MN47 head preperation

[Xnke]

I recently obtained a cylinder head core from the parts yard, an MN47 head, that I am going to piddle with. I don't *need* the head, and it is truely a core at this point, although all the valves seal up just fine. The rocker posts have been donated to another engine and I'd have to replace them with other posts (I have other posts, but the ones in this head were chosen for a few reasons), as well as remove a snapped off exhaust stud from the #1 exhaust stud position. This head is also very slightly out of true; I measured 0.004 thou of warp. Very, very little water jacket corrosion. Other than the slight warp, and the busted stud, the head appears to be a good canadate, there is very, very little core shift that I can find.

 

I am planning to remove all the threaded in core plugs in the head, remove the valve guides, and strip the head completely to a bare, machined casting, and work through the preparation of a competition-grade cylinder head, best I can figure. I am not sure I want to yank the valve seats at this point in time, although they will be changed to fit larger valves, if it appears that larger valves will help with port flow. Since this head has the steel exhaust port liners, I do not think I will achieve proper competition grade performance, but finding an E30, Y70, or 05L head casting is only a continent away. (Honestly, I think the Y70 cylinder head is the best starting point for a head that wouldn't be allowed to be welded.)

 

I am also seriously considering leaving the head alone, refitting the rocker posts, and trading it straight across for an N42 head to do the exact same process to.

[roger280zx]

The N42 has more absolute flow potential. But, depending on your needs, that mn47 is a damn good head. My friend's 3.1 dyno'd 217 hp at the wheels with a braap ported mn47 with STOCK Maxima valves! I don't recal the torque numbers, but it is damn responsive and tourquey. The set up includes tipple 44's, a pretty big racer brown cam, and a Nismo header. I have read that the exhaust liners conribute a lot to street drive scavenging, all though they do sacrifice some top end flow. My friends build shows that they are not a bottle neck at these power levels and neither are the little Maxima valves.

[Xnke]

Been scrubbing the head down this evening, and last night too. Layed a headgasket over it and there isn't much room in there to unshroud the small valves as it is...going to a larger valve looks like it would shroud the valve curtain area more. I'll talk to my machinist to see what he thinks. (He used to do port work, but got tired of the folks coming in with crap cores and wanting them to flow like aftermarket CNC port jobs)

 

It'll be a long term project, this is not a top-of-the-list project.

[Oddmanout84]

Guess I'm not the only one messing around with a 47 head "just cause" right now...

 

 

Still a lot of work to do, only have a single carbide bit and my trusty dremel to work with.

[Xnke]

Mn47 and n47 heads aren't the same...but that's a heckuva nice polish in that chamber!

[ozconnection]

I recently obtained a cylinder head core from the parts yard, an MN47 head, that I am going to piddle with. I don't *need* the head, and it is truely a core at this point, although all the valves seal up just fine. The rocker posts have been donated to another engine and I'd have to replace them with other posts (I have other posts, but the ones in this head were chosen for a few reasons), as well as remove a snapped off exhaust stud from the #1 exhaust stud position. This head is also very slightly out of true; I measured 0.004 thou of warp. Very, very little water jacket corrosion. Other than the slight warp, and the busted stud, the head appears to be a good canadate, there is very, very little core shift that I can find.

 

I am planning to remove all the threaded in core plugs in the head, remove the valve guides, and strip the head completely to a bare, machined casting, and work through the preparation of a competition-grade cylinder head, best I can figure. I am not sure I want to yank the valve seats at this point in time, although they will be changed to fit larger valves, if it appears that larger valves will help with port flow. Since this head has the steel exhaust port liners, I do not think I will achieve proper competition grade performance, but finding an E30, Y70, or 05L head casting is only a continent away. (Honestly, I think the Y70 cylinder head is the best starting point for a head that wouldn't be allowed to be welded.)

 

I am also seriously considering leaving the head alone, refitting the rocker posts, and trading it straight across for an N42 head to do the exact same process to.

 

Yeah, the Y70 would be a good head to start with. It depends on what you'd rather; round exhaust ports in the Y70 or square ports like those found on the E30 and O5L heads.

 

I have the Y70 (two in fact) and the O5L head in my shed. I'm about to run one of my 26's with the Y70 head, stock size ports and valves for maximum gas velocity through the head. Valve shrouding is vastly reduced since this head was designed to fit to a block with bores only 78mm in diameter. The 26 it's on is bored 100 thou, now you know what I'm saying here!

 

I concentrated work on the valve seat area and bowl which, I believe, is where significant gains are to be had. I wasn't put off by the liners in the exhaust ports, I've run heads before with them in and never felt like the engine was restricted by them. In fact, the engines with them in always sounded louder (and meaner) than the square ported heads. What does that mean? Dunno.

 

The O5L has dinky little runners at 28mm's, smaller than the other two heads (30mm's). Certainly, this head would be a very interesting base for a 'sik' head buildup. If you ever want either head, Pm me and we can talk. (Need a P65 intake, got that too, LOL)

 

Cheers.

[Oddmanout84]

Mn47 and n47 heads aren't the same...but that's a heckuva nice polish in that chamber!

 

 

You know, I suspected as much, but I don't see that many "regular" Z N47 vs. MN47 pictures around. Still debating on whether to remove the exhaust liners or not. I'm not sure if this head is even worth the work I'm putting into it, but it's essentially practice for the future. I don't see it as a total waste in that respect. With any luck it'll work "decently" for my current NA budget build.

