Bore to chamber match

[engineczar]

Any thoughts on what effect the alignment between the bore and combustion chamber has on airflow. Looking at a SBC 4.030 bore with Cast Iron Bowtie heads for a circle track application. With the heads bolted on the stripped block looking down the bores, the intake side of the chamber appears to sit about a 1/32 outside the bore. Would offset dowels correct the problem or should we look to clearance the top of the bores above the top rings. Same question concerning the exhaust side except that the chamber hangs into the bore.

Bill

[CNC BLOCKS]

We chamfer the top of the cylinders down to the top ring that has always worked fine for us on our house engines.

[EngineTech1]

If you're going to do a chamber you should scribie the bore outline onto the deck of the head and matching it to that. The steeper valve angle heads benefit more from this but the shallower angle heads don't usually need to be let out as far as the bore. Try moving the bore around on a flow bench sometime, .020 to .030 mismatch can make a difference in the way the port flows.

[CNC BLOCKS]

On all the engines we build we deshroud the intake side of the combustion chamber to a 1003 gasket or what ever we are using for a gasket and do the same on the deck of the block and our pistons the top rings are .180 down from the top to get a good chamfer on the cylinder.