Hi, im rebuilding my ZE head due to excessive oil use and the fact that im going to install new valve springs and cams anyway.
I have just a few questions tho - does anyone heard of ndc bearings? Currently i can only find them for the con rod bearings and i am not very sure if they are worth it. My other option is to order KING from ebay, anyone used them?
Also i am going to use head gaskets, valve seals and head bolts from elring - i think they are good brand, what do you guys think?
Piston rings will be most likely TPR, should be fine, i think...
Could anyone recommend any mods while the head is off? So far i will make myself phenolic spacers, not sure if porting the head will be worth the money?

I think there is not to much you can do besides porting the inlet manifold and making sure compression is good. (Which ofcourse you do by installing new piston rings and new valves etc.)

I would consider buying thermal spacers for the inlet manifold to lower the intake temp. That's about it I think. You cannot increase compression by a lot because it is already quite high.

Thanks for the info! I have access to CNC shop and the phenolic material that is used to make those spacers, so i think i can make them for under $10-15.
From what i've found on the forums, most compression that can be achieved within the safe zone is around 10.5:1
I'm also considering replacing only the valve seals at first so i wont have to remove the head, do you think its worth the try? The car is burning like 1L per 1500km, the smoke is constant during drive, it increases with acceleration. Its not visible from my driver position, but people driving behind me see it clearly. I don't see any blue smoke when driving downhill in gear and pressing the acceleration pedal after the decline -my old KF smoked like crazy in this situation and the smoke was clearly visible from the car while driving.

Does anyone know what is the ZE piston diameter? I cant seem to find that info anywhere on the web

I think they're 84.5mm... based on the Wiseco pistons with a standard bore

http://www.importperformanceparts.net/i ... mazda.html

EDIT: http://mazda626.net/topic/37114-klde-vs-klg4-vs-klze/ seems to agree that the KL block is an 84.5mm bore
EDIT: and here http://www.oocities.org/viv95pgt/klze.html

What do you mean you couldn't find it? I googled "mazda klze bore" and those two were within e first 4 links

I mean the piston diameter, not the cylinder. I would like to know if my pistons are worn, because i can see some slack between the pistons and the cylinders, which doesnt exactly look normal according to my mechanic, but the car has good compression and overall the engine is in very good condition, also the honing on the cylinders is intact. Im not really sure if there is a problem or not, because the slack indeed seems kind of big and my mechanic freaked out at first, but from pictures of rebuilt klze's i found on the net, they all seem to have that same slack... If i can compare my pistons to the stock ones that would really help clear things out.

On another note, is it possible to avoid the re-torque of the head bolts ? Having to re-torque would be a nightmare, as you have to take off the IM, timing belt and cams off again...

You don't do a re torque.
The Head bolts are the tension type.
You do them up to xx nm and then do 90 degree turn and then 90 degrees turn again.
Then they are done.
Always use new bolts.
There are two lengths of bolts but either are OK for the K series engines.

I rounded my cylinder faces while the head was off, to explain, the cylinders on the block are perfectly round but, the head is a sort of squashed cube shape, I placed new head gasket on the head and marked around the shape, there is a lot of metal you can grind away therefore increasing the overall displacement, i tested that i had the same displacement in all 6 faces using a ink refill syringe as it was marked with ml marks so i could get them all equal. also soak the valve stem seals overnight in oil before fitting because they can become brittle and not seal properly at first.

The thermal linear expansion for the 2 metal is different so the forhead and body of the piston is with decreased size so it didn't stuck in the cylinder when the engine T rises.
The size could be measured from a new(never instaled) piston (from a shop) for example
When cold the molecules of the piston are arranged densely, when hot they absorb the heat(energy) and they use more space so to oscilate.That way the forehead and all the body of the piston when heated gets "bigger" (changes it's size) BUT there is maximum for the size it gets.
When overheated(above work T) the piston could scrape the cylinder..
So when the engine was designed,that work T size is persued so the engine has the best compression and no risk of damage..
With time the piston could get a little wear but not much
and it could be measured with micrometer.
Also the cylinder changes it's size and makes it's own contribution to the sealing of the chamber.
Sawo, try looking for new piston in some parts shop and ask if they can measure them for the size,
but i doubt that they will give you the right numbers.

Thanks for the suggestions - I've been thinking about this for quite some time, but gave up eventually. I reassembled the engine with the original pistons and now after 25k km everything is still going great. No oil consumption and the compression was measured recently - almost identical on all cylinders which is great.
Here is some info for anyone interested:
At first i tried sourcing the OEM pistons - i found the original numbers on the ZE pistons, but mazda doesn't make them anymore. Asked different places, mazda Japan - no luck.
Then i decided to see if i can get everything forged - pistons, rods, etc.
The offer i got from H-P-C.nl was ~1000eur for 11.5:1 wiseco + skirt coating + piston rings; ~720eur for H-beams; these with full gasket set, racing bearings for everything and few other things totaled about ~ 2700eur with the VAT included.
Of course cheaper gaskets and few other things can be sourced, but still 2500 eur is about what you have to pay.
I was almost about to purchase everything when i found something i've been missing. When you introduce changes to your rotating assembly such as new pistons, rods and everything, the crank needs to be re-balanced so you don't wreck your engine. Several people told me you just need to weight-match the parts but that is simply not true. You need to weight the rotating assembly for each cylinder, attach the same weight on the crank and then balance it. Only then you can ensure long life of the engine. I have seen to many rebuild horror stories on the USA forums to fall for this and blow so much money for nothing.
Unfortunately i haven't found anyone here in Bulgaria to do this kind of balancing, so i asked H-P-C who were extremely helpful already and offered to re-balance my crank for 450eur. That is pretty high price as they agreed, but it's not something you can do in your local shop.
That meant i had to open the engine, send them the crank, wait for it to get balanced with all the parts, pay high shipping prices and so on.
H-P-C found solution again - they found ZE crank - that way i can skip on time and shipping costs, but the price of the crank itself was high, so they tried to find DE crank, which is exactly the same, but haven't managed to find one yet.

At this point i think I'm going to drive the car as it is and stop blowing insane amounts (compared to our country standards) of money for things that aren't really worth it. In my opinion the only way to properly rebuild that engine with new, stronger and lighter parts is going through the above steps. That means one would have to pay roughly 3 to 4,000eur for parts and labor. I just haven't invested enough in this car to justify such expensive rebuild for N/A car.

Hope that info helps anyone willing to go down this road.