ussbhr Posted September 22, 2006 Share Posted September 22, 2006 my friend has stage 3 newly rebuilt n42 head sitting in his house since he total his 260z he wants me to buy for 200 however i have a l28et do u guys think i will get more power out of the head? can i even use the turbo manifold on the n42 ? Quote Link to comment Share on other sites More sharing options...
nismofiend Posted September 22, 2006 Share Posted September 22, 2006 Im not sure if this will help much but I took this from Zdriver. Looks like you might have exhaust leaks and poor boosting but, Im only going from the specs and not first hand experience. If it doesn't work your friend should sell the head to me CYLINDER HEAD Datsun used 3 1/2 different head casting for the 280zx. I'll explain the half part. I'll break it down by engine code: N42: N47 (79-80) diamond exhaust ports with liners F54: P79 (81-83 non turbo) round exhaust ports with liners F54: P90 (81-82 turbo) square exhaust ports, no liners F54: P90A (83 turbo) same as P90 but this head used hydraulic lifters. All are aluminum non-crossflow design. Valve Diameters: Intake:1.73" (44mm) Exhaust: 1.38" (35mm) Valve Length (N47): Intake: 4.53" (115.2mm) Exhaust: 4.57" (116.0mm) Valve Length (P79, P90/A): Intake: 4.45" (113.1mm) Exhaust: 4.48" (113.9mm) Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted September 22, 2006 Share Posted September 22, 2006 The N47 head on the 280zx was never used in a turbo application. I thought about using the N42 head for a turbo application (because I allready have one on my N/A engine) but I decided against it because that head is prone to detonation at higher compression raitios. The P79 would work for a turbo really well and of course the P90 works great. I know there are some guys that have used the N42 in a turbo motor and but they kept there motor will a lower CR. If you decide to go with the N42 head take lots of pictures and write it all down then share the info with the rest of us. Matt Quote Link to comment Share on other sites More sharing options...
Kennysgreen280zt Posted September 22, 2006 Share Posted September 22, 2006 N42 is a square port just like a P90. Your compression will be bumped up to 8.5:1 or so. If youve got some extra cash, while swapping the head, get the 2mm metal headgasket and ARP studs. The 2mm gasket will drop the compression back down a bit. HTH Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 22, 2006 Share Posted September 22, 2006 I've got an N42 from a 77 right here, and it has round exhaust ports, no liners. Quote Link to comment Share on other sites More sharing options...
kj280z Posted September 22, 2006 Share Posted September 22, 2006 A 77 did not have a N42 it only came on 75 and 76 Z's... Check again it's probably a P79 Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 22, 2006 Share Posted September 22, 2006 As a matter of fact, the P79 came on the later models, I took one off a 78, and that's what is actually on the car. P79 has the liners in it, I've got that right here too. *edit* I just looked again, and N42 is clearly stamped on the head, and it definitely has round ports with no liners. This was the head that came in my 1977 280z automatic, but I have no garauntee that it is the original engine (in fact, I was told it was a reman, but I have no proof of that either) since I'm not the original owner. Quote Link to comment Share on other sites More sharing options...
zeiss150 Posted September 22, 2006 Share Posted September 22, 2006 wow ... I've never heard of an N42 with round exaust ports... I know the N47 had round exaust ports with steel liners in them the N42 does have round intake ports ... maybe its some kind of weird Auzzy head? 8.5 to one is a great CR if you dont want to use supper high boost levels. The N/A engine that I built has flat top pistons wich makes the CR with the n42 close to 10:1 with the 2mm HKS gasket (wich I have on my engine now) it lowers it to 9.2:1... just a little to high for a turbo motor with that head design. If I use a P79 or P90 with my flat top setup then I get a nice 8.5:1 with stock Head gasket... so that's why I chose the P79 head. Like I said the N42 head can be used and has been used ... but is it the best head for turbo... probably not. Matt- Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 22, 2006 Share Posted September 22, 2006 Guess I'll be posting pics tomorrow...anybody want to buy it? Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted September 23, 2006 Administrators Share Posted September 23, 2006 Hmmm… Factory ’77 Z cars came with the N-47 head which has a round EXHAUST port WITH liners. As far as I am aware of, Nissan did not offer a round EXHAUST port L-6 head without the liners on production cars. Either you are looking at the intake ports of an N-42 head, (square EXHAUST ports), you just didn’t see the liner, (previous owner could of removed the liners, but not likely), or you have a VERY rare and exotic L-series cylinder head that requires you immediately remove that cylinder head, carefully package it up and ship it directly me here at Rusch Motorsports for further LONG TERM inspection, testing, and evaluation… If the latter, let me know I’ll give you our shipping address… Quote Link to comment Share on other sites More sharing options...
