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N42 Vs N47


Nismo280zEd

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Ok so I was always under the impression that the N42 head compared to an N47 head was a higher would yield higher compression due to the smaller quench areas on the heads. Well my motor blew a ring about two weeks ago and I bought an old Z motor off a member here that went to V8. I'd been using it for parts and i thought it was and N47 motor and head. However, Now that i have my head on it and new gaskets, etc etc. I was outside scrubn' it down to paint the block, when the grease came off it read N42 not N47. I couldn't believe my eyes. So I ran over to the old head I pulled off it N42. So am I getting excited for no reason? I though this motor was a standard 77 280 motor. However the pistons looked different than mine too. They have notches cut out in each piston towards the front (timing cover) of the motor. No numbers on the pistons though.

 

So basically I'm asking the difference between N42 heads and blocks compared to N47 heads and blocks.

 

-Ed

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All 75-80 blocks will read N42 for a casting number.

 

 

75-EARLY 77 has a N42 head.

 

Early 77-80 has a N47 head

 

81-83 has P79, NA.

 

 

Those notches you are reffering to are the FRONT notch indicators. the Piston pin is NOT in the center of the piston, so they put those notches so you can put them with the offset the correct way.

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N42 head has the same cc's as the N47 the differances are...

 

N42 bronze valve seats (because of leaded gas) square exaust ports

 

N47 Steel valve seats (unleaded gas) round exaust ports with steel exaust liners. The liners are suspended hoops in the exaust path that heat up to burn off pollution.

 

 

You will get people fighting about which head flows better ... but most N/A people prefer the N42, but... you need to have the valve seats changed over to steel and you might as well replace the valve stem seals and get a 3 or 5 angle valve job while your at it.

 

Good luck with your engine build.

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hmm for some reason i thought the N42 head yielded a higher compression. What's the casting number on the old maxima heads? That's the head I was thinking of I guess.

 

Yeah I finished building my back up motor last night, it'll go in the car sometime this weekend. When I'm not workn' on the two broken maximas, and doing a brake job on a pontiac. As for my motor build up I want to rebuild it a little stronger with out getting into custom parts. I had some sort of ring failure on the #5.

It didn't completley fail cause theres no scaring or scratching in the wall, or carbon trail or anything. It looks identicaly to all the others on the top as well as the cylinder wall. I think it might be something minor with the ring. At anyrate i won't know for sure till i pull it all apart. Does anybody here run Moly rings? the harder rings? I just want a really reliable motor. In the next coming years i'm gonna have to start drivn' it around 80-90 miles each day for my University Degree. I need to have it rock solid for then.

Thanx for the help

 

-Ed

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the maxima head has the casting number N47 even though many people on here call it the MN47. the chamber design it much like the P79/P90 heads and if I remember reading it correctly, its a little taller than the normal L6 heads.

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Ok guys,

 

This in regards to cylinder heads…

The Z car N-42 and Z car N-47 heads share the exact same combustion chamber shape and volume. N-42 was available in ’75 and ’76, the N-47 from ’77-’80, for the domestic market. The ’76 N-42 heads did receive the steel intake seats as did all L-series heads from that time on, where as the ’75 N-42 heads had those soft bronze intake seats, unless they have been replaced in the past. The port differences themselves has already been covered so I wont rehash that.

Now as for the Maxima N-47, it has the same ports as the Z car N-47, but the chamber is completely different than any of the other L-series head and is the smallest of the L-6 combustion chambers in volume. The Maxima N-47 also uses a smaller intake valve.

If any of you want some “real good” detailed info regarding any of these heads and which heads work and don’t work on the various short blocks, I strongly recommend reading these threads… Both of these threads are VERY VERY informative in regards to the details of the L-6 cylinder heads….

 

http://forums.hybridz.org/showthread.php?t=104420

 

 

http://forums.hybridz.org/showthread.php?t=105653

 

 

If I get the time, I should just take pics of the chambers and ports of all the L-series 6 cylinder heads that Nissan manufactured for the domestic market as we have at least one copy of all of them, E-31, E-88, N-42, N-47, P-79, P-90, P-90-A, and the Maxima N-47.

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well said Paul!

 

Were do you live Paul?

 

 

I live in Sandy Oregon, just east of Portland. We live pretty much right in between Portland and Mt. Hood.

 

Where about in Cali do you reside?

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im in southern Californina, Covina. I live in a dumpy part of town... oh well.

I've been looking for a Z buddy in my area... no such luck... I hear its beautiful in OR. Thanks for all of your Z help over the years. I've been bugging you for a while and you've always been helpful.

 

Thanks

 

Sincerely, Matt-

 

P.S. sorry for hi-jacking the thread

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