Eric Posted December 3, 2005 Share Posted December 3, 2005 does anyone have experiance with these? MSA says they are flat top with a bit of a dome. how well would my stock 77' take to that? are they even worth buying? from what i understand, the 83' had a 10:1 compression. would i be better off just using that head and forgeting the pistons? i've done a bunch of reading about heads and compression but i'm still a bit confused. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted December 3, 2005 Administrators Share Posted December 3, 2005 NO, those pistons wouldn’t do you any good with your ’77 head, and also of note, none of the OE L-series engines came from Nissan with 10:1 compression. There is a FANTASTIC thread 3 pages long about heads, compression ratios, all with different L-series heads. Your best bet is to read this thread first… http://forums.hybridz.org/showthread.php?t=104420&highlight=Big+Nasty Good luck, Quote Link to comment Share on other sites More sharing options...
Eric Posted December 4, 2005 Author Share Posted December 4, 2005 NO' date=' those pistons wouldn’t do you any good with your ’77 head, and also of note, none of the OE L-series engines came from Nissan with 10:1 compression. There is a FANTASTIC thread 3 pages long about heads, compression ratios, all with different L-series heads. Your best bet is to read this thread first… http://forums.hybridz.org/showthread.php?t=104420&highlight=Big+Nasty Good luck, i gess the person that told me the 10:1 wasn't very well informed, i'm still learning alot about these cars so i can't distingwish(sp?) some of those things yet. i've read that thread and still strugle with understanding it all. hold on a sec. BRAAP says that the MSA pistons won't do me any good, but DAW, u'r saying that i'd have to high of compression. that is, if i'm reading right. i'm pulling the motor out tomarow to run a rebuild. it'll be out for a week or 2 so i'd have time to track down a diff head. Quote Link to comment Share on other sites More sharing options...
AK-Z Posted December 4, 2005 Share Posted December 4, 2005 Well I think its a matter of how much work you want to put into it. The problem you will have with higher compression is that it will eventually start "pinging" (predetination). That is caused by not enought fuel mixture and/or too much heat in the chamber. Fuel in this case is also used as a coolant, in a way, to cool the chamber enough and as a ignition fuel. So more fuel for higher compression. There are a couple of ways of "adding more fuel." One would be getting a new engine computer. With a car almost 30 years old, you wouldn't think that the electronics of yor would be as efficient as today. Another would be to install carbs instead of fuel injection. Less efficient than FI , as in fuel economy, but get the job done and a little more easier in obtaining more power than fiddleing with engine computer settings IMO. Last and possibly the easiest solution would be to just install bigger injectors and/or raise the fuel pressure in the lines. Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted December 4, 2005 Administrators Share Posted December 4, 2005 Eric, I apologize for mudding the waters. What I meant to say is that those pistons won’t work for your 1977 N-47 L-28 cylinder head. DAW post clarified what I was saying with little more detail, (thanks DAW). To repeat what DAW already has posted, the P-79 and P-90 heads share the same combustion chambers. The Naturally aspirated Z cars, 1981-1983 ran the P-79 head from the factory with flat top pistons. The turbo cars ran the P-90 head with dished pistons to lower the comp-ratio even further, but the combustion chamber of the Turbos P-90 is the same as the no turbo P-79 head. These pistons that you mentioned have a slight dome to raise the compression a little more than stock in this application. One of my customers, (now a great family friend, Mike Hintz) is running those exact pistons in his L-28 and his old engine builder though the earlier N-47 would be ideal with these domed pistons and with 92 octane super unleaded and a mild Crane cam, he had detonation issues that could be heard at higher RPMS outside of the car when he passed by at WOT and also showed up very clearly on the dyno. I convinced him to let me build him a P-79 head and go back to a stock cam and after putting it all together and re-tuning the EFI and ign advance for this combo, (OE L-jet EFI and ign), he couldn’t be more happy. The engine ran WAY smoother, pulled harder everywhere in the RPM band, (on the dyno showed a 10 ft lbs increase over the previous set up across most of the rpm range with solid 15 HP increase at peak), and best of all, no more detonation. He is wanting to switch over to standalone EFI and at that point we may put the Crane cam back in as we then can tune around the new VE curve the Crane cam delivers, (can’t really tune the OE EFI around different cams other than OE cams). That is whole other topic. Sorry for going off on a tangent. In short, those domed pistons are a direct replacement for the 1981-1983 280-ZX L-28E flat top pistons for the naturally aspirated engines. If you put those pistons in an earlier L-28 you also need to find yourself a P-79 or P-90 head as either of these will compliment the domed pistons very nicely. Just don’t use those domed pistons with your 1977 N-47 head or any of the other earlier heads unless you plan to run Race or Av gas in the vehicle. Also, AK-Z made some good points as well in regard to help curbing pre-ignition and detonation. Carbs offer the ability to make several other mods rather easy, (as does “stand alone EFI†like SDS, Megasquirt, Electromotive, etc). A richer fuel mixture runs cooler which helps keep detonation at bay if you on the edge, but in the case of my friends car, richer wasn’t enough. He just lost power and the detonation was still there. Even if you don’t understand the physics behind “why†you need to certain heads with certain pistons, just trust us that do understand the “why†and you’ll do just fine. 90% of the guys posting here on topics as in depth as these do know what they are talking about from experience, not just hearsay or theory and it is rather easy to weed out the posts from those that are just guessing or applying only theory to their posts. If anyone else sees any holes in what I was trying to convey to Eric, please feel free to jump in and fill in those holes… Quote Link to comment Share on other sites More sharing options...
