'75 280z - Head temp sensor question

[Zed Head]

4 hours ago, Neb said:

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

There is a dimension for the thickness of the head that you can measure.  From top edge to bottom edge.  4" plus a little more if I remember right.  I'll see if I can find it but somebody here might have it on the top of their head.  You might just measure yours and post it, and somebody can verify, or even measure a head to compare.  I have one in the garage.  They're all the same across the years because the same cam timing gear, chain and sprockets, is used on all of them.

[Zed Head]

Here's a link that seems to cover everything including a way to possibly get the wrong number.  Looks like 108 mm is the number.  Norm the 12 Second Dude was deep in to L series engines until he crashed his Z and sold it.

http://www.zcar.com/forum/10-70-83-tech-discussion-forum/123994-stock-head-thickness.html

[Neb]

2 hours ago, Zed Head said:

Here's a link that seems to cover everything including a way to possibly get the wrong number.  Looks like 108 mm is the number.  Norm the 12 Second Dude was deep in to L series engines until he crashed his Z and sold it.

http://www.zcar.com/forum/10-70-83-tech-discussion-forum/123994-stock-head-thickness.html

So from that it sounds like the original height is 108mm.  I measured 106mm on my head (measured height both sides, 3 places ea).  So from what I gather this head has L28 valves, and is 2mm shorter.. but there are no shims on the cam towers so wouldn't that mess up the timing chain? 

Edited March 30, 2018 by Neb
grammar

[EuroDat]

24 minutes ago, Neb said:

So from that it sounds like the original height is 108mm.  I measured 106mm on my head (measured height both sides, 3 places ea).  So from what I gather this head has L28 valves, and is 2mm shorter.. but there are no shims on the cam towers so wouldn't that mess up the timing chain? 

Yes that would mess up the valve timing.

Now the real question. What valves did they us in this head when they fitted the L28 valves?

Normally when people do a head upgrade with a P79 or P90 (turbo head). They then shave 2mm of the head to raise the compression, add 2mm shimes to the cam towers to correct the valve timing and fit the valves out of a N42 or N47 head. Yes those valves have two mm longer stems.

If your head doesn't have shimes, I persume it has the valves for the P79/P90 heads. You would then need an adjustable timing gear to correct the valve timing.

I have the length of the valves written down somewhere. Ill dig it up and post it later.

[Zed Head]

That head kind of looks like somebody's past experiment, that they tried to run and didn't get quite right.  There are many moving parts that have to work together.  But, I think that I can dissuade you (been waiting to use that word...) from entertaining the thought of putting that head on your engine, unless you want to spend quite a bit more money and time on it.

Look at the cam lobes.  The rocker arms are probably similar.  You might just have a collection of parts thrown together>  The bluing on the valve seats looks unrun, but there's no reason to put that camshaft on a head you're going to use.

[siteunseen]

Looking at that cam he'd be easily dissuaded.

[Neb]

  I hadn't even noticed how worn down that thing was.  Consider me dissuaded!  Now I gotta figure out what to do with it..

 

[siteunseen]

Try and sell it then get a 280 head. Easiest path in my opinion.

Like Zed said get a p79 and have it cut then put '75 to '78 valves in there. 

Here you go,

http://datsunzgarage.com/p79/

[Zed Head]

I think that EuroChas implied that, not me.  Neb is making fantastic progress, he'll probably come up with his own plan pretty quickly.  Lots of options, from building an engine in the "meantime" to swapping heads, to swapping engines.  Many of us have the parts for those options in our garage or sheds.

I ponder those options occasionally then take the car out for a drive and decide that it's fine like it is.  It  can sit for a while and start when it's supposed to, and it doesn't break down.  And it's fun to drive when I drive it.  That's the goal I set when I started.  I had my crazy days back with the GTO and Pontiac 400.  Can't fault anyone who takes a different path.

[EuroDat]

Wow, that cma looks really bad.

When you start playing with these engines, you will find lots of combinations to chose from. Everything from conrods to even using vw golf pistons.

I remeber having this discussion about the valves years ago. And a members machine shop mixed up the diferent L28 valves when they replaced a couple. If you use a general machine shop, YOU need to know a lot about these engines.

Here is a thread about the problems Ben was having. I admire Ben's resolve to finish it.

 

[siteunseen]

5 hours ago, EuroDat said:

If you use a general machine shop, YOU need to know a lot about these engines.                                                                                                                 

Can't add to the quote for some reason?  My machinist says he has done so many of these engines he knows them inside and out then calls me for information.  He said he hadn't touched one in 25 years! 

Edited March 31, 2018 by siteunseen

[Neb]

On 3/29/2018 at 7:02 AM, 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.

sorry to resurrect.. but today I had the exhaust manifold off and the square manifold will indeed cover the round ports no issue!