In the process of chasing the exhaust gas in radiator, I pulled the head, gasket looked ok, found a couple areas that may have been a an issue. Anyway while looking over the gasket i noticed several of the head cooling ports on the manifold side were completely covered by the gasket. I pulled out my felpro, it had holes for those but was missing on hole on the spark plug side. Also had holes in the gasket on that same side where there were no ports. 

So what I think is the OE had missing holes in the gasket, the felpro had holes that did not match up with all the water passages either. 

Am I missing something? I have found a OE nissan gasket for the P90a head that looks like the old one, again missing all the holes on the manifold side. I figure I should go that way, even though it seems illogical. 

There was a whole big conversation on Hybridz years ago about head gaskets and holes.  The end impression that I got was that not all of the holes were meant to be open.  You'd probably have to see factory original gaskets to know for sure what the engineers intended. 

The head design in general has uneven cooling as I understand things.  Cylinders 5 and 6 on the turbo engines are the ones that detonate most often.  People took extensive measures to try to improve the cooling, drilling in to the passages and adding a manifold to control coolant flow.  The funny thing was, as I recall, that the guys that got it evened out would just get detonation on all 6 cylinders at the same time.

thanks ZH, think I will just go with the factory gasket then. 

Here are a couple of threads on the topic just to fill it out.  One talks about head gaskets for sure.

https://forums.hybridz.org/topic/59029-head-cooling-on-cylinder-5-solutions/#comments

https://forums.hybridz.org/topic/98875-90mm-gasket-coolant-holes/

 

wow, there is a LOT of discussion in there. Tony D states more holes open the better , think that was the gist of it. 

I maybe getting ahead of myself here, will post up some videos of what I have and have found out. later.

Good news is the bores look great, and the head has less than .003 and that is only at the very end, not the middle. I still have to clean up the head surface, so that may even be false as I may have some residue left on that side. I did a diag check full length was about .002. Using gasket remover and plastic razors for the head, coming out well. 

other issues, the rust accumulation is horrific, I mean like mud like and a lot of it. the block also had one head bolt on the manifold side that fought me all the way out, the rest had nice break away feel. the one that was trouble as the rear dowel hole bolt. Lots of rust. I am pretty sure its a blind hole, so not sure how water could have gotten in there. There was evidence of a brown rust water stain on the side of the block right by this same bolt. Also the fire ring did not have the nice clean space between it and this same area. My guess is the exhaust gases were pushing past the ring and opening up a path from the water jacket, bolt hole, and side of head along the bottom of the gasket. that is what I think i was seeing. 

I bought a thread chaser to try and fix the bolt hole, have a super scraper on the way for the block. I am going to have to pull the engine of the test run stand and either get a shop to hot tank it, if they still do that, or I will pull the freeze plugs and see how much mud I can dig out.

 

 

 

 

I dug into this a little bit deciding which gasket to use on my F54 and I decided on OEM.

My thoughts on the cooling holes is that Datsun was (forever) chasing unevenness in the cooling between cylinders and kept changing the size and existence of the coolant holes accordingly. And by the time they got the to end of the series (which is what you have), they had completely blocked off some of the holes towards the front of the motor with the intent of forcing more water to flow to the back of the head before heading to the radiator.

sounds good to me CO.

Well I decided to just remove the engine from the test stand, will drain the oil and water (with head off), move on to the freeze plugs, and then decide on hot tank or DIY block clean/de rust. There is still about 1" of rust mud (poke s stick down the back water hole in the top of the block). Seems pointless to pursue continued work on the test stand, even if it passed the coolant test I would just tear it down afterward due to the rust issue. I will get the factory gasket, have that ready to go. 

sounds good to me CO.

Well I decided to just remove the engine from the test stand, will drain the oil and water (with head off), move on to the freeze plugs, and then decide on hot tank or DIY block clean/de rust. There is still about 1" of rust mud (poke s stick down the back water hole in the top of the block). Seems pointless to pursue continued work on the test stand, even if it passed the coolant test I would just tear it down afterward due to the rust issue. I will get the factory gasket, have that ready to go. 

Here are my (relatively disorganized) notes about head gasket stuff. Maybe something in here will be of help.

L24 and L26 versions - item #19: (From the old fische)
11044-E3100
11044-E3101
11044-E3102
11044-P3000
11044-P3001
11044-P3000
11044-P3002
11044-P3004 This number supersedes all the previous numbers
and is the final listing for the early motors and its used on 240 and 260

L28 versions - Item #18: (from the old fische)
11044-N4200 - No superseding listed on the fische, but was superseded after the fische

After the fische from other on-line sources
11044-N4200 - 09/1974 - 04/1980
11044-N4210 - 05/1980 - 02/1981
11044-N4220 - 05/1980 - 02/1981  (don't know why there are two of them. Might be turbo)
11044-N4221 - Supersedes all of the above

11044-P7900 - 80-82 GL (turbo)
11044-P7910 - 81-83 GL and non GL (everything 83 turbo and non turbo)
11044-P7911 - Supersedes all of the above

Looks like the 11044-P7911 may have been superseded by 11044-P9600

Part Number 11044-P9600 Replaces NLA 11044-P7900 11044-P7910 11044-P7911
The original gasket was made by NRZ Nippon Reinz
This gasket is made by Stone
It is for the original head/block combo on 1981 1982 and 1983 S130 280ZX"
And if you look closely at the gasket, you can see both the Stone logo and the Nissan logo

victor reinz 61-52115-00 (they list the same gasket for Z and ZX)

Part Number 11044-P9600 is the one I went with, on the way along with an ARP cleaning tap and some new dowel (one got chewed up in the removal process). 

I just finished draining the oil from the block. Coming soon I will cover the oil passages and flip over for some prelim rust removal. just want to get the mud out for now, then will move on to full disassembly for more through clean out and possible electrolysis rust removal (still need to find a shop that I trust, if i can will let them use the method they suggest for cleaning out water passages.

That's the same head gasket I went with as well (11044-P9600). I like the round holes for the head bolts better than the large oversize rectangular cut-outs of the previous version. My thinking is that I want as much meat as possible between the water jacket holes and anything else.

I got mine from Riley at Lynchburg. Out of curiosity, where did you find yours?

And about cleaning out the block... I made a little adapter for a garden hose that shoots a thin jet and I was able to stick it deep into the core plug holes and flush junk out. Kinda like a power washer, but just at tap pressure.

Looks like this: