Hi guys,

We are rebuilding a 280z engine and the head seems to be replaced. The engine block says 6831M and N42.

My mechanic says it needs a N47 head. Does it need N42 which matches with engine block or N47?

Thanks.

Edited April 19, 20205 yr by MH77280Z

I did some more research seems like N47 is the right head. N42 seems like the engine block number. Also how do you verify if this is matching engine with the chassis or trans?

There are blocks with E30, E31, P30, N42, F54 casting numbers

There are heads with E30, E31, E88 (early and Late) N42, N47, P90, P90A. I think the N47 was on a Maxima ICBW

Some of those matched head to block but those are just casting numbers. 

The serial number under the back cylinder matches the inner fender well plate for the 240, 260.

For the 280 Nissan dropped the engine number on the plate but it is still on the block. 

As far as I know there were no matching transmission numbers. There are certain ones that were in a date range of cars. The A and the B style (two different ones), and a C in the turbo. 

I hope that helps some, I am no numbers expert so others may chime in with more data. 

 

 

Only the engine block can be matched to the chassis and that is only up to 1976 (maybe 1977),  Nissan put the engine block serial number on the ID plate by the brake master cylinder.

Either the N42 or N47 head will work exactly the same on the N42 engine block.  But the exhaust manifold for an N47 head does not work well with an N42 head.  So that's really what you need to match, the exhaust manifold. If you have an N42 head with a square port exhaust manifold it will bolt right on to the block and work fine.

Your mechanic should know this.

p.s. 1977 was the year that Nissan changed from the N42 head to the N47 head.  So you could have either.  Your mechanic might be looking at some sort of database and using 1977 as a guide.  But the N42 head is found on 77's also.  Just rebuild that N42 head and use it.

 

Edited April 19, 20205 yr by Zed Head

12 minutes ago, Zed Head said:

Only the engine block can be matched to the chassis and that is only up to 1976 (maybe 1977),  Nissan put the engine block serial number on the ID plate by the brake master cylinder.

Either the N42 or N47 head will work exactly the same on the N42 engine block.  But the exhaust manifold for an N47 head does not work well with an N42 head.  So that's really what you need to match, the exhaust manifold. If you have an N42 head with a square port exhaust manifold it will bolt right on to the block and work fine.

Your mechanic should know this.

p.s. 1977 was the year that Nissan changed from the N42 head to the N47 head.  So you could have either.  Your mechanic might be looking at some sort of database and using 1977 as a guide.  But the N42 head is found on 77's also.  Just rebuild that N42 head and use it.

The previous head had a crack. Seems like overheating. Engine block and rest of the stuff seems OK. Crack was very micro that couldnt hold pressure test. The mechanic told me it is an N47 head. So we are just going with N47. The engine and stuff have never been taken out all stock so I am sure it has the right manifold. I just got confused by the N42 on the engine block.

Thanks for the explanation.

 

Makes sense.  Nissan used the N47 head on the N42 block until they changed to the F54 block in about  mid-1980.

Nissan did do some odd things with the cam lubrication though in 1977.  They switched from the spray bars to the internally oiled cam.  Make sure that those parts are right.

Carry on.

My 9/76 built '77 has the early switch n47 head. Oiler cam and spray bar. I would put a turbo oil pump on if yours has both.