2003z Posted December 4, 2005 Share Posted December 4, 2005 Even if you don’t understand the physics behind “why†you need to certain heads with certain pistons, just trust us that do understand the “why†and you’ll do just fine. 90% of the guys posting here on topics as in depth as these do know what they are talking about from experience, not just hearsay or theory and it is rather easy to weed out the posts from those that are just guessing or applying only theory to their posts. So I've got a L28ET block with dished pistons and P90 head, running NA with SU carbs. The car won't go above 4800 rpms under load. I was considering flat top pistons and an earlier head (I forget which one Eddie Radatz was recommending to me yesterday), but reading this, it seems like I could go with these pistons and keep my P90? Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted December 4, 2005 Administrators Share Posted December 4, 2005 Yes you could. The flat tops and your P-90 head is a fantastic mild street combination. Your engine should still be able to run above 4800 RPM even with the low compression which tells me something else is amiss, ie. Ignition timing, fuel mixture, or cylinder sealing, (head gasket, rings, or valves not sealing). At any rate, Flat tops or the slightly domed pistons discussed here would be ideal for your naturally aspirated set up. Good luck, Quote Link to comment Share on other sites More sharing options...
AK-Z Posted December 5, 2005 Share Posted December 5, 2005 I think its the length of the connecting rods that they are refferring to. You don't want the top of the pistons to raise over the top deck of the block, then pistons will hit the head causing all sorts of things to break. Quote Link to comment Share on other sites More sharing options...
evildky Posted December 5, 2005 Share Posted December 5, 2005 we have a local guy running dometop pistons, and shaved P90, mild cam and untuned ebay webbers that just dyno'd 170whp (mustang dyno) with about 11:1 on 93 octane pump gas Quote Link to comment Share on other sites More sharing options...
Eric Posted December 5, 2005 Author Share Posted December 5, 2005 thank you for for clearing that up BRAAP. it sounds like that P-79 or P-90 are just what i'm after. my dad and i just pulled the motor today and it'll be in the shop getting rebuilt for a few weeks. that will give me enough time to find one of those heads. Quote Link to comment Share on other sites More sharing options...
Guest Dorifto Posted December 5, 2005 Share Posted December 5, 2005 I see you're in Washington ... I'm in central Utah, so not too far away. Anywho, I've got a P79 head, maybe we can work something out. PM me if you're interested. Quote Link to comment Share on other sites More sharing options...
Eric Posted December 5, 2005 Author Share Posted December 5, 2005 i'll keep that in mind if i deside to bore it. if it doesn't need to be bored then i'll just go with the euro's and a P-79/P-90. thanx for all the imput everyone. Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted December 6, 2005 Share Posted December 6, 2005 Hey Eric, as if you didn't have enough to consider... I did a build up with an F-54 block .20 overbore flat top pistons, N-42 head and a 2mm HKS head gasket. using the L engine calculator I figured that gave me 9.2:1 CR. I'm running SU carbs with SM needles, I also have a schnider cam 460 lift 270 duration. It's a really fast little N/A engine, spins up to 6500rpm, with power in the blink of an eye, and I don't have detination problems on 91 oct. It's great fun to drive and it was an easy, "cheap" build. I have no idea what it's HP #'rs are but but Im ready for turbo. With the engine that I have, I should be able to run about 12lbs of boost safely with the proper engine management and IC. What I'm saying is ... think about the future.... turbo will become more and more interesting. Good luck with your build and let us know what you do. Rock on Zpeople P.S. If I had it to do all over again I'd build a straight up turbo... you just cant get the kind of HP with a N/A engine that you can with a turbo. If you think you don't know enough to build one, this site should inspire you. 3 months ago I didn't even know how a turbo worked ... thanks to this site I just rebuilt a Nissian Z31 T3 turbo. You can do it! This site can help! Quote Link to comment Share on other sites More sharing options...
Eric Posted December 6, 2005 Author Share Posted December 6, 2005 i've toyed with a lot of engine ideas since buying the car. i was planning to get this motor set up to run turbo later on(would run a higher compression head in the mean time). out of all the swaps i've thought about, turbo L28 and sbc have been the most appealing. and after carefull deliberation, i've desided to go back to my roots and get a sbc. but i'm not gona do that till much later, if i ever get to it. i just figure while i'm rebuilding this motor(240k, dying), might as well do some cheap hp gains. yes this may seem impractical to some, spending $$ on a motor i'm just going to get rid of, it fits my situation better at this point. Quote Link to comment Share on other sites More sharing options...
Eric Posted December 14, 2005 Author Share Posted December 14, 2005 Another option would be if you can get a set of oversized flatops, say 0.060" for '81-'83 280ZX (non-turbo) and overbore the block and run a P90 or P79 head...I didn't crunch the numbers but you'd end up with more displacement and a higher c.r. than the stock 8.8:1, probably 9:1 or so, more if you shave the head a bit...you may end up with just a little more money in it but end up with more power than the std size L28E Euro pistons. DAWi was playing with the Lengine calculator and that combination came out at 8.79:1. but it said that stock was 8.29:1. i trust what all of you have been telling me, i'm just a bit thrown off by the difference in numbers from the Lengine calculator. Quote Link to comment Share on other sites More sharing options...
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