When you take an engine engineered to provide reliable, grocery getter performance, then modify it up to push out 400, 500, or 600 horsepower, you’re going to uncover some weak points. This is often revealed in the head-to-block sealing.
It is a problem that, up to this point, is without a good solution. With sky-high cylinder pressures and not much meat in either the block or the cylinder head of cars like the Honda Civic (the most popular subject of modification), head lift, combustion leakage, and subsequent total loss of sealing have become an accepted fact for many speed demons in the import world.
They bolt on the turbochargers, plumb in the nitrous, and hit the strip. The short answer is that these engines can’t be sealed effectively at this level of performance.
Sean Devine is owner of Maxwell Automotive, an independent repair garage in Mississauga, Ont., and proud owner of a sub-12 second 1993 Honda Civic. The 1.6 SOHC V-TEC in the hatchback came with 125 bhp stock, but courtesy of a turbocharger and nitrous, now puts more than 350 hp to the front wheels. Consequently, he is well aware of the sealing problem, but has developed a novel approach: he chooses not to address it.
It’s not a case of ignoring the problem. He just sees it as the lesser of two evils.
“Most of the guys who I know that are into more power than I am still run stock head gaskets. They O-ring the head and the block. I don’t do that. On a personal level, I’d rather blow a $50 gasket than blow a block. So if something goes, it’s usually the gasket instead of the block,” says Devine.
“When it comes to racing I try to look at it as a big picture. I would rather replace the gasket than the whole motor, but on the other hand I’m not making as much power as the other guys.”
The “other guys” he is referring to are putting nearly 700 hp to the wheels, and when they blow, it’s more than a head gasket that needs replacing. “Usually rods and something else will come through the block,” says Devine.
“It’s just unending. You fix one problem and you create three in the chain. When we first started, we used to crush pistons, so we bought performance pistons. Then it was rods, and we got performance rods. Now it’s up to head gaskets. You just keep going.”
He says that some competitors have taken to machining the face of the block to leave a step around the cylinder, forcing more clamp load onto the gasket. This can lead to increased block and head distortion, but it is a halfway solution in a world where that’s about as good as it gets.
This is not to say that gasket suppliers haven’t been working on the problem, though.
“We’ve been looking at Honda and Mitsubishi,” says Jim Daigle, Fel-Pro product manager at Federal-Mogul’s Skokie, Ill., gasket facility. “[Product engineer] Joe Hermanson and I were at a Honda shop recently and the guy was getting some crazy horsepower numbers. Right now, they’re using OE gaskets. They’re having some success, but we think there are some things we can improve on.
“They all seem to have head lift problems–especially with the horsepower numbers they are putting out. It’s incredible to me that the bottom ends are staying together. Certainly there is an opportunity, especially with the Mitsubishi, because it seems to have more problems than the Honda.”
Getting a handle on what is required is difficult, because there are no standard performance parameters. Pick a performance level and it will probably be exceeded no matter how high you aim.
“Cylinder pressures are probably around the 1,200 to 1,500 psi range,” says Hermanson, explaining that is about double stock figures. “But it depends whether they are using nitrous, whether it is turbocharged, and whether they have some abnormal combustion going on,” he adds. I offered that the answer to all three was usually yes. “Then you’re spiking even higher,” he replies.
In fact, some estimates put peak pressures at up to 3,000 psi. Just not for long.
“We don’t have really any performance gaskets for those applications,” says Rick Pacyna, product specialist, Victor Reinz Gasket, Dana Canada Inc. “I think in the future, we’ll see a lot more high performance gaskets for the Honda. I’m sure that with the market growing the way it is, it is probably an avenue we are going to fall into, but it takes a while to engineer those gaskets.”
“It’s an interesting area,” says Marty Novil, director of static sealing at Corteco. “What’s really gone on is that those engines are extremely hard to seal. It’s almost like the old days of American hot rodding. These days you can seal American engines easily, but they’re not making the kind of horsepower per liter the import performance guys are.
“The result is there is lots of head lift. No gasket is going to last very long. There is combustion leakage all the time. It affects performance a little, but they have so much that they don’t even notice it until it blows up.”
The analogy with classic American performance may not hold at first glance, but the quarter-mile performance figures, 11.5 E.T. from a Honda Civic in “mild” tune, or into the 9.0 second range for the extreme approach, from a street engine, is something to behold.
“It’s a beautiful thing,” says Novil with enthusiasm. “I feel that if I worked with one of those guys, we could probably get a gasket to work. But we probably wouldn’t want to sell it because we wouldn’t want the liability of saying that it works.”
He does have a suggestion, however, but it is only for those who are prepared to pay for the consequences if it doesn’t work. It involves constructing a custom multi-layer-steel gasket.
WARNING: THIS IS AN EXPERIMENTAL APPROACH. IF YOU TRY THIS AND IT DOESN’T WORK, YOU ARE ON YOUR OWN.
“The interesting thing about the MLS gaskets that most of these engines are equipped with is that each layer accommodates 5 to 8 microns of lift per active layer,” says Novil. “You could construct a gasket with more active layers if the hot rod guy knows which is the active layer and they are truly aligned correctly so they don’t nest.” The result should be a gasket that can accommodate the head lift that is occurring and still spring back to provide a seal.
Again, with all necessary caveats, Novil says that it should be possible to take two MLS gaskets apart, set up a system of dowels to ensure that the bores and galleys are very accurately located, and produce a gasket with enough active layers to accommodate the head lift encountered in these engines.
He doesn’t know if anybody is doing this so it remains a theoretical approach, but perhaps one worth looking into.
For most, it is simply a case of being vigilant and changing head gaskets often. In racing, says Novil, it is expected that you might have to change a head gasket every few hundred kilometers. This may seem excessive for a street-to-track machine, but short gasket life is the price for running so much horsepower.
“There’s no way to say that they are going to make a reliable, streetable head gasket when they are pumping out that much horsepower.”