rags Posted August 20, 2006 Share Posted August 20, 2006 Well the time has come to get serious about making some power. My short block consists of a 3 liter config using a diesel crank 240 rods and custom Ross flat top pistons that are 1mm down in the bore. Currently I am using a P90 that is bone stock. Power is pretty good but I know it can be a lot better. I am planning on sending a head to Paul (Braap) to have some work done. My question is which head? I'd like to get as many ideas as possible before getting started. For the head choice, I'm open for anything. The only thing I don't want to do is touch the bottom end. I know I'll get a lot of flack for having pistons with flat tops that are 1mm in the hole but there was a reason for doing it that way and so it stays. I guess I shoud say that this config gives a cr ratio of 8.5 to 1 when using a P90. Any Ideas guys?? Joe Quote Link to comment Share on other sites More sharing options...
AK-Z Posted August 21, 2006 Share Posted August 21, 2006 Is it turboed? IMO I would keep the P90 if it is. If NA or with you want more compression, the P79 would be the easiest way. Have read the the n42 and n47 heads are good but would need to be milled to stop knocking with that much compression. Quote Link to comment Share on other sites More sharing options...
rags Posted August 21, 2006 Author Share Posted August 21, 2006 Yes it's turbocharged. The reason for the piston choice was so I could use the bottom end for a 8.5-1 turbo motor with a P90 or a 10.2-1 NA motor with an E31. I'd like to concentrate my efforts on getting a head to flow and minimize detonation with flow characteristics. Joe Quote Link to comment Share on other sites More sharing options...
Guest 280ZForce Posted August 21, 2006 Share Posted August 21, 2006 i'd stay w/ the p90 and just did some work done to it. have your manifolds port matched to it though for best flow. i have a 3.1L stroker turbo motor. you can read my sig or click my cardomain for the rest of the specs. Quote Link to comment Share on other sites More sharing options...
AK-Z Posted August 21, 2006 Share Posted August 21, 2006 Lol. For some reason I didn't read the title when I posted last time. Maybe I should stay away from the keyboard at 3 in the morning lol. Well the least amount of work would be the p90 head since you already have it, (I think I stated that earlier. I have gone to sleep yet, lol). Don't recall what some of the differences are beteen the p90 and the p79 except the compression and chamber size. Quote Link to comment Share on other sites More sharing options...
rags Posted August 21, 2006 Author Share Posted August 21, 2006 Thanks Jason. Have you done any port work on your head? And if so, how much did the boost drop after the porting? Right now I run between 15 and 16 pounds on a T04E/T3. I've never had the car on the dyno and I know it can be tuned for more power. I use a TEC II and the car runs pretty good but I am far from a tuner! I'd love to learn from somone how to tune the TEC but there really isn't anyone in my area that knows how. Or I just haven't found them So now it's trial an error. Quote Link to comment Share on other sites More sharing options...
rags Posted August 21, 2006 Author Share Posted August 21, 2006 AK-Z, See that's my dilema. I have a few E31's, a few P90's, a P79 and an E88. I want to start out with the right one that, with the right work, will give me the best results. I guess I'll also be changing the cam so if anyone has had good luck with a specific grind, I'm all ears. Oh and AK, don't worry about the posting while you should be sleeping thing. We all do it Joe Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 21, 2006 Share Posted August 21, 2006 P90 and P79 have the same combustion chamber size and shape. With the piston 1mm below the deck there will be no quenching effect, so there will be no extra detonation protection. You should had made a piston that had a D shaped dish to allow the flat top of the piston to come out even with the deck height where the head is flat. 0.040" is the the biggest distance that quenching will work. And 0.040" is the head gasket thickness, so you need a true flat top, even with the deck height, to get it to quench. FYI, stock turbo engines or any dished piston Z do not have any quenching either. A P90 or P79 will make 8.6:1 cr a N42 or N47 will make about 10:1. Use a P90 for a turbo or a N42 for a NA build. Quote Link to comment Share on other sites More sharing options...
rags Posted August 21, 2006 Author Share Posted August 21, 2006 Hi Pyro, Yep, I agree with everything you say. Unfortunately, I have what I have when it comes to the pistons. Do you think there is anything that can be done to the shape of the chamber to increase the swirl characteristics to decrease the chances of detonation? So far the only thing that I'm sure of is the use of a P90 seems like the way to go. Joe Quote Link to comment Share on other sites More sharing options...
Pyro Posted August 21, 2006 Share Posted August 21, 2006 I wouldn't worry about the quench too much since there is nothing you can do about it now. However, I would get a EFI system that has ignition timing control. Being able to shape the timing curve will do wonders for power, anti-detonation, and mpg. The timing curve is just as important as the fuel curve, especially with a high compression turbo engine. 8.6:1 is high compression for a turbo as far as datsuns are concerned. You should be able to easily run 10 to 12 psi on 93 octane with 8.6:1 cr with a good efi system. And even more with some racing fuel when you take it to the track. Quote Link to comment Share on other sites More sharing options...
rags Posted August 21, 2006 Author Share Posted August 21, 2006 Although there are better EFI systems now, the TEC II is doing ok so far. I can get 15-16 pounds of boost on 93 octane albeit running pig rich! Joe Quote Link to comment Share on other sites More sharing options...
vegasnative Posted October 2, 2006 Share Posted October 2, 2006 hey, did you make up your mind ? i would like to know as im in the place with my turbo/stroker setup Quote Link to comment Share on other sites More sharing options...
rags Posted October 2, 2006 Author Share Posted October 2, 2006 Hi Vegasnative, yep, I'm using a P90 again. Joe Quote Link to comment Share on other sites More sharing options...
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