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Old 02-20-2017, 09:55 AM   #113 (permalink)
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Originally Posted by craysus View Post
With exhaust and inlet mods... Are significant gains being found with porting and Port matching along with extrude honing... Or are after market manifolds readily available that could be used?
Does anyone have measured gains with just those mods?
Surely the oem didn't get the manifolds so bad out of the factory that big gains are available?
I'm not going to try to port (changing the shape with a hand grinder imo is a bad idea), but polishing casting imprfections would help airflow. Port matching gasket and manifold conections could help airflow. I don't know about the manifold on the big Cummins motor, but the cast iron exhaust manifold on the isb leaves alot on the table for improvement. Here's a good read.

Exhaust System Technology: Science and Implementation of High Performance Exhaust Systems
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