'75 280z - Head temp sensor question

[Neb]

N42 it is

42 minutes ago, EuroDat said:

I wonder what the PO did with the head, if he did anything too it. It's most likely bolted onto a N42 block. The head was designed for an L24 in the 1984 Maxima with the smaller valves and smaller chamber.

Chambers in the N47 are 44.6cc and in the MN47 they are 39cc. The N42 block also had dished (10.9cc) pistons. The F54 has flat tops and the P79 head had 53.6cc chambers.

The MN47 head on an F54 block would have a really high CR.

So if I understand this all correctly, that temp sensor + the N47 marking means the head is the (smaller chamber) Maxima head.. and would make this particular setup higher compression than the standard N47 head+N42 block?

[Zed Head]

Yes.  On an N42 block with the normal dished pistons it raises the CR to about where a ZX engine would be.  But with smaller valves, so not the same power level as a ZX engine.  People use them with flat top pistons to get an even higher CR.  Your engine is probably in fine shape, just not achieving its potential. 

Gasket height is 1.25, if you want to play around with a calculator.  Just pick any head and plug in 39 for volume.  Late pistons are flat-tops, early or turbo are dished.

http://www.ozdat.com/ozdatonline/enginedesign/

[siteunseen]

Does the exhaust leak around the manifold?

'75s have square ports on the exhaust manifold, that maxima head is round.

I'm almost positive the square will cover the round, hope so anyway, but the round will not cover the square? Could have that backwards though.

You can get the bigger intake valves and seats put in that head. No worrying about hitting the block but you'll have to grind some of the chamber around the intakes, unshrouding I think they call it. A good cylinder head rebuilder could work that head into something very nice and peppy. Probably needs to be refreshed anyway.

[Neb]

6 hours ago, siteunseen said:

Does the exhaust leak around the manifold?

'75s have square ports on the exhaust manifold, that maxima head is round.

I'm almost positive the square will cover the round, hope so anyway, but the round will not cover the square? Could have that backwards though.

You can get the bigger intake valves and seats put in that head. No worrying about hitting the block but you'll have to grind some of the chamber around the intakes, unshrouding I think they call it. A good cylinder head rebuilder could work that head into something very nice and peppy. Probably needs to be refreshed anyway.

No leaks around the exhaust manifold, so far as I can tell

20 hours ago, Zed Head said:

Yes.  On an N42 block with the normal dished pistons it raises the CR to about where a ZX engine would be.  But with smaller valves, so not the same power level as a ZX engine.  People use them with flat top pistons to get an even higher CR.  Your engine is probably in fine shape, just not achieving its potential. 

Gasket height is 1.25, if you want to play around with a calculator.  Just pick any head and plug in 39 for volume.  Late pistons are flat-tops, early or turbo are dished.

http://www.ozdat.com/ozdatonline/enginedesign/

That is a pretty fun tool.  So you're saying the smaller valves and higher CR kind of cancel each other out for performance benefits?  Now I wanna pull a plug and try to get eyes on one of the pistons.. who knows whats in there

Interestingly, I have another head.  It was supposedly rebuilt by a previous owner, not sure on where/when, but it does look like someone went through it.  Stamped E88, pictures below.  Would yall keep the N47 on there, or swap over for the E88?

[Zed Head]

People spend a lot of time, effort, and money to get the valves to stay open longer, via camshaft changes, for power increases.  Chevrolet's performance engines used to come with 2.02" intake valves, over the normal 1.94" valves.  That's like a 51 mm over a 49 mm valve.  The 2.02"s had problems with cracking between the seats but Chevy kept using them.  They mattered.  I only know that because I had a Chevy engine back in high school and 2.02s were a big deal.

You'll find all kinds of combinations and rationale for all of them.  The basics of creating power don't change though.  But, I actually backed off some of my power increasing efforts, via advancing timing, just to get back to nice solid dependable engine.  Messing around is a lot of fun though.

