1978 280Z 2+2 Cylinder Head Removal

[MillerTime802]

@ Captain: you are correct. Thanks, Brad.

[EuroDat]

I know where captain is going with his question. The P79 came on the F54 block with flat top pistons. Your engine is a N42 with dished pistons. The dish form is about 10.9cc. The chambers on the heads for the N47 44.6cc and the P79is 53.5cc.

Putting this head on your block will lower the compression from 8.3:1 down to 7.8:1.

You need a N47 or a N42 with exhaust manifold and preferably with cam because the N42 uses an externally oiled cam. Your N47 uses a internally oiled cam through drillings in the cam.

There are plenty of N47 heads around. Most performance buffs wont touch them, but for normal street use they do the job just fine. Remember to check for cracking around the valve seats among other things like warping and shaved head gasket surface.

Chas

[MillerTime802]

@ Euro: Thanks for the info and the time you've invested sharing your knowledge. I'm starting to learn a bit about the head and block, so if you don't mind, I'd like to make sure I understand what your saying:

1. I totally understand the lower compression and the reason for it. In your opinion, do you think this is significant for a a daily driver.

2. The N47 head is the stock head for the N42 engine block. You mention I can use an originally coded head (N47), for obvious reasons. Or, an N42 head? Are you saying there is an N42 head to use with the N42 engine block? And get one (N42 head) with a cam because of the oiling difference, corrrect?

3. Assuming question #2 is yes (there is an N42 head), then as long as the head and cam match, there isn't a problem in changing from the stock (N47) internally oiled cam; to the other (N42 head) which is "externally" oiled cam. Correct? You also mention the exhaust manifold. Will the stock exhaust manifold (for the stock N47 head) fit on the suggested N42 head?

4. Another subject, same genre: Do you know if the P79 head that my daughter purchased (which has the cam on it) uses an internally or externally oiled cam?

5. Lastly, I understand the P79 head is used on 1981 - 1983 ZX cars. I've also read in some other postings that the P79 is often used on the P42 block because of its durability and good design. Apparently the head is milled to make up the difference in compression ratios, and the cam towers are shimmed to take up the chain slop created by milling..................You sound very knowledgeable on Z engines, so do you think this is accurate?

Thank you, and others, for your time. Soon, I'll know more that I need to know

Brad

Edited April 15, 2013 by MillerTime802

[LeonV]

I agree with Chas, an N47 shouldn't be too hard to find and will be cheap. The P79 will drop compression too much, but is otherwise interchangeable.

[MillerTime802]

@ Euro and Leon:

Question #2 and #3 above: I've learned there "IS" a head code N42 for the N42 block........so please excuse this revision to the question.

However, still wondering about the exhaust manifold question.

Thanks,

Brad

[LeonV]

E31, E88, N42, P90 have square exhaust ports.

N47, P79 have round exhaust ports (liners).

Thus, exhaust manifolds interchange between the N47 and P79, but not the rest.

Again, buy an N47 head. It's the cheapest and easiest route.

[SteveJ]

Brad,

This page should have some answers for you, too. Datsun L-series cylinder head timeline

[EuroDat]

Lets see, your asking quiet a bit of info. Ill try and sum up the main differences in the questions:

1: The lower compression will make a difference in power and you will notice. Like Leon says, that doesnt mean it wont work, just not perform like it could.

2: the 280Z came out with a L28 engine with block code N42 and the head code N42.

N42 Head:

Silicon/bronze valve seats.

An "external" spray bar to lubricate the cam.

Square shaped exhaust ports.

About August 1977 they changed the head to the N47 to comply with tougher emmisions in California.

The main changes are:

Steel valve seats to be able to use unleaded fuel.

Emmision chambers.

An internally lubricated cam. Drillings through the cam allow oil via the bearing journals to the cam lobes.

Round "diamond" shaped exhaust ports with a steel liner to increase heat for better emmision control.

There is also a maxima N47 head which is different. It has smaller closed chambers and can be identified by an extra sensor port between spark plugs 5 and 6.

3: If you choose to go for a N42 head you will need the exhaust manifold with square ports. Your cam will work on the N42 head, but its not advisable to mix match parts in the valve train. If you do you need to check lash pad paterns etc.

4: all heads after the N47 come with internal oiled cams.

5: The common mod for P90 (en P79) heads on earlier blocks it to shave 2mm of the head, raise the cam towers 2 mm to correct the vavle timing and fit the valves from a N42 or N47 head (there stems are 2mm longer). This raises the compression and gives you a good chamber design for better performance. Its a lot of work and for a standard engine not worth the effort.

Since you are thinking of using this head the way it is, my advice would be to trade it for a N47 head and go from there. The trade should not cost you much if anything since the P79 is more sellable then the N47.

Chas

[MillerTime802]

You guys are awesome! Thank you so much for the time and effort you've expending assisting me.

I'm getting your subliminal messages....get a replacement N47 head, ha. I'm going to start looking for one.

Anyone want to buy a 280 Z......I don't want to be my daughters mechanic for the life of this car, hahaha. Although she realizes now you don't buy 30 + year old cars and not expect to work on them. She'll be selling this one pretty soon, she can't afford to have a vintage car.

I'll post updates along the way.

Edited April 15, 2013 by MillerTime802

[240260280z]

N47 or N42 head will work.

[EuroDat]

Anyone want to buy a 280 Z......I don't want to be my daughters mechanic for the life of this car, hahaha. Although she realizes now you don't buy 30 + year old cars and not expect to work on them. She'll be selling this one pretty soon, she can't afford to have a vintage car.

That would be a shame if she looses interest after this is solved. They are an easy car to work and play with. This forum is always been helpfull for those in need and I have found many answers by searching the forum.

Good luck with the repairs.

Chas

[LeonV]

They're very simple to work on, but definitely not a good car to have for the mechanically dis-interested.