74sbZ Posted May 2, 2012 Share Posted May 2, 2012 Alright so here's the deal; I have a stock early 260z with a blown engine. It's a total loss so i need to replace it (obviously). So, I figured if I'm gonna spend the money on a new engine I might as well get a good setup. I've been searching and searching on here and other sites for weeks now while at the same time lurking Craigslist to see what's out there. While I was still gathering info I came across a mn47 for sale on craigslist and jumped on it just in case. The goal for the car right now is to get it running with enough power to be fun (as affordable as possible) and put the rest of what money I have into the suspension. I'm not looking to do any machine work or anything like that I just want to find a good combination of stock parts that will work together and be fun. I already have round top su's (and would like to reuse them in the interest of saving money) and a mn47 head and there's a guy locally selling a 75 280z engine that I could get the block from. My question is do you guys think this would be a decent cheap setup or would I be better of selling the mn47 and going a different rout? The threads I've read about the mn47 and flat top l28 have made me shy away from that, which is why I was thinking about going with dished... Any input/ suggestions are appreciated. Quote Link to comment Share on other sites More sharing options...
BluDestiny Posted May 2, 2012 Share Posted May 2, 2012 It will have a little more kick to it from uped compression but probably not a noticeable amount. I'd sell the MN47 to fund getting your car running, especially if you're only doing this temporarily. An mn47 should really have head work done to it. Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted May 2, 2012 Share Posted May 2, 2012 I was thinking of doing a mn47 an dished piston set up to keep compression down. But as I asked people on here they told me going that rout you don't take advantage of the quench pads on the mn47 head with dished pistons as you would with the flat top pistons. That set up is what I'm going to end up doing if I don't go with a n42 he's shaved set up. I will say this, look into higher octane gas in your area if you do flat tops with that head. If you have to spend money at least spend it on what you want, otherwise find a stock motor in good condition and run it till you know what you want. Do it right the first time Quote Link to comment Share on other sites More sharing options...
Leon Posted May 2, 2012 Share Posted May 2, 2012 (edited) The goal for the car right now is to get it running with enough power to be fun (as affordable as possible) and put the rest of what money I have into the suspension. I'm not looking to do any machine work or anything like that I just want to find a good combination of stock parts that will work together and be fun. Depends on your definition of "fun" I guess. I can have fun with 120whp from a stock L24. Find a running engine on CL and stuff it in. Shouldn't cost you more than a few hundred bucks and will get you on the road and having fun in no time! If you want to build an engine then buy a spare one and build while keeping the Z on the road at the same time. Edited May 2, 2012 by Leon Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted May 2, 2012 Share Posted May 2, 2012 The whole benefit to the MN47 is the quench that resists detonation......but only with flat top pistons. Now putting that head on a l28 with flat tops might be higher compression than the design works best with.........not sure. Quote Link to comment Share on other sites More sharing options...
74sbZ Posted May 3, 2012 Author Share Posted May 3, 2012 Alright guys thanks for the input. I guess ill just sell the mn47 and go with a stock l28 for now. That with the 4.11 diff I have will probably be good enough for now. Anyone wanna buy a mn47? Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted May 3, 2012 Share Posted May 3, 2012 Depends on your definition of "fun" I guess. I can have fun with 120whp from a stock L24. Find a running engine on CL and stuff it in. Shouldn't cost you more than a few hundred bucks and will get you on the road and having fun in no time! If you want to build an engine then buy a spare one and build while keeping the Z on the road at the same time. I'm just doing a light rebuild on my L24 and running it with triples. I won't be able to drive my car for awhile though since I'm doing a full restore. Listen to Leon and I get a motor to drive since you'll love driving your Z anyways right? Build a performance motor on the side. Your su's can be massaged a bit to give you some better performance to. Quote Link to comment Share on other sites More sharing options...
Gollum Posted May 3, 2012 Share Posted May 3, 2012 In theory you can use a dish piston with a MN47 while still taking advantage of quench, just not with STOCK dish pistons. You'd need something with a custom dish that's a smaller diameter dish circle. Quote Link to comment Share on other sites More sharing options...
