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August 26, 1996
Cure Chronic Head Gasket Failure with a 351W Conversion
One of the largest problems nitroused or boosted Mustang enthusiasts face is the constant threat of blowing head gaskets. The late model 302 block is a thin wall casting, this conserves weight and is less expensive for Ford to cast, but poses a serious problem when cylinder pressure is substantially increased. The block flexes and distorts under stress, which in turn allows the cylinder head to lift and place uneven pressure on the head gasket. The result, the head gasket will generally rupture into the coolant passages.
Many cars that aren't even going that fast or creating much cylinder pressure have problems keeping head gaskets in tact. We've found the primary cause being detonation in between gears while power or extremely quick shifting.
There are many preventative steps that can be taken to try and prevent detonation. Make certain you're fuel system is up to the delivery task and you have a large enough injector. Keep your timing conservative, it's better to go a couple tenths slower than replace head gaskets on a regular basis. Run a high octane racing fuel, think of the added cost as an insurance policy. Racing fuel will allow you to safely run more aggressive timing, and therefore make more power. Use head studs or high quality bolts, both do a much better job of holding the head in place than the factory torque-to yield bolts. O-Ring the heads or use Fel-Pro's Loc Wire gasket, both are excellent ways to decrease gasket failure, but neither are fool-proof with the thin wall block.
We've built cars that are identical to one another, some have problems with head gaskets, some don't. Driver error and low octane pump gas can account for a majority of the head gasket failure we see. Too many people stay into a run when they hear a little detonation and others don't hear it at all, and just a "little" is all it takes. Many of the quicker cars that don't have gasket problems are very light, and don't need to make as much power or run as hard as heavier cars. And often it's the way the block was machined at the plant. We've seen brand new blocks that didn't have perfectaly flat decks, this will lead to nothing but head gasket failure. Parallel decking and squaring a block when it's out for a rebuild is a must for gasket integrity and is a substantial help. But the fact remains that the block is inherintly weak and prone to flexing.
If you're not on a tight budget, a Motorsport A4 block will solve almost all these problems. But for most racers, a 351W is a better choice and is one of the most effective and cost efficient ways we've found to alleviate chronic head gasket failure.
A 351W may at first seem like a radical change, but it's not that difficult or expensive. A 351W Lightning shortblock is only $1350 and you only need a few other parts to complete the swap, an oil pan, headers and lower GT-40 intake (assuming that's the intake you're using). If you're using a Vortech don't worry, we make a 351W Blower Bracket that places the compressor in the perfect location, hood clearance is not a problem and all other accessories bolt up in their stock locations.
Even the late model 351W blocks, which are also thin wall castings, are significantly stronger than 302 blocks. The sheer beefiness of the 351W block prevents it from flexing, this is what eliminates head gasket failure. In addition to the added strength, the extra 49 cubic inches will yield a substantial increase in power and torque once the combination is sorted and properly tuned.
Some racers may be concerned with the strength of the hyperutetic pistons used in the Lightning shortblock. You don't need to be. The pistons are more than strong enough for most applications and have proven themselves to hold up under high boost and nitrous use, providing there is no detonation. Detonation can prove fatal to even forged pistons, so the hyperutetics are certainly not immune.
We've been running 351W in a number of cars, including our own low ten second '88 LX. The results have been exciting to say the least. At the Ford Motorsport Nationals we detonated the engine hard enough to break the ring lands on two hyperutetic pistons, but the tear-down showed two Fel-Pro "Blue" head gaskets that looked as good as new. The gaskets sealed so well that they actually left ring impressions in the aluminum TFS.
Replacing your 302 with a 351W is an excellent way to cure chronic head gasket failure and increase power substantially, without going broke.
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