Thanks to Gary Morrell.
What it is
Extrude Hone is a patented process where a putty that is loaded with various grits of silicon carbide abrasive is forced through intake runners and/or cylinder head ports to smooth and enlarge the passages to improve their flow characteristics. The process removes all casting flash and all traces of the original sand cast core finish. I just had the intake done for now. EH hones the short and long runners, and then does some hand smoothing in the throttle body plenum, surge tank, and crossover plenum areas. The plenums and surge tanks do not lend themselves to the EH process because the pressures involved might split the large cross- section castings. Besides, the benefits would be negligible. The normal cost for this service is about $585 plus shipping. Preparation means completely dismantling the manifold and removing all the sensors and attaching hardware. Basically, you ship them only the castings.
The end result, after honing, according to flow bench tests, is that the runners flow about 20% more air for the same pressure drop.
How effective is it?
Ted Breaux's observations: The only way to effectively gauge the effectiveness of extrude hone on a SHO is to do a before and after with a clean manifold. A person or two has reported a positive difference after honing their intake runners. I noticed NO difference. I began with a CLEAN manifold. I also know that if you have a dirty manifold (just about everyone) and clean it, there is usually a perceptible difference. Extrude honing may just be a very expensive way to clean your manifold where the SHO is concerned.
You can contact Extrude Hone at 562.531.2976.