Here's an interesting thread - http://forums.hybridz.org/topic/62691-l6-heads-pics-and-descriptions/

Here's a side-by-side of the MN47 from that Hybridz link and my N42, which has the same "open" chamber shape as the L28 N47.  You can see the "quench' area on the MN47.

 

 

Here's another informative thread with all the pictures you need, I think. 

 

http://forums.hybridz.org/topic/96188-my-200-l28-surprise/

That's interesting.  I've never seen that mentioned for the factory stock Maxima L24E.  I may have missed it though.

 

I didn't think that Nissan did any valve relief on their blocks.  There's rumor about the 260Z but many people think the "reliefs" are actually from the valves nicking the bore edge.  

 

From a manufacturing perspective, it's a lot of work for not much benefit.  Best to just design the head so that it works right, and the Maxima head was only used on the L24E.  I can't imagine being the engineer that has to explain that every block needs extra machining because the valves will hit otherwise.  Just doesn't make sense.

 

It's a bit more realistic that the relieves are there from factory, than that they have been nicked out by the valves over time. I will post pictures of the relieves on my L24E block tomorrow. They definitely look machined.

 

Another thing. My L24E comes from a laurel that was produced from 1984 to 1989. The maxima L24E was used from 1981 to 1984, so there may be a few differences on those two engines as well.

It's a bit more realistic that the relieves are there from factory, than that they have been nicked out by the valves over time. 

Have to disagree.  The nicks seen could be from worn valve guides with a close tolerance.  Machining the block is actual money spent by the company that could be avoided.  Potential money savings in high production automotive factories is one of the most powerful force you'll ever find.  Pennies matter.

I don't doubt that, and I am no engine machinist or engineer, but the way those relieves look tells me that they are not knocked out by the valves. Especially since they are looking exactly the same on all 6 cylinders.

The question remains though as to what you have.  You might have an L28 N47 head on an L24 block, that somebody notched to make it work.  There's a whole other recent thread on this forum about that.  It's fairly common, to get the bigger valves.

 

We'll know more when you figure out what head you have.

My guess (and hope) is that I have a newer european version of the US "MN47" head (ref 84-89 build year for the Laurel L24e)

 

I'll be back with pictures tomorrow! 2:17AM here now, so might consider calling it a day

 

 

Oh, and thanks for all your help so far! 

Edited May 9, 20159 yr by Tomzern

Zed,

Not sure that Nissan  would be the only ones that actually relieved bores on factory engines -at least from my research.

 

You could be careful and notch the bore without dismantling the engine. Shaving cream and a drum sander would make quick work of it. A 2" drum sander with 80 grit and a couple of hours of prep and done. 

I'm basically playing devil's advocate I guess.  I would like to see an actual factory block with factory-notched bores.  I just haven't seen it in all of the 5+ years I've been on the forums, and all of the old posts I've read from way back in that time.  I get that an L28 head on an L24 bore would need it.  Can't see that a Maxima L24E head on a Maxima L24 block would.  

 

The valves are the same size as 260Z valves (looked them all up on OReilly auto Parts).  Only the exhaust valve, the smaller valve, is bigger in the Maxima head than in L24 heads.  So, it's not a valve size thing, it would have to be a combustion chamber shape and valve seat placement issue.  But I think that is determined by the cam, and rocker arms, which are the same.

 

My logic center just can't find a reason that the Maxima N47 head isn't a straight bolt-on, and there doesn't seem to be any evidence, despite all of those Maxima engines out there.  Maybe Tomzern has the first one.

 

Considering the bigger valve (one) and the slight bump in CR, it's surprising that more people haven't just swapped the complete L24E engine in to their 240Z's. Looks like it has the carb manifold mounting holes.

 

Anyway, let's see how this plays out.  Tomzern, where's your camera?

I was talking to my Dad last night and he said they used to run the piston down 2 or 3 inches then pack the rest of the cylinder with axle grease before tapping out broken head bolts.  Same as shaving cream.

 

Here's some good pictures of a factory notch from a Skyline.  Post #22 http://forums.hybridz.org/topic/70734-notchingbevelingbutterfly-l24-block-for-valve-clearance/page-2

 

 

Here's where Blue used an MN47 on an L24, post #2 http://www.classiczcars.com/topic/50973-24-valve-reliefs/

Edited May 9, 20159 yr by siteunseen

Click on this and you'll see.

 

Edited May 9, 20159 yr by siteunseen