speeder Posted September 23, 2006 Share Posted September 23, 2006 I have an N42 head that was reworked by the engine rebuilder ATK to have round ports with no liners. This was done to make it fit the round port exhaust manifolds. Dunno how this head would stack up flow-wise with the N42 or N47... BTW, The N47 is the head that was standard on the 77/78 280Zs. I have heard of some very late 78s that had the P79 as original equipment. So many different heads have been swapped onto these old L motors that it cannot be assumed that what's on there now is the one it was made with! Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 23, 2006 Share Posted September 23, 2006 Well, I went and looked at it to be sure just now. The actual hole in the head is round. I have a P79 on the car, and it has liners, so I know what those look like. This head does NOT have those, at least not as they came in the P79. The carbon mark around the exhaust port is sort of hexagon shaped, I assumed this was an artifact of my crappy header, but may that makes it a square port? I assumed (possibly wrongly) that the port shape described the actual hole shape, but these holes are definitely round. I left my camera at home, but the head is off the car (and here at work with me), so I guess I'll have to bring it home and take some pictures. I'm off at 3pm Eastern Standard time, for anyone that is anxiously awaiting these pics, so I'll be ably to post them sometime after that. *edit* I suspect it is something like what happened to Speeder's head. That would be in keeping with the previous owner's story that the owner prior to him had just put in a reman engine before the car died... Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 23, 2006 Share Posted September 23, 2006 Alright, I took some time to clean up one of the exhaust ports for its big photo shoot, and this is what I found: It looks like somebody welded it up, and then cut it out with a valve seat cutter or something similar. There is a lip about 1/4" deep all the way around, and looking down the port, you can see where it used to be square. I can't imagine what the point of this operation was, and it makes me glad I went to a P79. This lip seems very intrusive when you reach your finger in and touch it. I'll still post pictures later, just wanted to give an update. The outer holes are slightly larger than the intake ports, but they taper down for just over 1/8" at what looks like a 45 degree angle or so to the actual port diameter. Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 23, 2006 Share Posted September 23, 2006 I swear this is like trying to photograph bigfoot...my stupid digital camera wouldn't focus close enough for me to show inside the port, but here's what I got: and here is the combustion chamber, in case anybody is interested: Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted September 23, 2006 Administrators Share Posted September 23, 2006 Hmm.. That is a new to me… Definitely odd. If someone did weld it up and machine the port exits round like that, it seems like a lot of unnecessary work just to use a round port header/exhaust manifold. We have been using Round port headers on square port heads for over 15 years with no issues using Victor Reinz , (aka NAPA), square port manifold gaskets. Hmmm… It almost looks like it is factory… Maybe a JDM head of some ort? Anyone else ever see this before? Cylinder number 1 sure looks awfully clean… Blown head gasket/cracked head in chamber #1? That hexagon carbon imprint you mentioned is typical of the Felpro manifold gaskets as they are universal and will work on both round and square exhaust ports. Quote Link to comment Share on other sites More sharing options...
veritech-z Posted September 23, 2006 Share Posted September 23, 2006 Whatever it is, it's proffessional. I have a 35mm slr camera with a macro lens, I could try taking some better pictures with that and scanning them after I get the film developed if you think better pics would help in a proper diagnosis. *edit*cylinder one is clean because I cleaned it, along with exhaust port number one to clarify the pictures. Quote Link to comment Share on other sites More sharing options...
racerx260 Posted September 23, 2006 Share Posted September 23, 2006 I have a turbo block with an n42 head at 7 lbs of boost no intercooler.It runs better than the stock p90 head at 7.4 cr on 11 lbs of boost. much better low end than stock.I like it so much I'm building a second one just like it for my other car. Quote Link to comment Share on other sites More sharing options...
510six Posted September 23, 2006 Share Posted September 23, 2006 The combustion chambers look like an N33 head .Which is a JDM only head. Quote Link to comment Share on other sites More sharing options...
CantZme Posted September 23, 2006 Share Posted September 23, 2006 so what is compression with an f54 block (dished pistons) , stock head gasket with an N42 or N47 head? Trying to bump CR on my stock compression l28et. Trying to stay with stock dished pistons. 8.5cr would be nice but zeiss why do u say that the n42 is prone to detonation? Should i just deck the block and get a p90? i have a p90a head right now with hydraulic lifters, but as i have read these lifters are not good for higher hp applications and are prone to breaking. Quote Link to comment Share on other sites More sharing options...
racerx260 Posted September 23, 2006 Share Posted September 23, 2006 With a .4 over bore I have about 8.5 cr. If you use the p90 with dished pistons you will have the stock 7.4 cr. good for lots of boost but no tourqe below boost. the 8.5 cr will lower you max potiential boost level but greatly improve drivability at lower boost levels.Depends on what you want. Quote Link to comment Share on other sites More sharing options...
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