N42 head questions

[siteunseen]

I went by a local machine shop last week to ask if they would consider re-working my N47 head off my '77. He had a head that was, as told by the customer off a '80 ZX, not picked up from 2006. He got it down and removed the bag it was wrapped in and to my surprise it was a N42 with a oiler cam and the cam towers did not have the holes for a spray bar. It has the hole up front for a mechanical fuel pump but no plate covering it. So could it be that someone had new cam towers installed and the power steering pump on the '80 car covered the fuel pump opening? All my searching shows the P79 had that same hole but would the head still be stamped N42 or P79? All I see is the N42, no other stampings. And would $250 be a good deal for this? It's ready to bolt on and looks like new they have $275 worth of parts on it. I'll have to get a plate made for the fuel pump hole and MSA said they would exchange the round exhaust port header I just bought for the square port so it seems to be a no brainer and that's what scares me. Advice?

[siteunseen]

I got my P's mixed up. It's the P90 that had the fuel pump hole at the timing chain but it has round exhaust holes with liners so I know this is a N42. It's the cam towers with no holes for a oil bar that I don't understand.

[Zed Head]

Not sure where the power steering pump comes in to play. That would be an odd way to seal a hole in the head. You said that it has N42 cast in to the side right, so really no reason to ponder the P79 option. It would be strange if a 1980 car came with an N42 head, although I've read that markets outside the US took longer to change.

I think the old-timey phrase to describe what you're looking at is "a pig in a poke." If the cam towers have been replaced, then it's obviously not all stock parts. Does it have the stock cam or an aftermarket cam? Maybe someone installed an aftermarket cam, with the oil passage, and changed cam towers to fit.

If it has an aftermarket cam, then your EFI system might have tuning problems, from what I've read. Even if it has the P79 cam, it might have problems, since they have a different grind, although I haven't seen an example of someone trying to run a later ZX engine on an early EFI ECU and AFM, so can't really say.

Sounds interesting though, if you can get more information about what it is.

[Travel'n Man]

After a head has sat for so long I would really have to worry about any damage to the valves - if not handled correctly (and who knows how many people handled it) you could have some hidden damage. I'm assuming the intake and exhaust valves are in the head.

You stated it was wrapped up in a bag - it really should have been protected in a box.

[Zed Head]

It's possible that someone with an 80 ZX was going to put an N42 head on their F54 flat-top block, to get a higher CR (about 9.8). It's a fairly popular modification. That might fit the "N42 head on 1980 car" scenario. If that was the case, it wouldn't be surprising if they had a different cam installed, to lower cylinder pressures and avoid detonation, or just to make more power.

If so, you'll still be on the edge with your stock EFI control system.

[siteunseen]

I just went by and looked at the head again. The cam it has is new and stamped E30 just like the one on my N47 and is a oiler cam (small hole in the lobes) the machinest said that the cam towers were new also according to the bill they have on file. And they put 2 new stock valves in and ground all of them to the right height, I have know idea what that means. It is wrapped in heavy plastic bag with 2 pieces of cardboard for the bottom, attached with zip ties. And, get this, "if it doesn't work I'll buy it back" warranty. Should I take the chance? I've read alot of people run the N42 just for the square exhaust and no liners. It is supposed to be close to the E88 I think from the 240's which are hard to find because of the low number produced. I'm worried my N47 will be costly to refresh because of broken intake bolts that where fixed with some kind of putty, maybe JB Weld, and the PO drove the car and said it had an exhaust leak. When I got the intakes off the gasket was in many pieces and the exhaust manifold had some odd colored holes. #1 & 2 are soot covered black, #3 & 4 are white in the middle and soot covered along the outer edge, #5 & 6 where the bolt was broken and leaked really bad are pure white. Sorry for the rambling but I'm trying to describe as best I can because I didn't carry a camera to the machine shop and I'm kind of anxious because my 30 day return for the header is the 8th of October. One more thing, the drivers side of the block is covered with oil, greasy and grimmie ecspeacily under the thermostat housing. Passenger side looks fairly nice to be 36 years old. If you can make sense of what I've written would you buy this pig in a poke?

[siteunseen]

I went back and he let me bring it home to compare to my N47.

Edited October 4, 2011 by siteunseen

[Zed Head]

With the warranty (if you trust your mechanic) and the information, it looks like it's worth a try. Did you get an estimate on rebuilding your N47 for comparison? Since you won't be buying new cam towers, or maybe even a new cam, it might be cheaper for a refresh. The new head won't really be any improvement over a rebuilt N47. But if your head is warped or needs machine work, who knows.

The N42, from what I've read, will be essentially the same as your N47. The only significant change was the liners in the exhaust ports, for emissions purposes, and, apparently, they flow about the same. Lots of good information on the Hybridz site.

I believe that matching the valve heights is so that the same thickness lash pads can be used on all valves. Is the cam installed? If so, you should find out if the "wipe pattern" has been verified as correct. Also, with a new cam, you should read up on break-in procedures. Apparently, an additive that used to be common in motor oil, ZDDP, is not there any more and new cams have been self-destructing as a result (a hot topic but most are being safe rather than sorry). Search ZDDP or ZDP and "cam" on Google.

Maybe someone who knows the cost of rebuilding a head can chime in. $250 for a drop on replacement seems like it might be a good deal.

Edit - Just saw your pictures. That cam looks used, didn't realize that. Changes things somewhat. Since you have the head in hand, maybe you could find someone in the area who knows Datsuns for a second opinion. Good luck.

2nd edit - I don't know what a "new" Nissan cam looks like. Maybe new Nissan looks used? Maybe it's just the picture. Also, you should confirm that the the other valve seats were ground. It might be that someone just had two valves replaced on an old head, and you're just looking at buying another used head. It should work fine, it's a question of value now.

Also, from what I've read on Hybridz, the square port headers and manifolds will work fine on round port heads, but not vice-versa.

Edited October 4, 2011 by Zed Head

[siteunseen]

Well I'm going to be vice-versa. I bought a round exhaust port header for my '77 and would have to send it back, $30, to MSA, then they will charge me another $30 to ship '75 & '76 square exhaust port header to my house. Unless they can polish a cam or something, up close in real eye time, the cam looks to be new. It has white grease all over the lobes and he did say I would need to pour oil over the cam because it has been sitting so long. So if I send my round header back and get square then I could use either N42, square, or my original N47, round? $300 for a better flow exhaust head that's ready to bolt on. I won't sleep very well tonight.

[siteunseen]

I've already carried it back but looking at those pictures it does look suspect to use. He said it was a new stock cam though and he seems to be very honest. I need to see the bill he has for parts and labor. The $250 price is for the parts and I'm sure some labor for the valve grinding.

[siteunseen]

Thank you Zed Head for info I overlooked. Didn't know square headers will work as well on diamond or round exhaust. I'm sending my round headers back to MSA for squares and buying the N42 head locally. Maybe it would work long enough to rebuild original N47. I cut yards in the grass season so " easy come easy go" is my way to finance this project for another month or so theen it's March 2012.