Heroez Posted May 3, 2012 Share Posted May 3, 2012 I came across a mn47, and looked into it. Somewhere, maybe atlanticz.ca, that has the L engine calculator. You find out what combinations yeild. The thing I want to share is that the mn47 is like an updated e31. Its made for a 2.4 and should be modified to fit to the 2.8 by increasing the size of the head valves. This is machine shop work. So its not ideal, but I have heard people say it is the best single modification to a dished piston L28 in their opinion. Use the calculator. Quote Link to comment Share on other sites More sharing options...
Mack Posted May 4, 2012 Share Posted May 4, 2012 OH, myths and heresay! Depending on what sort of engine management you choose to run, the MN47 is an awesome choice for a flat top L28. I had almost all of the ping for pump gas tuned out running megasquirt with a stock cam. As I have told others, get some MILD head work done to the MN47, such as cleaning up the valve bowls and having the valves unshrouded, that will drop compression a bit and make some nice gains at the same time. KEEP the stock valve sizes, as the smaller intake valve combined with the high swirl design of the intake port and big compression gain (almost 2.5 pts!) will produce some nice down low torque numbers and street driving. It will add power UNDER the curve, where it counts on the street! If you run a cam it will lower the dynamic compression a bit and you can probably run pump gas ping free if you have a decent fuel and spark management system. I don't think I would do it with carbs and a point distributor. Another thing is that with that high of compression and that small of a combustion chamber, you won't need as much advance for optimal power as you would with a lower compression head. The flame front has less distance to travel, therefor you need less advance. I think a lot of people forget this fact when they ***** about the fact that you need to run less advance with this head to keep detonation under control. You also run less advance for optimal power. Aaaaaaaaaaand que the degeneration of this thread into an argument about quench....... (I hope not, though) Quote Link to comment Share on other sites More sharing options...
Heroez Posted May 6, 2012 Share Posted May 6, 2012 There is no arguement I see. The post was about combined stock parts, and avoiding extra machine work. Megasquirt, headwork, aftermarket cams are off topic but somehow relevant to the understanding, as well as being interesting. As long as you add your take on things, then you did your part, and the readers appreciate that. Quote Link to comment Share on other sites More sharing options...
74sbZ Posted May 6, 2012 Author Share Posted May 6, 2012 There is no arguement I see. The post was about combined stock parts, and avoiding extra machine work. Megasquirt, headwork, aftermarket cams are off topic but somehow relevant to the understanding, as well as being interesting. As long as you add your take on things, then you did your part, and the readers appreciate that. Agreed. Thanks for the input everyone. I found a rebuilt l24 with less than 5k miles on it for a steal. So the rotsun will be back on the road very soon. Quote Link to comment Share on other sites More sharing options...
Gollum Posted May 7, 2012 Share Posted May 7, 2012 There is no arguement I see. The post was about combined stock parts, and avoiding extra machine work. Megasquirt, headwork, aftermarket cams are off topic but somehow relevant to the understanding, as well as being interesting. As long as you add your take on things, then you did your part, and the readers appreciate that. I think the "argument" or "disagreeing views" is the valve size standpoint, as it was mentioned by someone earlier that since the MN47 has the smaller valves that you should replace them with the later Z motor large ones. And the end of his post was more about how every thread that mentions the MN47 seems to go up in flames like an on fire news paper with poo on it. It's never a pretty thing really. Quote Link to comment Share on other sites More sharing options...
Heroez Posted May 7, 2012 Share Posted May 7, 2012 That is why I still have an unused MN47. I havent found anything definate. I hope to see some dyno data on that head with small vs large valves. Quote Link to comment Share on other sites More sharing options...
