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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?
You're probably saying, "I run copper head gaskets. They are reusable." Sure they are, but as you know, you need at least one O-ring and at times a receiver groove depending on the application. The copper head gaskets also require cleaning and prep work before reuse. You have to spray them with a sealer, let them dry, then install the heads. Before reusing them, they have to be cleaned, along with the heads and deck. The time savings alone makes the MLS gaskets a huge plus.
With plans for a new Real Street engine in 2004, I wanted to check out the Cometic MLS gaskets. While in Las Vegas for the SEMA show, I met Bob Gorman, the owner of Cometic Gaskets. Naturally, he gave me a thorough education on his product. After talking to Bob, I felt as if I'd been living under a rock. It seems that MLS gaskets are used a lot in imports and high-horsepower, small-displacement applications. Warren Johnson uses them in his Pro Stocker, so they must be good enough for Real Street.
As it turns out, these gaskets are beneficial in several ways. They are avail-able in a variety of thicknesses, they are reuseable, and they require no machine work to the block or cylinder heads. Several racers in the NMRA Renegade class have made the switch to Cometic gaskets. These MLS gaskets have eliminated the head gasket as the weak link. Other parts will fail before the head gaskets give out, so make sure you're on top of your tune-up.
The Postman Torques Twice
In my search for information, I discovered that NMRA EFI Renegade racer Mike Post used the Cometic MLS gaskets during the '03 season. If you follow the Renegade class, you know these guys change their head gaskets like socks. Some racers in Renegade just aren't happy if they don't have the heads off at least twice during a racing weekend. With more than 28 pounds of boost and no intercoolers, these cars are time bombs.
Mike has been using the Cometic MLS gaskets for about a year and has several observations. He says that when the gasket is starting to "push," you can see the inner steel layer between the cylinder head and block surfaces. He described a change in the way the engine sounds. Always pushing the tune to the limit, Mike knows what the engine sounds like before it lets go. He has let the engine cool down between rounds, dropped a degree of timing, and gone as many as three rounds.
The real beauty is that Mike says when he pushes a gasket with too much timing, he just cleans and reuses it. The Cometic MLS does not require retorquing, but in the heat of eliminations, Mike will retorque the bolts near the affected cylinder as a precaution.
Since I switched to the Cometic MLS gaskets, my experience has been positive. We tested two sets of heads on the engine dyno and reused the Cometic head gaskets. After we tapped a valve in Bradenton, we had an opportunity to look over the gaskets. The seal between the cylinders and water passages held up well. We will clean and reuse the gaskets for our next race in Reynolds.