is
identified by serrations cut into the front end of the
gasket.
To calculate the correct cylinder head gasket thickness,
each piston must be measured at two points, with an
average of the two measurements taken to determine
the piston protrusion. The highest of the three
measurements will determine the gasket required for
that particular cylinder head.
NOTE: The difference between the maximum and
minimum protrusion measurement in any one bank
should not be greater than 0.1mm. It is permissible to
have a different grade of gaskets between the LH and RH
Click image to enlarge
If it had different thicknesses on each bank, does that indicate the head gaskets have been changed since being built in the factory?
Current: D4 HSE
Previous: BMW Z4M Coupe
Previous: Land Rover Defender 90 CSW Td5
Previous: Land Rover Discovery Td5 ES
if you think about the cumulative tolerances ... polished crank/con-rod/piston and the differences are still within 0.249 mm min/max then differing gaskets at build are a response to those, albeit minute, differences.
IIRC, a blueprinted engine where the optimum/balanced parts are used and tolerances are minimal increases the costs per engine phenomenally ... although it does boost performance somewhat too.
24th Nov 2020 11:00 pm
aja4x4
Member Since: 14 Apr 2019
Location: Westbury
Posts: 2459
robpenrose wrote:
aja4x4 wrote:
One side was 1.22mm and the other was 1.27mm i have all new pistons and they are all around 0.56mm protruding out of the cylinder.
I have now found the following information and will be measuring my pistons again to make sure.
Cylinder Head Gasket
The cylinder head gasket is a three-layer, laminated
steel type and is available in five different thickness.
The choice of gasket thickness is dependent on the
maximum piston protrusion. Gasket thickness is
identified by serrations cut into the front end of the
gasket.
No they can come from factory with different size gaskets.
To calculate the correct cylinder head gasket thickness,
each piston must be measured at two points, with an
average of the two measurements taken to determine
the piston protrusion. The highest of the three
measurements will determine the gasket required for
that particular cylinder head.
NOTE: The difference between the maximum and
minimum protrusion measurement in any one bank
should not be greater than 0.1mm. It is permissible to
have a different grade of gaskets between the LH and RH
Click image to enlarge
If it had different thicknesses on each bank, does that indicate the head gaskets have been changed since being built in the factory?
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