mn47 and n47 heads

i have both heads and they are both stamped n47. Mn47 is slang for the maxima one to z folks, and zn47 is slang for the z one for maxima folks. Look at the chamber on the bottom mating surface, if its shaped like a heart its the mn47. if its round, its the zn47. Mn47 on flat tops na l28 will get you about 10:1 comp. Just have the big 280 valves installed and power up!

A Z N47 (~44.6cc chambers) on a flat-top bottom-end L28 will get you ~9.8:1.
Maxima N47 (~39.5cc chambers) would put you ~10.8:1.

when i plugged in the numbers i got 10:1 on a stock head gasket. Atlantic z club has the link to the calculator

Thanks all, After searching here and over at classicz i found that the stamping is the same. Everything I have read leans to the 10.8:1 comp which is too high for me. I'm going to be putting a P90a on it. SoI now have a reworked mn47 for sale.

heroe said:

when i plugged in the numbers i got 10:1 on a stock head gasket. Atlantic z club has the link to the calculator

Click to expand...

Funny, should be a lot higher. A 44.6cc N42 or N47 on a flat-top bottom end gives 9.8:1 CR. A ~39.5cc Maxima N47 will give significantly higher CR than that. I'm getting 10.8:1.
What are you using for chamber volume? I don't have a definitive number, a couple of sources give 39, a couple give 40, a couple that say between 39 and 40, so I went with 39.5cc.

Az240zz said:

Thanks all, After searching here and over at classicz i found that the stamping is the same. Everything I have read leans to the 10.8:1 comp which is too high for me. I'm going to be putting a P90a on it. SoI now have a reworked mn47 for sale.

Click to expand...

P90 will give you 8.5:1 CR. A better bet than 10.8:1, but definitely on the low side. A Z N42 or N47 would give you 9.8:1, which might be a bit on the high side for a stock cam, might have to retard timing. That said, I was able to run full advance with a stock-cam N42 at ~10.25:1 on my 3.1, so ymmv...

I went with the P90a because its what I got. I also have an E31 available and can get a N42. I am a low tech guy.

you can lower the mn47 compression some by using a thicker head gasket. Maxima head, 2mm gasket, stage 1 cam. Sweet.