Friday, November 5, 2010


As most of you know I recently picked up an L28E to swap into my 73 240z.

I got it on Craigslist for $200 with all the EFI gear and a 4 speed transmission.

The motor came out of a 1975 280z so it shipped with the N42/N42 block/head combo. The guy mentioned that he thought the previous owner might have replaced the head on it at some point because it was considerably cleaner than the rest of the motor. After checking the stamp I noticed it was an N47.

After finally reading through all of the posts in the L6 heads thread (That I had previously skimmed).

I noticed something funny about my N47.

From Z

From Z

It has Quench pads, and MUCH smaller combustion chamber than the standard N47. 38.5cc vs the Z car head volume of 44.6. Smaller combustion chamber = higher compression!

This is a standard N47 that was originally released for Z cars:

From Dirty S30

Notice how the entire combustion chamber is recessed.

Did I happen to score an MN47 by accident? The MN47 head was stamped as N47 but shipped on Nissan Maximas between 1981 and 1984.

If this really is an MN47 head, with the previous owner's configuration of stock N42 dished pistons, rods, crank, and the 1mm Felpro head gasket this little guy was seeing a 9.2:1 compression ratio in the MN47's 38.5cc chamber!

That's a touch better than the 8.26:1 that it would have had the the Z car N47 and a stock Nissan gasket!

I am still researching this and will keep you up to date with what I find out. Previously I knew nothing at all about this head.


  1. This comment has been removed by the author.

  2. Sweet deal!

    Its an awesome head because you have a high quench design like the earlier heads i.e E31 & E88 (like you said), a more efficiently designed combustion chamber than the earlier heads, AND you get the larger valves found on L28 series heads.

    Awesome reasearch & good score dude!

  3. I know this is old and you probably know by now. The MN47 has as temp sensor in between 5 & 6 spark plug holes. The n47 and earlier did not have that.