How to Make More Horsepower With Your Cylinder Heads
Cylinder heads hold all the cards when it comes to making power. They determine how much air flows into and out of a vehicle's engine -- and making more power is a matter of increasing air flow.
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Instructions
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Have the cylinder heads milled to flatten the mating surface and reduce the size of the combustion chambers. Milling involves running a large, flat cutter over the cylinder heads' mating surface, removing a bit of material and moving the tops of the combustion chambers closer to the pistons. This can be good for as much as a half a point increase in compression, which will yield about a five percent increase in horsepower and torque.
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Install larger valve seats, and cut them so you can use larger valves. No matter what you do to your heads, the size of the valves ultimately determines how much air can flow in and out of the cylinder heads. Valve size is especially important for low-speed torque, since a large valve will help to increase air flow while preserving air velocity.
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Perform a full porting job on the heads. Almost anyone can gasket-match the intake ports to the size of the intake manifold gasket, and odds are you'll find the biggest gains in this area. Bowl-blending is equally important. It involves using a grinding stone or sandpaper cartridge to blend the valve seat into the cylinder head.
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Enlarge the overall dimensions of the port by about 1/16 of an inch using an assortment of sanding rolls, grinding stones and carbide cutter bits.
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Remove the pushrod pinch in the intake port by cutting it completely away with a carbide cutter bit. This will expose the inside of the intake port to the pushrod channel, which you'll need to seal. Drill the pushrod channels out by about 1/16 of an inch, and press 18-gauge chrome-moly tubes into the channels. Tack-weld the tubes to the heads to keep them in place.
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Coat the insides of your intake and exhaust ports with thermally insulating ceramic powder-coating. The powder-coating does a number of things, the most important of which is it keeps exhaust heat out of the cooling system and keeps engine heat out of the intake charge. Both of these contribute to engine power and longevity. It will also help to smooth out any hard angles or edges left in the ports, which enhances flow at low r.p.m.
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Tips & Warnings
Research the procedure before undertaking it. If you just start hacking away at the cylinder heads, odds are you'll either lose power or permanently damage the head. Re-working the short-side turn radius and cutting valve bosses offer huge potential gains, but can also be ruinous if you haven't done your homework.
