TOPIC:

These three groove cams seems to be from 82 KZ1100 B2 288 degrees with .346 lift.


​​​​​​My '81 GPz1100 B1 has those "3 groove​​​​" cams, on intake and exhaust. (the same sprockets are also used, just using different bolt holes)
From my research, they were used on 81 and 82 GPz's, and also the '84 1100R (Lawson Replica)

H.

These three groove cams seems to be from 82 KZ1100 B2 288 degrees with .346 lift.


​​​​​​My '81 GPz1100 B1 has those "3 groove​​​​" cams, on intake and exhaust. (the same sprockets are also used, just using different bolt holes)
From my research, they were used on 81 and 82 GPz's, and also the '84 1100R (Lawson Replica)

H.

Exhaust
​​​

Intake
 

I started to do some math here for the piston/head setup. So I have 70mm pistons 10:25;1 set. I tried to measure piston and head with following results:
Piston crown: 15,6cc
Head combustion chamber 40cc
Head gasket 4,6cc

Real combustion chamber: added gasket volume and reduced piston crown: 40+4,6-15,6=29cc
Compression ratio:
(29+253,8)/29
282,8/29=9,75

Is this OK? I was expecting a bit lower compression ratio? of course I might have made some errors with my measurements... 

Rc900 wrote:

I started to do some math here for the piston/head setup. So I have 70mm pistons 10:25;1 set. I tried to measure piston and head with following results:
Piston crown: 15,6cc
Head combustion chamber 40cc
Head gasket 4,6cc

Real combustion chamber: added gasket volume and reduced piston crown: 40+4,6-15,6=29cc
Compression ratio:
(29+253,8)/29
282,8/29=9,75

Is this OK? I was expecting a bit lower compression ratio? of course I might have made some errors with my measurements... 

Stock Z1/Z1000 head is 36cc and just dropping on a J/GPZ 40cc head drops the comp approx two points so 10.25 ends up around 8.25.( good for a turbo build you may want to easily put back to N/A  at a later date )
1015cc divided x 4  = 253.75cc ( one cylinder ) .
253.75cc ( one cylinder divided by 66mm ( stroke ) = 3.84 cc
1mm of stroke = approx 3.84cc 
Skimming the head approx 1.3mm ( to allow for curvature of the hemi chamber ) brings the volume back to approx 36cc and the comp back up to approx 10.25 ( or the stated comp of the Z pistons to be used ).
Zero the deck height and CC the chamber to 36cc for accurate results if fractions of a point and true 10.25 or stated piston comp figures are important.


 

Yes, thank you. My English is not good enough to understand everything… Hmm, more math… Better than my last one:

One cylinder size:  35mm*35mm*3,14*66mm=253,8cc

Calculating the combustion chamber size with stock head, piston crown reduced. Now we know that compression ratio should be 10,25 with my pistons, so
(253,8+x)/x=10,25
253,8+x=10,25x
253,8=9,25x
x=253,8/9,25=27,43

So the empty space between piston and head (i.e combustion chamber?) should be about 27.43cc with stock head and wiseco 70mm 10:25 piston set. If we know that chamber in J head is 4cc bigger compared to z1 head, we can calculate the compression ratio with J head (with same pistons) just by  adding this 4cc to known 27,43. I.e. So the combustion chamber with J head got to be 31,43cc. Now we can calculate the compression ratio for this head

(253,8+31,43)/31,43=9,075

So I guess that the compression ratio gets reduced about 1,175 "units".
Or did I do something wrong with this calculation? 

9,075 would be a bit better that the original one, but I really liked to get more that 10 out of it. So got to check if it is somehow possible to get that one extra mm away from the head.

Rc900 wrote:

So got to check if it is somehow possible to get that one extra mm away from the head.

There's room to skim 1.3mm and a bit more .
I've done this a few times.
The GPZ valves are also 1mm further into the head  with 1mm shorter stems so they end up the same distance from the Z pistons as the stock Z valves. 

i'm impreset of the acknowledge you has!