Measure the valves on your E88.  It's fairly common for people to put the L28 valves in those heads.  I think that one of them is already at L28 size.  The MN47 valve info is out there somewhere.

[Neb]

40 minutes ago, Zed Head said:

People spend a lot of time, effort, and money to get the valves to stay open longer, via camshaft changes, for power increases.  Chevrolet's performance engines used to come with 2.02" intake valves, over the normal 1.94" valves.  That's like a 51 mm over a 49 mm valve.  The 2.02"s had problems with cracking between the seats but Chevy kept using them.  They mattered.  I only know that because I had a Chevy engine back in high school and 2.02s were a big deal.

You'll find all kinds of combinations and rationale for all of them.  The basics of creating power don't change though.  But, I actually backed off some of my power increasing efforts, via advancing timing, just to get back to nice solid dependable engine.  Messing around is a lot of fun though.

Measure the valves on your E88.  It's fairly common for people to put the L28 valves in those heads.  I think that one of them is already at L28 size.  The MN47 valve info is out there somewhere.

1.74 on the intake valves, 1.375 on the exhaust

[siteunseen]

E88 is for carburetors and doesn't have the notch out for fuel injectors.

http://www.viczcar.com/forum/topic/12914-wtb-e88-efi-cylinder-head/

 

 

 

[Patcon]

The E88 also looks like it might have been cut. The casting numbers are pretty close to the edge. Some measurements would be in order there too. Also are the cam towers shimmed on that head?

[Zed Head]

2 hours ago, Neb said:

1.74 on the intake valves, 1.375 on the exhaust

Edit - apparently it is valve head diameter that you measure.  It's not what I would want to know but it's what is done, apparently.  So your valves are close to L28 size.  

 

Actually, it's hard to tell from the out edge measurements, which overlap the seat.  I think that the number is actually the seat diameter.  Where the flow happens.

1.74 and 1.375 are 44.196 and 34.925, so more likely 42 and 33, stock E88.  A guess.  Not large enough to be L28 though.  I could be wrong.  I forgot about the injector cutouts, so that's a consideration.  I'd just get what's in there running well, drive the crap out of it and see if needs more of anything.

 

Edited March 29, 2018 by Zed Head

[EuroDat]

The E88 onthe noth american L26 had 35mm exhaust valves. I think they increased the size for the tougher californian emmision laws. It also has different chambrs for better emmision, less power. It's often called the emision head when people talk about the E88 head. I think you have basically 3 types of E88 head, one virtually identical to the E31, the "normal" E88 and the E88 on the L26.

Going by your mwasurements, looks like someone already enlarged the inlet valve (1.73), thats if it was of a L26. If it is one of the early ones, they have enlarged both valves.

There is a thread here somewhere with photo's of the different E88 chambers. That could help you work out which head it was.

[Neb]

To think this all started with trying to figure out where my temp sensor hookup was, hah.  Thanks to everyone for all the input, this has been hugely educational for me. 

14 hours ago, Patcon said:

The E88 also looks like it might have been cut. The casting numbers are pretty close to the edge. Some measurements would be in order there too. Also are the cam towers shimmed on that head?

No shims on the towers on the E88 head.  Whats a good way to measure the head to see if it had been cut?  Or would the lack of shims make that not a possibility

 

16 hours ago, siteunseen said:

E88 is for carburetors and doesn't have the notch out for fuel injectors.

http://www.viczcar.com/forum/topic/12914-wtb-e88-efi-cylinder-head/

 

 

 

Is that something that could be machined in there?  Maybe farther down the road I'll have someone work on that head and swap it out. 

I think for now I'm going to roll with what I've got and focus energies/monies on getting this sucker on the road.  Still have a looonnngg way to go

[siteunseen]

By the time you have the notches cut out, bigger valves and seats done to the E88 I don't think it'll be worth the time and money???  

I would find and N42 like the '75s came with.  That's a good cylinder head.

Here's something I found from a couple of years ago when I was trying to decide on the head differences.  Click on the top, september the 11th reply.