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The three main reasons for smoothing or polishing combustion chambers:
1. Enhances gas flow around the valve seat insert.
2. Removes hot-spots that can cause detonation and pre-ignition on high compression or forced induction engines.
3. Slows carbon buildup in the chamber.
There are also a few other small benefits.
You can do this at home using a dremel tool and part number 511 from your local Home Depot, or you can get small cross-buffs and a die grinder, but I found the dremel works well and is actually easier to use for the most part. The part 511 comes with rough and fine buffs. Just like with sandpaper you should start rough and work to fine. You will probably need 5-7 of these packages to do one pair of heads.
First, you need a spare pair of valves modified to be used to protect the valve seat from your abrasive finishing buffs. If you are not having a valve grind done, this will prevent any possible damage to the valve seat so you can simply lap the stock valves back in easily. You are going to need to grind down the margin thickness on these valves on order to smooth the areas of the chamber around the valve at all. This is simply the process of "Removing the Margin" from a stock valve on a bench grinder:
You should grind the face of the valve untilit sits below the level of chamber material when it is installed into the head.
This is your dirty little combustion chamber after cleaning it out very well with brake cleaner and a rag. These heads had under 80K miles on them, and look at the amount of buildup.
Now you can begin smoothing the chamber. First lightly round off the edge near where the head meets the block. If the heads have been resurfaced, this edge could even be downright sharp. You don't want to take very much off, and be sure not to hit the seal ring area outside of the chamnber much or you could affect the head gasket seal. Focus around any sharp edges, rough or porous casting, the seat inserts, and the spark plug hole.
Now you're on your way to being done with one chamber. You can use your same set of de-margined valves for chamber modifications for years to come. You can polish the chambers, but the only benefit over simply smoothing them out is that they may stay clean longer and better resist large amounts of buildup over the years.
1. Enhances gas flow around the valve seat insert.
2. Removes hot-spots that can cause detonation and pre-ignition on high compression or forced induction engines.
3. Slows carbon buildup in the chamber.
There are also a few other small benefits.
You can do this at home using a dremel tool and part number 511 from your local Home Depot, or you can get small cross-buffs and a die grinder, but I found the dremel works well and is actually easier to use for the most part. The part 511 comes with rough and fine buffs. Just like with sandpaper you should start rough and work to fine. You will probably need 5-7 of these packages to do one pair of heads.
First, you need a spare pair of valves modified to be used to protect the valve seat from your abrasive finishing buffs. If you are not having a valve grind done, this will prevent any possible damage to the valve seat so you can simply lap the stock valves back in easily. You are going to need to grind down the margin thickness on these valves on order to smooth the areas of the chamber around the valve at all. This is simply the process of "Removing the Margin" from a stock valve on a bench grinder:
You should grind the face of the valve untilit sits below the level of chamber material when it is installed into the head.
This is your dirty little combustion chamber after cleaning it out very well with brake cleaner and a rag. These heads had under 80K miles on them, and look at the amount of buildup.
Now you can begin smoothing the chamber. First lightly round off the edge near where the head meets the block. If the heads have been resurfaced, this edge could even be downright sharp. You don't want to take very much off, and be sure not to hit the seal ring area outside of the chamnber much or you could affect the head gasket seal. Focus around any sharp edges, rough or porous casting, the seat inserts, and the spark plug hole.
Now you're on your way to being done with one chamber. You can use your same set of de-margined valves for chamber modifications for years to come. You can polish the chambers, but the only benefit over simply smoothing them out is that they may stay clean longer and better resist large amounts of buildup over the years.
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