grinder11

iTrader: (1)

I have a couple questions I want to run by our forum members/head porters. Question A: Say you have $2,500.00+ invested in your heads (Not too hard to do) and you need new valveguides installed. Would you send the heads in to the head porter to R&R the valveguides, thereby having the guides "port matched" to the original port contours as they were when new, or, B: R&R them yourself and know there might be some reduction in port flow due to the guides not following the port as precisely as the originals, which were smoothly blended in to match the port work? Is this reduction in port flow substantial enough to be a concern, or is this not enough to be a legitimate concern? It would seem that if the heads we are talking about were CNC ported when new, you could, and probably should, return them to the company who did the port work. They could then set them up on the CNC milll and run the program they did originally, and the heads would be as good as new-VERY QUICKLY. In CNC machining, repeatability, accuracy, and reduced time in the machining operation are one of the big attractions of CNC machining!! Seeing as how I am a journeyman tool and diemaker with over 30 years in the trade, I feel that I can speak with some authority on this subject. While I am NOT a master head porter, I AM very knowledgeable in how they can set-up these machines and after the first program is written, the heads can be ported quicker than many people can imagine. I am also aware that if we are talking about HAND ported heads, it may cost a considerable amount money-because of the considerable amount of time- involved in re-producing the original "contour match" of the guide to the rest of the port wall, as compared to the CNC programmed machine. I am keeping my car for a very long time, and I am sure that those of you who are doing likewise will agree: With the aggressive cam lobe profiles and the stiff valvesprings required to effectively utilize these lobes, valveguide wear WILL come into play at some point in time. I, and I am sure some of the other forum members, will be anxiously awaiting the responses that this thread is sure to produce.

grinder11

iTrader: (1)

tttasap

grinder11

iTrader: (1)

C'mon, guys. Someone must have "been there, done this"!!

UGotBeaT

id have them installed by someone who knows what they're doing and then honed to the proper clearances and be sure the valve job is still concentric to the new guide. I wouldnt worry about reblending the guides back into the guide boss in an application like yours. It may take up a little more cross section if any but nothing to worry about as long as its the same length or close to what it originally had.

Jason99T/A

iTrader: (21)

Send them back to the person who did the work originally. Anytime you change guides, you need to re-valve job the heads. A valve job can make or break a set of heads.

Jason

grinder11

iTrader: (1)

Thanks to all who posted up. I DID do exactly that, and sent them to AFR. I called them this week and talked to Tony. He said, and agreed with, one other post here. He has flowed heads both ways, with and without "blending" in the new guides to an already CNC'ed port, and told me that it only amounts to 1 or 2 CFM, max. You can't tell the difference. Problem solved, question answered!! Thanks, again.