Steam Powered Z???

[240260280z]

btw there is a lot of rust and sludge in that block. when you get it reassembled, flush it well.

[FastWoman]

Wowza! You've had more than your fill of problems with this car! Best of luck with the new head!

[rossiz]

blue - the pictures above of the block are deceiving: the water all over the place was left over in the head and spilled on the block. the rust spot you circled was just a small puddle of rusty water. i've posted a few pics of the block and head below for analysis. my theory is that when i replaced the radiator i had some large air pockets in the system and possibly the pump lost its prime, causing localized overheating/uneven heating and the head warped. i can't find any evidence of head gasket failure and i would think that a crack would have to be pretty big (or multiple cracks) to let that much coolant in that quickly.

here are some pics of the head - i numbered the cylinders w/sharpie:

valves + exhaust 1&2 - crusty white liners

valves + exhaust 3&4 - note different color port liners

valves + exhaust 5&6 - crusty white liners

combustion chamber 1 - note color of valve (this was my best cylinder for compression and plug color)

combustion chamber 2

combustion chamber 3

combustion chamber 4

combustion chamber 5

combustion chamber 6

[rossiz]

pics of the block/cylinders:

overall view - surfaces wiped down, any liquid is excess wd40 sprayed in to keep rust at bay

1&2 - normal carbon, scratches from me scraping off some large patches

3&4 - gray cloud is pitting, i think from lean or water burn??

5&6 - normal carbon

[rossiz]

fastwoman - yes, it's been a journey... but i have to say i'm glad it's happened a little at a time, i was totally confident ripping it apart for the head, as all the systems are much more familiar/de-mystified after diving into them over the past few months.

i chipped out the plaster-like filler that was in the manifold where it was broken under the egr - there was an enormous amount of the crap in there. the stuff towards the exhaust manifold was gray and crumbling from the heat, the stuff inside was brown and crumbling from fuel vapor - what a mess. i'm going to grind down the jagged edges and have it welded shut.

[EuroDat]

If you get a new head get an N42 with no liners to avoid cracks

I agree, but the N47 head will mean you need another header. N47 has round exhaust ports and N42 square. The N42 has better chambers and if its still got the silicon/bronze seats they will need changing.

Another common change is to go to the P79, shave it 2mm, use the N47 valves and shim the cam towers. The P79 seems to have less problems with cracking.

Chas

[siteunseen]

My intake manifold was exactly like yours, EGR tube had burnt at the connection and rotted out the bottom side of the tunnel. I tried to get it welded up but my welder friend said it wouldn't work, too much rot I guess. I found a non-EGR manifold for $50, it was stamped N47 but was some kind of hermaphrodite of an N42. It has the castings of a N47 but no openings from the EGR channel to the intake runners or those big arse allen plugs. I know time isn't on your side but finding a N42 intake would be your best bet, you're going to have to delete that stuff anyhow, thanks to Mr Sawzall for me too, I love those things.

1st pic is the rotten one, stinks too

2nd is the in between N42 & N47

3rd is flowing the mouth out

4th is the difference between the head size and the intake, opened them up too

Nissan had a recall for that tube fitting that comes loose too, I guess our POs didn't get that notice or didn't think it was important.

Edited June 11, 2014 by siteunseen

[240260280z]

#4 intake valve has the most crud caked on it. I think it is the problem child cylinder.

Pop the exhaust valve and clean the carbon to look for a crack below the exhaust liner.

[siteunseen]

Your intake may have been so clogged up it wasn't sucking in any air, vacuum leak style. Mine was and for what short time I drove around with that big old hole it didn't run too well. It had a bad exhaust leak back there too that disguised the rotten intake to my unknowing ears and eyes.

[Captain Obvious]

Take a look at #6 as well. I don't like the way the head gasket has slipped off position and is out of round near the water jacket.

Did you do a compression test before you pulled the head?

[240260280z]

Also there are 2 holes in the gasket between 5 & 6, the one on the manifold side of the block seems to be a blocked up water passage?

[240260280z]

FYI: Challenged writer but apparently he has a Rebello built N42 head if I am understanding the ad correctly:

Rebello rebuilt N-42 9.5:1 to 10.1 comp. - Nissan : Datsun ZCar forum :Nissan Z Forum: 240Z to 370Z