Selasa, 01 Maret 2011

Cylinder Head Porting

Now that we've got a good understanding of air-flow, we can move on to cylinder head porting. If you haven't yet read our article on the basics of cylinder head porting and air-flow, I'd suggest you do so now as it provides the foundation for understanding what we want to achieve with the actual cylinder head porting.


Before we can get started, we need to strip down the cylinder head; remove the camshafts and camshaft pedestals, then remove the valves, valve springs and valve stem seals. You should also remove all manifold studs. With everything stripped, you need to inspect the cylinder head for cracks. It's no good porting a cracked cylinder head, though a cracked cylinder head may still be good for experimenting on, so don't throw it away! The most likely areas where cracks will appear are between adjacent valve seats, and around the valve seats, especially around the exhaust valve seats. You may need to some emery cloth to remove any carbon deposits to do a thorough check.

If you don't see any cracks, have the cylinder head thoroughly cleaned in a chemical bath. You can dip a cast iron cylinder head in a hot caustic solution but don't dip an aluminum cylinder head in it! Caustic solution will react with the aluminum and give off an explosive gas! For an aluminum cylinder head you should use Trichloroethane. If you don't have access to a chemical bath, you can use engine cleaner and a stiff brush to get oil and gasket pieces off. Once the cylinder head is clean and dry, use a sand blaster or a wire brush to clean off any stubborn carbon deposits. Once that's done, do another thorough check for cracks.

If you don't see any cracks, have the valve seats replaced and the valve guides removed by a reputable engineering shop. Replacing the valve seats are not crucial as long as they're in a good condition. However, you must have the valve guides removed.

WARNING: Take care when working with a grinder. Adhere to the following safety precautions when porting cylinder heads and using a grinder in general:

  • Wear eye protection when working with a grinder; goggles are advisable but a full face visor would be better.
  • Wear a dust mask or a respirator; inhaling metal filings is harmful.

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