Differences between the Z1/KZ900 and KZ1000 cylinder block for big bore

I would like to know if there are any differences between the Z1/900 cylinder block and the KZ1000 cylinder block.  

Assuming one was going to resleeve the block for a larger bore (say 73 or 74mm), would there be any advantage to using a KZ1000 cylinder block over a 900?  Did Kawasaki increase the size of the fins or add material anywhere for the 1000 cylinder block?

Looking at the Wiseco catalog, they say their kits will fit anything from 73 to 80, the only different being when a new sleeve it required.  It looks like they offer a sleeve (P/N ka629sl) for use with a 73mm (1105cc) to 76mm (1197cc) bore.

I picked up a GPz1100 bathtub head, so I'm curious about kits above the typical 1075cc.  I have a few 900 blocks I got from my dad.  I'm wondering if those would work as well as anything else with the larger sleeves.

Also, to ask the much debated question, at what point does cooling become an issue?  Say if I were to bore the 73mm sleeve out to 74mm and use 1135cc Wiseco pistons?

And then there is the issue of how to get pistons that are correct for the bathtub head combined with an early motor.  I've read many posts about this combo, but no one mentioned where the pistons come from.  Do you call up Wiseco and ask for a custom GPz shaped piston with the KZ1000 wrist pin size and location?  Does someone make this part?

Schnitz Racing 
The J model heads are suppose to lower compression ratio about 2 points.

The sleeve required for a 1197 piston (71-76mm) will break out when bored into the 903cc barrel. It will go into the 1015cc barrel and not break out because there is more aluminum around the stock liner. The next size liner will break out of the 1015 barrel so anything over 76mm will require a billet barrel (big block)
The standard liner in the 903cc barrel will go to 1045cc maximum (71mm) The standard liner in the 1015cc barrel will go to 1105cc maximum (73mm)
As long as you can maintain adequate liner thickness cooling will not be a issue unless you live in a warm climate. If you have less than .100" liner thickness you will probably require a oil cooler.
You can skim the cylinder head to bring the compression up but you need to make sure you maintain a adequate combustion chamber volume, the rule of thumb is to be able to move the piston around in it by hand, if it does not move then you will need to make corrections somewhere.

For the 1000 Block a safe , long lasting  motor size is 1075cc's.
It will give you long service even on high power / compression / boosted  applications ...
You can always go bigger  , but at the cost of reliability 
Dave

The liner that breaks out on a 903cc block is 3.200" OD, the next size liner is a 3.275" OD, the next size is 3.465" OD (1327-1428cc)

When you go bigger than a 73mm piston it throws everything out of wack, requiring bigger ports, bigger cams, bigger cams, and bigger carbs.

wrote:

The sleeve required for a 1197 piston (71-76mm) will break out when bored into the 903cc barrel. It will go into the 1015cc barrel and not break out because there is more aluminum around the stock liner. The next size liner will break out of the 1015 barrel so anything over 76mm will require a billet barrel (big block)

Is that correct?  My dad's Z1 is at or above 1200cc, and I thought that was using a 900 block.  I'll have to go double check.  

The standard liner in the 903cc barrel will go to 1045cc maximum (71mm) The standard liner in the 1015cc barrel will go to 1105cc maximum (73mm)

Wiseco used to have more clearly stated recommendations on their page, but those seem to have gone missing.  I recall they also recommended 1045 max for the 900 sleeves, but I thought they suggested 1075 max for the stock 1015 liner.  In the current catalog they seem to recommend  72mm (1075) max for their own smaller sleeve (KA627SL).

You can skim the cylinder head to bring the compression up but you need to make sure you maintain a adequate combustion chamber volume, the rule of thumb is to be able to move the piston around in it by hand, if it does not move then you will need to make corrections somewhere.

Given how much larger the bathtub combustion chamber is than the hemi Z1/KZ, it seems like the best case would be to use a piston with a dome designed for this combustion chamber.  When folks make a hybrid engine, do they typically use KZ pistons?  Why not use GPZ pistons adapted for the KZ rods?

Maybe this will help
kzzone.com/pistons.html
I run a 1075 in a kz1000 block
MTC pistons  ( I smoked my last 2 sets of Wiseco"s )
30 pounds of boost ( Not all the time , )
Dave

wrote:

30 pounds of boost ( Not all the time , )
 

Nice!

Here are some more references.
www.aperaceparts.com/tech/techkz1000.html
www.kz-1000.net/post/130285291257/faq-ab...kz900-kz1000-engines

And some more discussion about bore sizes: 
www.kzrider.com/forum/2-engine/269571-10...ed-to-sleeve?start=0

I miss Larry C.

My machinist says that some 903 blocks will take the 3.200" liner but the majority won't.
I don't know which ones will, but he says its too risky to put the time into the wrong one to find out, so just stick with a 1015 block as its a sure thing.

I know all about this 1197 in a 903 block because I am currently having to scrap such a barrel with broken out fins on it and redo everything in a 1015 block... only thing I can reuse are the pistons.

The 1260 uses a bigger liner still, sort of in between the 1197 and the 1327 size. No way the 1260 could be put in the 900 barrel.

As for those sizes I listed they are absolute maximums, more for drag racing than street riding (less than .080" liner thickness) I would always revert to a smaller bore and thicker liner for longer life (+.100")

The 810cc kit for the GPZ750 only leaves a .050" thick liner and plenty run that even thought APE says no. Its funny how Wiseco no longer supplies the 720cc kit for the 650 even though the liner was thicker (.070") than the 810 kit - Can't figure out why the 810 kit is still out there.

It was mentioned on here a few times that the GPZ head required +.100" to be removed from the deck to get the compression back, there is plenty of meat on those heads to do this. Its too expensive to design a special piston dome to accommodate different bore sizes, custom pistons the last time I looked were over $1200 a set.
 

wrote:

My machinist says that some 903 blocks will take the 3.200" liner but the majority won't.





 

Every Z1/900 block i have had is the same casting and external thickness as the 1015..
They are basically the same 900 casting bored out for the larger 1015 liner with the difference being the stated capacity on the front right.
They will all take a 1200 liner but will break through the casting in some places when going to 1260.
This has been the case on every 900 block we have done and is why 1200 is the largest liner you can usually now find for a stock block.
Personally i wouldn't bother going bigger than 1075 for any state of tune on the road.
This happens to be the sweet spot for these engines and going much larger offers diminishing returns with little advantage overall.
 

If I were purchasing the pistons new I probably would not go above 1075 either.

On the other hand I bought the 1197 kit ready to go (with broken out fins) for $125... The pistons alone are worth +4 times as much as I paid for the whole package. I am just trying to salvage what I can for as cheap as I can do it.

I’m not an engine builder but I believe own eyes.