4znova1 Posted March 29, 2007 Share Posted March 29, 2007 i have heard the p-79 is the same as the 9-90 with the exception of round exhaust ports with runners. Should the runners be removed? will there be a difference in flow, if so how are they removed? Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted March 29, 2007 Administrators Share Posted March 29, 2007 Yes, the P-79 is very close to the P-90 in port design and EXACT in chamber design, with exhaust ports being the prominent difference between the two. In regards to the exhaust liners, you can spend the multitude of hours removing them, but if mega exhaust flow is your goal, you would be much better served just finding a P-90 head and porting the exhaust port by removing the step in the roof. Trust me on this. For mild to hot street applications, the round exhaust ports with the liners intact are more than adequate and offer great flow. Just blend that sharp edge from the back side of the valve seat to the liner using a die grinder or dremel tool. If you want to really make it worth your while, you need to unshroud the valves as well. I wont go into details in this post, but if you perform a search, the details and pics are here on this forum… hint (BRAAP has posted pics with the how and where to remove material… ) Quote Link to comment Share on other sites More sharing options...
steveosupremeo Posted March 29, 2007 Share Posted March 29, 2007 Paul, doesn't the P79 also have the "D" shape in the intake ports? on a Maxima N47 i noticed this and used a dremel to make a smoother transition where it humps up. i also noticed the step in the roof on the exhaust port of the P90a i'm working with and was wondering why that was even cast there. if i do any porting for the turbo setup i'm going with it will be to grind that down. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted March 30, 2007 Administrators Share Posted March 30, 2007 Paul, doesn't the P79 also have the "D" shape in the intake ports? on a Maxima N47 i noticed this and used a dremel to make a smoother transition where it humps up. i also noticed the step in the roof on the exhaust port of the P90a i'm working with and was wondering why that was even cast there. if i do any porting for the turbo setup i'm going with it will be to grind that down. Stevo, Yes, you are absolutely right. The P-79 intake port does have “slight†D shape where as the P-90 is pretty much non existent, but you can just barely see a small flat on the inboards port wall. The Maxima N-47 has a VERY Pronounced D intake port, WAY more than pronounced than any of the other late heads. As for the cast step in the exhaust port, I am not totally sure, and the only explanation I can offer is that it is there for valve guide support and to help carry heat away from the exhaust valve as it is closer to the valve head. Here are a couple pics of a P-90a head that we built for a hybrid member across the pond. i have heard the p-79 is the same as the 9-90 with the exception of round exhaust ports with runners. Should the runners be removed? will there be a difference in flow, if so how are they removed? To save you some searching, here are a few good L-series head threads… Lots of good “meat†to chew on in regards to L-heads… http://forums.hybridz.org/showthread.php?t=104420 More good meat to chew.. http://forums.hybridz.org/showthread.php?t=105653 L-head mods, DIY http://forums.hybridz.org/showthread.php?t=110269 Quote Link to comment Share on other sites More sharing options...
steveosupremeo Posted March 31, 2007 Share Posted March 31, 2007 mmmmmmmmmm.....shiny.....hehe...thanks for the insight Paul, i also have a P79 laying around that i haven't really studied much. might have to take a peek at it. right here lately though i robbed the nice clean valves off of it for my P90a head whose valves were so nasty i decided to scrap. used the time serts for solid lifters and used JB weld in the oiling holes. and its not easy getting that stuff to drip down in those tiny holes but it was about 85 degrees so it did thankfully, lol. also i enjoyed those links myself. thanks, Stephen Quote Link to comment Share on other sites More sharing options...
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