Jump to content
Welcome Guest! Please read more information about our club!

Issues swapping E88 head with N47 head? (L24 bottom)

Tomzern
Tomzern
in Engine & Drivetrain

Featured Replies


comment_469449

Thanks for those pictures Tomzern and site.  Those are the first I've actually seen, and they do look like the way a factory would do it, crude but effective.

 

My thorough side though, sees that one block is from Europe and the other from SE Asia.  Tasmania. Australia.  I wonder if the US models are the same.  Curious enough to get me to remove a head some day if I ever find a Maxima in the wrecking yards.

 

Those who think the Maxima head is of high value should read up on "quench".  It's not a major power booster, and some people think that Nissan didn't get it quite right.  The bigger valve is worth something for sure.  The cam profile would be worth knowing too.  I'm not sure the true added-value matches the mystique though.  And there are some odd theories proposed out there about how smaller valves increase performance due to air flow velocity increase. 

 

Anyway, a person can't go wrong saving these old L engine parts either way.

  • Author
comment_469471

Sooo, back on topic; It's now a fact that I have to make those relieves in my block to get the MN47 head to fit, BUT do I need a different headgasket with relieves as well, or can I use the normal L24 headgasket I already have?

 

 

I originally thought that I had a conventional N47 head, but now that I know I have the "famous" MN47 head another question comes to mind; Should I use the MN47 head instead of an N42 head (which I also have) for my L31 stroker build? The MN47 has better "quench design", but the N42 does not have the exhaust liners which makes it possible to do some improvements to the exhaust ports as well. hmmmm

 

 

Appreciate all the help :)

 

 

-Tomzern

comment_469648

So I posted a question on a Maxima site and a guy replied that yes, his block is notched, but on the exhaust side only.  Didn't know that.  Which is even odder since that's the small valve, even though it is bigger than the 204Z L24 valve.  Makes me wonder if Nissan didn't do it to solve a shrouding problem.  The exhaust valve is the hot valve and would be sensitive to uneven cooling.  The side of the valve head closest to the cylinder wall would be cooler due to low exhaust gas flow by it, and radiative cooling.  Emissions engines (1980's and on) tend to run hotter.  Maybe Nissan had a valve warping problem.  Just a guess.  I can't really figure out what the notch is for.

 

So it may be that the MN47 will drop right on to an L24 or L26 with no notching, but there are durability reasons to notch.  Avoiding warped valves maybe.

comment_469650

I have photos of a L26 blocked that notched only for the exhaust. Its a european engine.

That makes sense because the inlets were still the same (42mm) size as the L24. In the L26 theg enlarged the exhaust valve.

Ill try to post them later. They are on a backup drive.

Chas

Edited by EuroDat

comment_469657

Here's a video from a guy that sounds States-side, clearly showing a notch in the #6 cylinder, exhaust side.  0:17 in.  I've been reading about notches for years but it seems like there was always a question about where they came from, and no pictures.

 

 

Still wonder what the reason is for them.  Maybe just insurance during assembly, or maybe they do touch if you get a bad mix of tolerances.

 

Edit - actually I think that olderthanme may be a member here.  I know that he's on Hybridz, or was.

 

Edit 2 - he is but last posted in 2008 - http://www.classiczcars.com/user/10107-olderthanme/

Edited by Zed Head

Create an account or sign in to comment

Go to topic listing

Important Information

By using this site, you agree to our Privacy Policy and Guidelines. We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.