Some of you guys have probably been through this already, but some, like me, have not. So, I have a few questions for you guys, and your opinions are valuable to me. Because of the modern cam lobe profiles we have today for the LSX motors, and the stiff valvesprings required to fully utilize these aggressive lobe profiles, valveguide wear WILL come into play if you own your car/motor long enough. Hypothetical situation: If you had a set of CNC ported heads, and the guides needed replacing, would you send the heads to the CNC head porting company who did them originally, or R&R them yourself/locally, knowing the guides you or your favorite local shop press in WON'T match the contour of the port wall as closely as they did when they left the CNC machining center when new? And, of course, if they were sent to the company who did the CNC job originally, I would think that they should come back with the new guides matched to the contours of the port wall as smoothly as when they ported them when new. Or.... is the difference in flow so minute it is not worth worrying about? I feel that if the porter went to the work (And you spent the money) of blending the guides into the port wall in the first place, then it must have made a worthwhile difference in port flow. I know that through the years I have seen/read that this "blending" in the "bowls" makes quite a difference in flow, so it would seem that if they came from the CNC machine/porter blended into the port wall, they should be re-blended if, and when, the guides are replaced. I realize that if the heads were hand ported, this would cost a considerable amount of money-because of the considerable amount of time, and work-needed to re-match the guides to the ported contour of the port wall. But on a CNC machine, the program that the company originally ran when porting your heads could be run again, and it would take VERY little time to do this job. Now, I admit I am NOT a master head porter. However, I AM a journeyman tool and diemaker with over 30 years in the trade, and I feel that I can speak with some authority on the subject of CNC machining. That is the beauty of CNC machining: repeatability, accuracy, and less time spent machining the product. It would seem that if the company that did the original CNC port work would re-install the program for your heads, the machining itself would only amount to removing a VERY slight amount of the valveguide, and not any, or a VERY small, amount of head material. Certainly not the huge amount of head material removed when they started on the unported heads you bought originally. I am sure that the responses that this thread generates will interest many of us on the forum. I know I am anxiously awaiting them.

 

C'mon, guys!! Surely someone has been in this situation before, haven't they?!

 

I assume that you're speaking of the 225 AFR's in your signature. Give Tony Mamo a call and discuss your situation. He's a straight-up guy and he won't lead you astray.

Steve

 

AFR IS where I sent/bought my heads, and you are correct that they ARE the 225's in my sig.. I called Tony this week and asked him. He told me that he has flowed these heads with-and without-the "blending" of the guides, and found only 1 or 2 CFM difference at the most. Not enough to worry about, unless maybe you are going for a national record, or something, and even then D/A would most likely make a bigger impact on power than this minute amount of flow difference. Thanks for posting up.