dj paul Posted December 13, 2005 Share Posted December 13, 2005 Alright, i have a rebuilt 280zx turbo p79 head (without hydrolic lifters), an N47 head (that would need rebuild), and e31 head(need rebuild). previously i had seen/thought/found that the p79 head would have the best flow characteristics due to its turbo nature, on a turbo motor. i found (just on one site) but am just making sure, that the n42 head is the most disireable head. Im building a L28 motor with flat top pistons NPR Intercooler t3/t4 .63 trim turbo Megasquirt with custom fuel rail and delivery system. im guessing the compression would be around 9:1 with p79 on flattop? 9.5-10:1 with E31 and like 8.5 with n47? tell me if im wrong but am i correct in thinking the rebuilt p79 would be the best for my set up? P.S. Yes i have searched =) thanks in advance, paul Quote Link to comment Share on other sites More sharing options...
Thumper Posted December 13, 2005 Share Posted December 13, 2005 The turbo head is a p90 or p90a head. The p79 came off of the 280zx n/a engine. For a turbo application the p90 is the best because of the exhaust ports matching up with the stock exhaust manifold. For an n/a application the n42 head is better because it will raise the compression ratio and it has a better exhaust ports over the earlier e88 head. Here is more info good luck. http://geocities.com/zgarage2001/ Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted December 13, 2005 Share Posted December 13, 2005 Hey DJ paul, Thumper is right the P79 was only on NA heads. your CR's are a little off P79 with flattop = 8.52:1 E31 with flattop = 10.21:1 N47 with flattop = 9.82:1 if you used the the P79 with a 1mm HKS(steel $200 ) head gasket you can get the CR up to 8.71:1 I got these CR #s from the Lengine calculator it's an awesome program. The P79 is the one that I would go with it suposedly flowes the best and it will give you the best CR for a turbo application. the E31 would be a disaster, It has the small valves, not good for a larger displacement (2.8 vs. 2.4) short block, not to mention the 10.21:1 CR way to high for a turbo IMHO. The N47 is a great head but why bother when you have the P79. The link that thumper put down is awesome this site has great info too http://geocities.com/row4navy/head2.html Good luck and let us know what you go with. Rock on Z people P.S. if you want the Lengine calculator just google it. Quote Link to comment Share on other sites More sharing options...
dj paul Posted December 13, 2005 Author Share Posted December 13, 2005 im sorry guys, the head i have is a p90 head without the hydrolic lifters. after sifting through a bunch of info somehow about all the casting numbers and what was different, i led myself to believe that i had a p79 the info you all gave me was still very helpful. the p90 would be best choice? i just dled that lengine calculator http://flzclub.com/downloads.htm if anyones interested, its pretty cool. my cr is going to be around 8.7:1 . anyone happen to know how much boost i would be able to run with my setup? Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 13, 2005 Share Posted December 13, 2005 my cr is going to be around 8.7:1 . anyone happen to know how much boost i would be able to run with my setup? All depends on your fueling and your sparking! To little fuel, BOOM! To much sparkie advance, BOOM! This is independent of CR, this goes for any turbo application. Get your fueling right and you will be supreised how high your boost level can go! Without you specifying what flowrate injectors you will be using, nobody can tell you! Quote Link to comment Share on other sites More sharing options...
dj paul Posted December 14, 2005 Author Share Posted December 14, 2005 oh ok. lol. im not exactly sure yet, any recommendations? this is a weekend/track/fun car and i want around 275 rwh or more. and, thanks, again =) Quote Link to comment Share on other sites More sharing options...
AK-Z Posted December 14, 2005 Share Posted December 14, 2005 im sorry guys, the head i have is a p90 head without the hydrolic lifters. after sifting through a bunch of info somehow about all the casting numbers and what was different, i led myself to believe that i had a p79 the info you all gave me was still very helpful. the p90 would be best choice? i just dled that lengine calculator [url=http://flzclub.com/downloads.htm]http://flzclub.com/downloads.htm[/url'] if anyones interested, its pretty cool. my cr is going to be around 8.7:1 . anyone happen to know how much boost i would be able to run with my setup? All p79 had normal lifters, the p90a were the only heads that had hydrolic lifter. I wouldn't get a p90a for its lifters because its just one more thing to go wrong. Those lifters were only made to lower the noise of the engine. The reason why not enough fuel and/or too much advance on boost will make your engine go BOOM is because gasolene is in a way a coolant. When you compress air into a tiny area it cause it to heat up, now the more oxgen compressed the hotter it can get. now add a little gas and BOOM. Now adding more gas replaces some more of the oxigen that would be compressed. NOw I'm confusing myself, lol. Now if can understand what I was tring to explain, I'll be surprised. Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 14, 2005 Share Posted December 14, 2005 I wouldn't get a p90a for its lifters because its just one more thing to go wrong. And to beat the dead horse: "NOT ALL P90A's WERE HYDRAULIC LIFTERS!" Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted December 14, 2005 Share Posted December 14, 2005 Im going to be running 9.2:1 CR ??:. From all the reading i've been doing, and believe me it's a lot, as long as you keep the air fuel raito right, along with a "great" intercooler and great engine computer (megasquirt or simillar) you can run enough boost to make your car go 0-60 in holy$hit. I plan on starting with 7lbs of boost to start ... and I'll turn it up untill I sence(this is where my spidey sences will come in handy) there is a problem or 12lbs which ever comes first. Keep us updated with your progress Rockon Z people Quote Link to comment Share on other sites More sharing options...
Tony D Posted December 14, 2005 Share Posted December 14, 2005 10 psi is where my wife drives the car. I drive it on "high boost" setting 15+ For 12psi, there will be few troubles! Even with stock turbo injectors if you boost the fuel pressure to 45psi. You may want to source some 440CC or 370CC/min injectors for better pulsewidth on the top end. And they are far from being too big for decent idle. Quote Link to comment Share on other sites More sharing options...
dj paul Posted December 14, 2005 Author Share Posted December 14, 2005 p90a was with hydrolic lifters p90 is without i have the p90 lol! "spidey senses" i wish i had those. the car blows up before i realize i over did it. ill try getting a hold of those 440cc injectors those would be good up to 18 psi if i wanted?? or would i need 500cc? and thanks again everyone, and yes, ak-z, lol, i could get what you were saying (for the most part) Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted December 14, 2005 Share Posted December 14, 2005 Hey TonyD, do you run 15+ lbs with stock CR or are you putting that much boost through 9 or higher CR? I'm trying to build a beautiful, somewhat stock 240Z that will KILL just about any stock "sports car" on the road. Rock on Zpeople Quote Link to comment Share on other sites More sharing options...
dj paul Posted December 14, 2005 Author Share Posted December 14, 2005 like we were saying, you can, you just need the fuel to do it with a good intercooler. but im eager to hear what cr as well. Quote Link to comment Share on other sites More sharing options...
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