All Head Gaskets are Not Created Equal

We’ve been doing a lot of product testing at Cosworth recently which is a good thing. Real company = real products = real research & development = real engineering. No Ebay made in China shit here man. However, just because something is made in the USA by a reputable company, it doesn’t mean that it is a quality product. You find out all kinds of things in testing.

Cosworth has been coming out with some kick ass head gaskets lately. They provide the engine builder with Japanese multi layer stainless steel quality, but priced 1/2 way in between the JDM and USDM gaskets. As we develop more applications, we have more testing to do since we must validate our designs and sometimes also check a competitor’s product. To do this, we take some expensive ass pressure film and sandwich it in between the block and head gasket. Obviously, all sealing surfaces must be perfectly flat and free of imperfections. Then we torque the head on top of everything with the head bolt/stud of choice. The pressure film creates a color coded imprint that shows how well the clamping force is distributed. Obviously you want a high clamping force around the cylinders. Of course you can’t forget the water/oil jackets either. The higher the pressure, the brighter the imprint. We’ve found some very surprising results. A leading US multi-layer stainless steel gasket manufacturer actually manufactures some pretty weak gasket designs. In some instances they are worse than stock.

Here are some results from a popular Japanese 2.0L in-line 4 cylinder iron block/aluminum head factory turbocharged engine. No names, models, or manufacturers in this blog post. You figure out which engine. If you can’t, you’re probably either a dumb shit or a non-enthusiast in which case I’m not sure why you’re reading this. Ok, here’s a hint: it’s four wheel drive. No not the one with the flat engine.


This test was performed with 8740 ARP 11mm studs with torque at 90 ft./lbs.

LEFT: This US made multi-layer stainless gasket has a thin sealing line around the cylinder and distortion right around the head bolts which compromises the strength seal. You’ll also see the color is dull which means the clamping force is low. The funny part is that the primary seal (immediately around the piston) is very light whereas the secondary seal (around the primary) is darker and wider. They got it reversed.

CENTER: The OEM multi-layer stainless gasket. It only needs to seal 280hp so the engineers don’t seem too concerned with with a perfect band around each cylinder. However, you can notice that the clamping force is significantly higher than the Co…(oh shit sorry, no names, huh?) the gasket on the left.

RIGHT: The best of the bunch. The sealing area around the cylinders are round, consistent, wide, and the force is the highest. What does this mean to you? Proper cylinder sealing whether your engine is stock or you’re running 40psi boost on methanol with L19/H11/MP studs.

So next time you want to save a couple bucks and buy that cheaper gasket, don’t do it. You’ll be sorry you did. At the same time, there’s no need to break the bank for that over priced JDM gasket. Remember: JDM isn’t always the best choice. Have fun in boost (if you don’t have one of the gaskets on the left).

ADDED 10/19/07: I’m getting some emails asking me where to buy the Cosworth head gaskets. You can get them here at the XS Engineering site at less than retail price.

Leave a Reply

Your email address will not be published. Required fields are marked *