I am currently building my 996TT tiptronic engine and trying to decide if I should port my heads. I do not want to do a full $5k+ head job as I do not plan to rev past 7k (tiptronic).

Has anyone else just ported their heads and used the oem valves springs etc.. ? If so, please post some details.

Thank you!

 

At least do a little bowl blending and cut down the valve guide on the intake side. Also have the air ports in the exhaust ports tapped and plugged. Keep the heat out of the head.

 

I know I am not the OP but I am really interested by your replied. Tim can you be more specific about the suggestions. Bowl? cut down the valve guide ? and the air port in the exhaust ports tapped and plugged. Thanks!

 

If I had my heads off I think I may do a precision 3 or 5 angle grind on the seats and a light reface on the valves, possibly back cut them as well. I'd check the seat to port interfaces especially on the intakes and eliminate any steps and a general cleanup. I'm not familiar with the Turbo heads but I recently saw some Subaru WRX heads with the valves out and they looked like they could be improved a lot. I'm not sure how much good cleanup on the Turbo heads would do as it's a pretty slow reving motor. I've done a lot of headwork on 13k to 16k+ 4-5 valve motorcycle heads for roadracing and it helps a lot.

 

On the intake side the valve guide extends past the port. the added support in not needed. 997TT has this stock. On the exhaust side the extra length helps pull the heat out of the valve. The valve pocket can use a little blending in the area where the port ends and the bowl area begins. The air injection ports in the exhaust valve pocket can be plugged off and that will keep the heat of the exhaust from backing up into the head. If you think the exhaust does not get up there then explain how all the carbon gets into the head? The added heat is no good anyway you try to slice it. Pulling the heat out of the head is free power.

 

Thanks Tim for the clarification.

 

You know my opinion on heads. curious if any opinions on intake plenum port matching or extrude hone.

 

Use the 997.1TT halves. They are a high velocity port design that also helps to direct the air charge to ride the roof of the port. That is why the intake valve guides are cut down on the 997 heads. 997 and 996 ports are the same.

 

Its funny you say this because I was talking to a guy at Champion Motorsports and he said whatever you do to your heads just be sure NOT to cut off the part of the guide that extends into the port.

I am not saying your wrong (i know next to nothing about this stuff), its just funny.

BTW...You have any videos of your car doing a run Tim?

 

Generally speaking, shortening the valve guides decreases their support thereby accelerating wear. In a motor built for competition, longevity in the valve stem and guide may be sacrificed for slightly better flow. Where wear should be as long as possible and flow impeded minimally, generally the full length of the guide is retained but the area that extends into the port is reduced in size by turning in a lathe prior to installation, thinning and streamlining while installed or both.

I cannot see where shortening the extended area of the guide would have no ill effects on wear except if the valve stems and guides were overly long to begin with offering more support than what was actually needed. This may be the case, but then has me wondering why the additional length in the first place?

I know every little thing that can be done on N/A motors in the way of making a smoother and less obstructed path through the port and into the combustion chamber while keeping velocity high pays big dividends in the way of power as rpms rise. I don't know how this plays in a boosted motor. I assume it's a factor but to a much lesser degree. It would be very interesting to do some dyno testing with a heavily ported head, vs stock vs one that was made to flow slightly worse than stock under boost with no other mods done.

 

I can not upload a pic right now but you are removing only 3-4mm. What is the fuss? plus it is only on one side. Ben, I do not video myself driving but others have.