HKS vs OEM Headgaskets

Many VQ35DE builders have had issues sealing the original VQ35DE headgaskets beyond 500rwhp using OEM headgaskets and standard ARP head studs torqued to 70-80ft-lb. The CJM 350z experienced these issues starting at 14psi of boost and 575rwhp on the original build. Once the headgaskets were damaged, they started leaking at even 520rwhp @ 11psi of boost. Engine teardown is the only fix, as the the headgaskets cannot just be simply changed out on the VQ35DE. The labor is intensive enough to justify an entire rebuild.

CJM utilized the HKS headgaskets along with a 1/2" headstud modification for the second build. The torque on the headstuds was set to 95lb-ft. So far the combination has been a great success, with not even the slightest signs of any headgasket leakage at all. We would recommend that you contact your local HKS dealer for these headgaskets. The MSRP is $360.00, and they are worth every penny. **update 1/1/09, after a few years of use, the HKS headgaskets have still held strong at 14psi - 18psi of boost, a new engine build is taking place, hks headgaskets may be included in this build, or we may try the new HR series OEM gaskets which have been successful for many lately**

First lets go over some information provided by HKS, then I will show our comparison.

Text copied from HKS USA website: "HKS metal head gaskets are engineered to resist severe levels of heat that are generated by high-horsepower and high-boost applications. All HKS head gaskets are constructed with multiple layers of steel and coated with a special fluorine rubber to provide exceptional sealing. HKS head gaskets are designed to accommodate standard and certain oversized cylinder bores." (Source: http://www.hksusa.com/products/more.asp?id=732)

Text copied from HKS USA website: "The HKS Stopper-Type gasket consists of the maximum layers of plates possible and utilizes a molded stopper ring around each combustion chamber opening."
(Source: http://www.hksusa.com/products/more.asp?id=732)

Images from HKS USA website (click to enlarge):

HKS Advertised Specs: Part #: 23011-AN002 Style: Stopper Bore: 97mm C/R: 10.3:1 Thickness: 0.7mm MSRP $360.00

The CJM Side-By-Side Comparison of the HKS VS OEM Headgaskets:
(CLICK ANY IMAGE IN COMPARISON TO ENLARGE)

NOTE: OEM Gasket is Silver/Black, HKS is all black.

Basic Side By Side Comparison. The HKS rubber coating is a little more "luxurious" and tacky feeling. I would feel confident in the HKS unit providing proper sealing without any copper spray. The OEM units I would probably end up giving a light coating of copper to. The HKS gasket is coated all over, while the OEM gasket is only coated in areas requiring sealing. The cooling and oil jackets appear indentical.

Thickness Comparison:

While HKS advertises a 10.3 C/R, we measured the OEM gasket to a 0.6mm
and the HKS to a 0.7mm. This will just barely reduce compression.

Embossing Comparison:

	The OEM unit has double embossing around each combustion chamber on all 3 layers. The embossing around the cooling and oil jackets is not as aggressive.
	The HKS gasket has half as much embossing around each chamber, but more aggressive embossing around the cooling and oil jackets.

Middle Layer Comparison:

	The Nissan OEM middle layer has embossing that matches the 2 outter layers.
	The HKS unit's middle layer employs the HKS "Stopper" ring, which is a folding over of the layer. This will give extra sealing pressure precisely where needed.

Headstud Bore Comparison:

	OEM headgaskets will just barely fit with 1/2" headstuds without modifications.
	The HKS gaskets are a little more forgiving on the tolerance of a 1/2" stud conversion.

Cylinder Bore Comparison:

	As the image speaks for itself, the OEM gasket isnt entirely suitable for over-sized pistons.
	HKS is forgiving for your typical .020" and .040" over-sized pistons.