PhaTTy Posted April 21, 2003 Share Posted April 21, 2003 Hello.. I currently have a P90 head on my 280zx N/A .. I believe this head has very low performance when not being used in a turbo setup. I was wondering if it would be worthwhile to have my P79 head rebuilt or try to find a N47 and rebuild it. Just want opinions on what is better, and if I change over the the P79/N47 head, are there any mods that anybody would recommend. I was thinking of dropping a performance cam in it as long as I will be rebuilding it, but am not engine savvy so would like some recomendations on what would be best for a daily driver with some good low-end - mid-range power. I would be willing to shave the head or do whatever is recommended since you guys I am sure have done this sort of thing before. Thanks for your time and hope to hear from you soon. P.S. - Is there a good increase in performance if I would stick a performance ignitor/coil/wires/etc.. on also.. It just seems to be lacking the power I would like right now and I am sure lots of stuff is wore out and needs attention. Quote Link to comment Share on other sites More sharing options...
fl327 Posted April 21, 2003 Share Posted April 21, 2003 p90 requires a lot of shaving to up compression ratio enough to have NA punch, which also requires you to shim the cam towers and a couple other steps to ensure valve train geometry. p79 and n47 will bump up power if you dont do a cam or anything else, my move is to put an n42 head with a small backyard port job on it, i believe you will get a 9.8 or higher compression ratio with it and it will run pretty good, should bolt on too. if i were doing NA i would use f54 block with flattops and a n42 head and intake with modified L jetronic system. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted April 21, 2003 Share Posted April 21, 2003 The P79 has the same combustion chamber volume as the p90. The N42 has less chamber volume, so it will give you more compression UNMODIFIED. If you mill the head, I would use the P79 or P90, but if you do not know how to set up a head and shim the cam towers and all that mess, this is best left alone. There are several threads on this subject in the archives, and I would suggest you look them up, if the search function is working. I have a less then popular view in that I think the P series heads are the best, but don't want to get that mess stirred up again. The bottom line is the easiest way to make more power is to use the N42 and rasie your compression. Maybe mill it 15 thousandths just to true it up. Quote Link to comment Share on other sites More sharing options...
PhaTTy Posted April 21, 2003 Author Share Posted April 21, 2003 OK.. The block in the car is the F54 but am not sure if it has flat tops or not in it (1983 N/A GL) .. If it does have the flat-tops, the N42 is sounding pretty good to me so far. As I said before I am not an experienced mechanic so as much details as I would need to tell a machine shop or my dad (experienced mechanic) to do to a N42 .. would be much appreciated. Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted April 22, 2003 Share Posted April 22, 2003 That should be a flat top engine, and it will give you some compression with an N42. Mild cam and header with exhaust, and you are good to go. Good luck. Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 22, 2003 Share Posted April 22, 2003 I just finished building a NA L28 with an F54 block and N47 head (round port). CR should be around 10:1 with stock head gasket (flat tops). I hope to get it started in the next month or so. I'll be putting it on the dyno, so I'll post the numbers when I'm done. Pete Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted April 23, 2003 Share Posted April 23, 2003 Maxima head, or Z head? And did you mill it? I thought the N47 had pretty large combustion chambers. Are you sure its not an N42? Quote Link to comment Share on other sites More sharing options...
PhaTTy Posted April 23, 2003 Author Share Posted April 23, 2003 I believe the head I am referring to is the N47 (am not sure, but my brother has either the N42 or N47 on his '76 280z and it will throw you back in your seat) .. Anyway, maybe someone can clear up which one it is that I want. Quote Link to comment Share on other sites More sharing options...
z-ya Posted April 23, 2003 Share Posted April 23, 2003 Both the N42 and N47 have the same size combustion chambers. The N42 has square ports, the N47 has round. I think the N42 is probably a better choice, but I picked up a rebuilt N47 cheap. Pete Quote Link to comment Share on other sites More sharing options...
Lockjaw Posted April 23, 2003 Share Posted April 23, 2003 Well the head with the square ports on the exhaust is generally regarded as better flowing, although that is a whole new thread. N42 is what you probably want. Quote Link to comment Share on other sites More sharing options...
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