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2ndGenTeg · 01-13-2002, 02:49 AM

By now, everyone is pretty familiar with my favorite saying: If it was all that great, Honda would have done it in the first place.

-The combustion chambers in the head will have to be machined to accomodate an 86mm bore. While this isn't a huge problem or really especially costly, it does present another problem. It increases the size of the combustion chamber. Combine that with the B16A's or B17A's relatively short stroke, and getting a piston dome high enough to generate a respectable compression ratio starts to look pretty big. This creates two problems. 1: Valve to piston contact becomes an issue with any high dome piston used in conjunction with any high lift/ long duration camshaft. Survival here depends on a good valvetrain and knowing when to say when and not getting too aggressive when choosing a compression ratio. At 12.5:1, it should be safe, and pump gas would still be an option. Good tuning of the valve timing and an experienced engine builder will also help immensely. 2: A high dome piston isn't all it's cracked up to be. Sure, generally the higher you go with compression, the more power you can make. However, once the piston dome becomes too high, you start to run into combustion issues. Think of the combustion wave as it is first ignited in the chamber. With a smaller or flat dome piston, the combustion wave has a much easier, much more direct route across the piston and combustion chamber. The higher the piston dome gets, the more it is in the way of this combustion wave. For these two reasons, I wouldn't go above a 12.5:1 compression ratio with this engine. The piston dome would simply have to be too big to be practical.

-When I first started exploring the possibility of boring the cylinders, I talked to many people who had bored theirs out to 84mm. The first question I asked was why stop there? Why not keep going to 86? 90? Larger? The largest you can bore the stock cylinders is 84mm. Any larger than that, and the cylinder walls become too thin. So what about sleeving? When working with a larger bore application and sleeved cylinders, you can only go so far before from above, the cylinders begin to look like an Audi logo. The achilles heel of the engine has now become the head gasket, and the space between the cylinders. To remedy this, a thicker head gasket is necessary (further increasing our dome height problem), and strong head studs (such as the ARP) to reduce flex.

01-13-2002, 02:49 AM	#4
2ndGenTeg 4th Gear Join Date: Aug 2001 Location: Boulder, CO Age: 44 Posts: 830	The Disadvantages By now, everyone is pretty familiar with my favorite saying: If it was all that great, Honda would have done it in the first place. -The combustion chambers in the head will have to be machined to accomodate an 86mm bore. While this isn't a huge problem or really especially costly, it does present another problem. It increases the size of the combustion chamber. Combine that with the B16A's or B17A's relatively short stroke, and getting a piston dome high enough to generate a respectable compression ratio starts to look pretty big. This creates two problems. 1: Valve to piston contact becomes an issue with any high dome piston used in conjunction with any high lift/ long duration camshaft. Survival here depends on a good valvetrain and knowing when to say when and not getting too aggressive when choosing a compression ratio. At 12.5:1, it should be safe, and pump gas would still be an option. Good tuning of the valve timing and an experienced engine builder will also help immensely. 2: A high dome piston isn't all it's cracked up to be. Sure, generally the higher you go with compression, the more power you can make. However, once the piston dome becomes too high, you start to run into combustion issues. Think of the combustion wave as it is first ignited in the chamber. With a smaller or flat dome piston, the combustion wave has a much easier, much more direct route across the piston and combustion chamber. The higher the piston dome gets, the more it is in the way of this combustion wave. For these two reasons, I wouldn't go above a 12.5:1 compression ratio with this engine. The piston dome would simply have to be too big to be practical. -When I first started exploring the possibility of boring the cylinders, I talked to many people who had bored theirs out to 84mm. The first question I asked was why stop there? Why not keep going to 86? 90? Larger? The largest you can bore the stock cylinders is 84mm. Any larger than that, and the cylinder walls become too thin. So what about sleeving? When working with a larger bore application and sleeved cylinders, you can only go so far before from above, the cylinders begin to look like an Audi logo. The achilles heel of the engine has now become the head gasket, and the space between the cylinders. To remedy this, a thicker head gasket is necessary (further increasing our dome height problem), and strong head studs (such as the ARP) to reduce flex. Last edited by 2ndGenTeg : 01-14-2002 at 01:57 AM.