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Cometic MLS Gaskets - Combat Sealing
Why Multi-Layer-Steel Head Gaskets Offer The Perfect Defense For Boosted Engines
Ford SVT uses Cometic MLS gaskets on the '03-'04 Mustang Cobras. Paul Svinicki from Paul's High Performance has a lot of experience with supercharged Cobras. He says the MLS gaskets are a godsend. With some Cobras pushing 25 pounds of boost, he has seen few problems. Paul does not reuse the gaskets. "With all the labor involved in removing a head on a Cobra, the savings just don't justify the risk," he says. Other parts will fail before the head gaskets give out, so make sure you're on top of your tune-up
Have you ever found a product and thought I wish I had that back when? In these days of 15-psi-supercharged street blowers and 300hp nitrous shots, the technology found in modern head gaskets is a blessing. In the not-so-distant past, only big-name engine builders and dyno shops could afford Horiba wideband oxygen sensors. Most Mustangers didn't have a clue where their air/fuel ratios were. Needless to say, the learning curve was steep and many head gaskets were changed.
Once chassis dynos began showing up in every major city, people were able to have their cars tuned to safe levels. Still, head-gasket failures continued. The thin-wall-casting blocks with aluminum heads were prone to twisting and head shift while making power. This was hard on gaskets that were intended to lock or grip a head and deck surface. Many had initial success with the gaskets featuring built-in O-rings, but soon they proved inadequate as power levels grew.
The next popular solution was the graphite composition gasket. Apparently it was designed for two surfaces that had some movement. The graphite composition gasket proved reliable at lower boost levels. I had used them in my naturally aspirated Factory Stock engine with no problems. Extra time was needed during teardowns, however, in order to remove the graphite material from the mating surfaces.
When I made the switch to the 5.0 Mustang & Super Fords Real Street class in 2003, I wanted the best head gasket for a boosted environment. There were several considerations. The gasket had to be able to reliably seal the combustion chamber-with about 17 pounds of boost and a thin-wall block that wasn't going to be easy! It also needed to be something I could tear down and not have problems with assembly at the track. A reasonable price wouldn't hurt either-there is a budget to consider. With teardowns, testing, and freshening, I go through about 12 sets of head gaskets a year. At about $45 per set retail, that adds up.
With the 0.035-inch quench rule in the Factory Stock and Real Street classes, a predictable "compressed" gasket thickness is a necessity. The rules dictated that the piston be no closer than 0.035 inch from the cylinder head. In an effort to maximize compression, we ran the piston 0.010 to 0.012 inch out of the cylinder. With 71/416-inch ARP bolts torqued to 80-85 lb-ft, we measured the gasket at 0.048 to 0.050. I assume that the 0.042-inch advertised was measured using 11/42-inch bolts at 110/120 torque numbers.
The only change in the Real Street engine was to install a copper O-ring in the deck of the block. I have never been comfortable with receiver grooves in heads, due to the small sliver of aluminum that remains between the combustion chamber and the O-ring. That said, I had only one gasket failure in 2003. That was during testing after the finals in Bowling Green. I wanted to lean on the tune-up and found that we were actually fairly close all year. It burned past the O-ring and pushed the fire ring out about 11/44 inch-not bad, but just enough to drop power and heat up the coolant.
While in the pits at a Mustang race in Cordova, Illinois, I saw something interesting. Bill Rimmer was removing the head from his Pro 5.0 racer. The head gaskets he was using were Cometic Multi Layer Steel gaskets. Mark Wilkinson of RaceCraft explained that MLS gaskets were the hot ticket in high-boost applications. He also said they would be cleaned and reused. I could not believe what I was hearing! A reusable head gasket?