Guest Anonymous Posted December 23, 2000 Share Posted December 23, 2000 OK guys, before I go V8 I want to build a nice NA L6 engine for my Z car. It is just something I want to do. I have decided not to go turbo but, when that craving hits, I will then go V8. The ideal configuration I want is: P90 head, NA motor, approx. 9.5:1 CR, no shaving, no tower shims. I have been playing with the engine calculator I got from Clint. The best I can come up with is L28 crank, L28 rods, L28 flat-top pistons, bored .040 over, P90 head, FelPro head gasket. This gives a theoretical CR of 8.9:1 (better than stock) and the deck height is good. The configuration I really like is the same as above but with the diesel crank and dished L28 pistons. The CR is now up to 9.4:1. PROBLEM: deck height is +2mm. This is where my experience stops. This is my first engine rebuild past stock specs. You know, the first "tweeked" motor. I just don't like the idea of tower shims. I have been told that someone could weld some metal on the flat tops for configuration#1 in order to get the CR up a little higher. All of this makes sense to me THEORETICALLY but I need real world experiences. Bring it on! Quote Link to comment Share on other sites More sharing options...
jeromio Posted December 23, 2000 Share Posted December 23, 2000 Seems to me the guy who's had the most success with the NA L28 is Norm 12sec Dual SU over at zcar.com (which you obviously already know about). Seems to me he mostly recommends a high CR L28 without the expensive LD crank, although that's what he currently runs (along with an N42 head I think - I'm sure a quick search at zcar would reveal his exact specs). He apparently "machined" the tops of his pistons using sand paper and a flat floor! So, maybe config #2 and shave the dish off of the pistons? As far as welding metal on top of the pistons, man, that just sounds way scarier than some tower shims. Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 23, 2000 Share Posted December 23, 2000 Yeah, I had read about Norm. He has done some great things. The motor that I build is going to be fuel injected and I do plan on getting a management system for it. I don't want much over 9.5:1 CR because I don't want to have to worry about the gas I am running or pinging and detonation under varying conditions. I want to build it soundly, put in in and get the normal wear out of it. I think Norm stacks a couple of head gaskets and such, though. I don't want to do that, either. I guess shims would be OK. I know that it is commonly done. I had even been told that pistons could be made reasonably. I do have to buy flat-tops anyway. I will, of course, research all of the options further but I wanted to see if anyone had a solution or suggestion. Craig Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 23, 2000 Share Posted December 23, 2000 Sand paper and a flat floor? The man has patience thats all I have to say... Lone Quote Link to comment Share on other sites More sharing options...
Drax240z Posted December 23, 2000 Share Posted December 23, 2000 If you have the money for it, probably the best way to raise compression is to have pistons made specifically for your head. ------------------ "Gimme Fuel, Gimme Fire, Gimme that which I desire" -Metallica Drax240z 1972 240z - L28TURBO transplant on the way! http://members.xoom.com/r_lewis/datsun.html http://members.home.net/drax77/newpage.html Quote Link to comment Share on other sites More sharing options...
Evan Purple240zt Posted December 24, 2000 Share Posted December 24, 2000 Okay let me play now hehe.... Ideal-Z, heres my thought on the subject. You say you are going to run aftermarket FI correct? well.. if thats the case feel free to build a 10 to one motor. You can easily run pump gas with that setup and the adjustablility. Second, if you dont plan to keep the motor in the car for along time i wouldnt reccomend buying custom pistons. Just get standard flattops. No sense wasting your money! Okay are you dead set on the P90? I would really reccomend the N42. The head gives a good CR and flows pretty darn well. Whereas the P90 is great for turbo because of its being setup for not detonating. To put it in a nutshell. IF you really want a v8, dont put too much money into your NA L motor. Just doestn make sense and you will end up eating quite a bit of that money if you want to sell the motor later on. If i were to do another NA motor, i would not go stroker. Norm has taught me alot, and one of those pieces of knowledge is that the stroker isnt the key to HP, but is the key to your wallet! I guess thats all i have to add, i am pretty darn knowledgeable on the NA motors. I spent ALOT of time and money on my last motor looking for high HP numbers. Learn from my mistakes!!!!! Good luck dude!- Evan PS im sure you can pick up an N42 for less than you can sell that P90 for!!! Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 24, 2000 Share Posted December 24, 2000 OK. Looks like I knew what the answers were all along. Thing is, I have 2 P90 heads and 2 N42 heads already. I guess I must abandon my attempt to use the P90 on an NA motor. I do plan on keeping the L6 that I will build. The V8 attempt will most likely be in a second Z car. My Dad is probably going to get in on the act so all of this may be something that we do together. Dad has been a domestic car guy his whole life but he is REALLY starting to like the Z cars! Looks like my options are to use the N42 or have pistons made for my P90 application. All depends on the $$$ I want to spend. Stroker is only something I will do if I can get the stuff reasonably and I have no intentions of going to 3 liters. Thanks guys. Craig Quote Link to comment Share on other sites More sharing options...
Guest Anonymous Posted December 25, 2000 Share Posted December 25, 2000 Buy my engine already! n42 head, nismo flattop pistons, schneider cam, etc, etc, etc. 10.5:1 compression ratio. Low miles, already built, and has those fancy schmancy weber carb thingies! I'll be in birmingham either late this week or sometime next week picking up my turbo if you wanna see the engine and stuff. ------------------ Morgan http://z31.com/~morgan/s30 http://carfiche.com Quote Link to comment Share on other sites More sharing options...
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