Mack Posted May 7, 2012 Share Posted May 7, 2012 I did actually Dyno my car once, still running the stock electronics. I made 141rwhp at about 4100 to 4200 rpm, iirc. Apparently, I had a bad e1280 ignition module because the car absolutely refused to rev over 4500rpm. A friend of mine (1 fast Z) drove the car after the megasquirt conversion and he said it felt like a really solid, really low 15 sec car. Which, considering it's a 280ZX 2+2 slick top with AC and the stock 1/4 mile time is probably somewhere in the mid 17s, is no small feat for bolting on a head and megasquirt with some other BPUs. The set up consisted of an f54 flat top block, a fel-pro head gasket, a non egr 280ZX intake with injector bumps smoothed down, 60mm 240sx tb, mandrel bent where-the-cat-should-be back 2.5" exhaust and of course megasquirt, controlling spark through a 280ZXT dist with 280ZXT injectors. I have a cam (delta 280* or something close with maximum allowable valve lift on stock springs), a header, and a set of 40mm ITBs and the mn47 head is getting ported to match the intake. I plan on putting all that crap on the car this summer and having it re-dynod before I yank the engine and put in something a little more fun (like a turbo charged mercedes OM606). I hope to break into at least the 170s, maybe even 180s at the wheel. This head would make an excellent choice for a warmed over L24. We (1 fast z and I) measured the combustion chamber and it came out to be right around 39CCs. This is basically a better head than the E31. and it already has the bigger exhaust valves. Quote Link to comment Share on other sites More sharing options...
Perfect240z Posted May 8, 2012 Share Posted May 8, 2012 I have my mn47 waiting for me for when it's time. But I have a question about which block to use since I read and also chimed in on this thread. Is the mn47 head better for a L24 head or is it better for a L28... With or without work done? Quote Link to comment Share on other sites More sharing options...
Gollum Posted May 8, 2012 Share Posted May 8, 2012 You guys should also be keeping in mind that valve size is hardly a defining issue for a stock head in ANY case. Larger valves won't magically open up the breathing of the head. People assume it's the larger valves in the P79/P90 that makes them more power on their L24 block (once shaved and such to get the CCs back down). This is hardly the case. The later head designs were far superior in many ways and to look at just valve size is just plain ignorant. When having a head ported, YES run the largest size valve you can fit in there and make breathe. If I had a MN47 just sitting there any my only concern was weather or not to change the valve size I'd say GET THAT SUCKER ON AND RUN IT!!!! Too many people don't finish projects due to lack of bench racing to satisfy their wang before they get their arse in gear and do something. I'd rather learn from my own mistake but have a car on the road, than to never get something on the road because I'm still looking for flaws in my thinking. Quote Link to comment Share on other sites More sharing options...
Mack Posted May 8, 2012 Share Posted May 8, 2012 without work done, without a decent fuel and spark controller and some other things, I would not recommend the MN47 for the L28 block. SImply for the fact that the stock EFI and spark control doesn't have the tunability to keep detonation under control. The MN47, however, would make an excellent bolt on head for the L24. It will give you almost 10:1 compression with flat tops and a felpro head gasket as well as much better ports and combustion chamber design. Plus, you will be able to run unleaded gas without any other modifications, if you have a stock E31 or E88 on your L24. Gollum>>>> that is exactly why I swapped that head on in the first place. When I did do the swap, it was very uncommon and there was not a lot of info out there about it. But, I figured that since blocks and heads are (were) so plentiful and cheap for these cars, if I mess up something, the worst that could happen is it setting me back a couple hundred dollars and a weekend to swap the engine. That was something ridiculous like 8 years ago, and I would still be driving the car if I hadn't started taking it apart a few years back to convert the suspension over to S13 bits. and that project was severely sidelined.... eh, all in due time. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted May 9, 2012 Share Posted May 9, 2012 (edited) I ran a L24e with 280zx turbo stuff at 5psi for about 20,000 miles where it laid down mid 15 second quarter miles.......even after changing to a 3.54 from a 3.7 I ran the stock L24e system and injectors. Edited May 9, 2012 by HowlerMonkey Quote Link to comment Share on other sites More sharing options...
Noddle Posted May 9, 2012 Share Posted May 9, 2012 (edited) The MN47, however, would make an excellent bolt on head for the L24. It will give you almost 10:1 compression with flat tops and a felpro head gasket as well as much better ports and combustion chamber design. Plus, you will be able to run unleaded gas without any other modifications, if you have a stock E31 or E88 on your L24. I run a MN47 on my L24e ( dished pistons standard) with Turbo, Intercoolers, EDIS, 440cc injectors, MS 2 extra, switchable between 7, 10 & 15 PSi at a click of a button, runs very well.. Edited May 9, 2012 by Noddle Quote Link to comment Share on other sites More sharing options...
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