Technical specifications

Does anyone have or know where to find the following information:

- 1982 KZ 1000 (998) J cylinder head combustion chamber size in cc?

- KZ 1100 Spectre (1089) piston dome volume.


I am trying to figure out the compression ratio I will have when switching to 1089 pistons and cylinders using the 1000 head.

All 1000 parts are from a 1982 KZ1000 J motor (998). The 1100 pistons are from (I think) a 1982 or 1983 Spectre 1100 (1089).

The pistons are stock ART pistons.

Thanks.

Do the pistons have 17mm or 18mm pins? J is 17mm and 83 KZ1100 is 18mm while 82 KZ1100 has 17mm pins..

83 KZ1100 head has the bathtub chamber while 82 KZ1100 has the J chamber.

KZ1000 J with 82 KZ1100 piston and cylinder block and KZ1000J head is going to have pretty close to stock KZ1100 compression.

So, to find out what your compression ratio is going to be, just look up the compression ratio for a stock 82 KZ1100 and you'll be reasonably close

I am looking for a better way, but for now, this is what I have tried.

Using a small syringe with a 5 ml mark, I sat the head upside down and leveled it with a level. Then I filled the combustion chamber with vegetable oil one syringe (5 ml = 5cc) at a time. It took 8 of the syringes to fill the combustion chamber. This means that the 1000J head (1982 at least) has about a 40 cc combustion chamber.

To obtain a more accurate measurement, I am planning to find a larger syringe - maybe 50 cc and go through the process again. I think that will be more accurate since I won't have 5 instances of trying to set the syring exactly on 5 cc.

A burette (sp?) would be even better, so if I can locate one, I may try that too.

Next up, pistons. I have a set of KZ1100 pistons that are stock size and are from a 1982 (I think) KZ1100.

A couple of thoughts come to mind for measuring the dome on the piston. First, with some play-doh, press the crown of the piston down into the play-doh until the edge of the piston is level with the top of it. Use a syringe to measure the volume of the depression in the play-doh.

The second is to fill a glass of water to the very top and place it in a bowl. Lower the piston into the glass until the edge of the piston is level with the top of the glass. Then measure how much water was displaced.

My first attempt at this resulted in a very rough estimate of a 10 to 12 cc dome on the piston. I will try this a few more times and maybe try the play-doh method and post a better estimate of the dome size.

Here is a picture of one step of the first attempt.

Here is a picture of the dome.

Now all you need is the compressed head gasket thickness, and the bore size of the head gasket if you want to be really accurate. Going to run the pistons in the hole, or even with the block?

I think I got a larger syringe that measures cc's at a farm supply store, for giving big animals medicine. I've cc'ed a few car heads. Never dealt with domed pistons so I only had to cc the valve reliefs on car engines.

In the hole or flush - that is a good question and one that I have spent some time searching this forum for advice on. There was one thread that stated that Paul Gast (Fast by Gast) recommends 50 thousands clearance between the head and the landing on the piston. If a typical gasket is .040, then you would need the piston .010 in the hole to achieve that. This is contrary to what is generally accepted for small block chevys - generally 35-40 thousandths if I remember correctly.

I wonder if that is because the KZ has more of a hemispherical head. Maybe with a hemi, you don't get the same good effect from squish.

I also wonder if you typically have to run a large gap because the forged/air cooled engine pistons that Wiseco and others make have to run greater bore clearance due to expansion rates and the greater heat variances that an air cooled motor would have. Piston rock in the bore would seem to require more room between the top of the piston landing and the head.

Maybe OEM pistons are cast? If so, would they require less clearance in the bores and enable tighter piston to head clearance?