Edited July 25, 2012 by Oddmanout84

[roger280zx]

You know, I suspected as much, but I don't see that many "regular" Z N47 vs. MN47 pictures around. Still debating on whether to remove the exhaust liners or not. I'm not sure if this head is even worth the work I'm putting into it, but it's essentially practice for the future. I don't see it as a total waste in that respect. With any luck it'll work "decently" for my current NA budget build.

 

No picture comparison needed. The open chamber is a dead give away that it is a Z head. Small, peanut shaped chambers indicate its a Maxima.

[Noddle]

No picture comparison needed. The open chamber is a dead give away that it is a Z head. Small, peanut shaped chambers indicate its a Maxima.

They were standard for other, non US markets,

the MR30 Skyline has them, I have 2.. (mn47 heads)

Edited July 26, 2012 by Noddle

[Xnke]

Going to have to put this on hold a few days, gentlemen. Just had a P90 dropped in my lap that needs to be gone through and cleaned up, so that'll consume a lot of my time for the next little bit.

[Perfect240z]

You know, I suspected as much, but I don't see that many "regular" Z N47 vs. MN47 pictures around. Still debating on whether to remove the exhaust liners or not. I'm not sure if this head is even worth the work I'm putting into it, but it's essentially practice for the future. I don't see it as a total waste in that respect. With any luck it'll work "decently" for my current NA budget build.

 

 

I think theres some info on about removing the liners don't improve anything for the head. I would leave them, I have a MN47 thats in pretty good condition sitting in my attic.

[Oddmanout84]

I think theres some info on about removing the liners don't improve anything for the head. I would leave them, I have a MN47 thats in pretty good condition sitting in my attic.

 

Yes, on a mostly street build it's probably not worth the effort. I've just been toying with the idea of removing them because I'm getting my first practice with this head. Wouldn't mind getting myself an MN47, N42, P79 etc later down the road for other builds, especially if I can do a high compression build like MonZter did on his L24.

[Mack]

The MN47 is pretty sweet. I was/am running one on an L28 with flat tops and a felpro head gasket. The compression ends up being somewhere around 11.7:1. which is about the limit for street gas. I am running megasquirt and some mild head porting with some bowl blending and a few other things. I did have to pull some timing, but with the high quench, it doesn't need all that extra timing anyway because it is less distance for the flame front to travel. My claim to fame was the one time I had the sucker dyno'd (while running stock injection and a very faulty E1280 that only let it run up to 4500rpm) and I was hitting around 140rwhp @ 4200rpm. Not too bad for an engine slapped together in the car.

 

I wouldn't bother with removing the liners. Unless you are going FULL race, it really won't make that much of a difference.

[19762802+2]

The MN47 is pretty sweet. I was/am running one on an L28 with flat tops and a felpro head gasket. The compression ends up being somewhere around 11.7:1. which is about the limit for street gas. I am running megasquirt and some mild head porting with some bowl blending and a few other things. I did have to pull some timing, but with the high quench, it doesn't need all that extra timing anyway because it is less distance for the flame front to travel. My claim to fame was the one time I had the sucker dyno'd (while running stock injection and a very faulty E1280 that only let it run up to 4500rpm) and I was hitting around 140rwhp @ 4200rpm. Not too bad for an engine slapped together in the car.

 

I wouldn't bother with removing the liners. Unless you are going FULL race, it really won't make that much of a difference.

 

Those are some decent numbers, did you have Headers and exhaust on the car? I was running a L28 from a 280zx with the P79 head some MSA 6-3-2 headers 2 inch exhaust and some 73 240z SU's on the E-46 manifold and I made 145hp 150ft/lbs at 5,000 rpm. I bet with some ITB's or a carb setup that would make some really nice power. I am also at 6200 feet above sea level as well.

Edited July 28, 2012 by 19762802+2

[Mack]

all it had done to it was a 2.5" mandrel bent where the cat is supposed to be back exhaust, a 60mm tb, cleaned up the bumps out of the ends of the intake runners, minor bowl blending on the head and gasket matching on the intake/exhaust manifolds and head and a 260Z "C" stamp camshaft.

 

future plans before an engine swap include a set of 40MM itbs and maybe a COP set-up and a delta re-grind pushing the limits of the stock springs as far as lift goes and a healthy bump in duration.

[Heroez]

Those are some decent numbers, did you have Headers and exhaust on the car? I was running a L28 from a 280zx with the P79 head some MSA 6-3-2 headers 2 inch exhaust and some 73 240z SU's on the E-46 manifold and I made 145hp 150ft/lbs at 5,000 rpm. I bet with some ITB's or a carb setup that would make some really nice power. I am also at 6200 feet above sea level as well.

With that output the stock exhaust manifold wouldnt be restricting and would reduce under the hood temperatures. The header will radiate heat much easier. The 632 header is the worst design I've ever seen. Low hanging, bad flowing junk. To give you a picture of their real value, I was given some for free, and I put them to their best use: A curiosity hanging on a wall. Something to look at once in a while and chuckle.

 

I have a mn47 too, so I like to see what people say. One day I will put it to use.

Edited July 29, 2012 by Heroez

[Xnke]

Project Ended. Just picked up a P90 head casting, so this head will go back on the shelf for now. I have a few Z car N47's coming from a few other sources, so there will be some roundport conversion experimentation going on with one of those, we'll see what it takes to get it to flow good. The 4-cylinder guys have been able to get some very nice results out of the roundport heads, after removing the liners, provided that the port floor has a little sculpting done to it.