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thats what i figured by looking at the combustion chambers,just couldnt remember which it came off of a j or gpz.i did that head for one of my 1170 motors backin late 80s-early 90s.its got your stainless valves and springs and cam chain adaptor and a bunch of other goodies i bought from a crook shop here in omaha that went out of business a few years ago;)

Thanks guys thats great stuff.So If I realy wanted to build the ultamit KZ.I would be better off going with the 84 gpz cank and head to get the very most out of the motor in the end.

wireman wrote:

the j/gpz head will outperform the average ported kz head right out of box,a ported j/gpz head will really move a lot of air/fuel;)

A KZ head with stock 36mm valves can be ported to outflow a "stock" late model GPz11 head at peak lifts. The GPz head with the larger valves will outflow it slightly at lower lifts. Installing 37.5mm intakes in the KZ is the way to go when having it ported if you want the most out of it.

PS....Wireman...the one photo you posted shows me you're on the right track...nice job!

Post edited by: larrycavan, at: 2006/11/14 23:44

Larry now you’ve a lot of good stuff here.. . but you didn’t mention the 83 -85 gpz ported with bigger valves? How does it compare? Is there much dif?
I have 37mm intakes and ported now

83-85 GPz / 84-85 LTD - Intake runners are considerablly larger with the largest intakes and exhaust valves Kaw used on any of their KZ or J motors. Outflows on avg 10cfm @.400" lift /10"Pressure] more than KZ or J. 82 vs 72

Standard J head from any model exclusing above, 1mm over valves, runners are larger than KZ but on average doesn't flow anything to write home about..Low 70s at above test pressure and lift.

the j/gpz head will outperform the average ported kz head right out of box,a ported j/gpz head will really move a lot of air/fuel

A KZ head with stock 36mm valves can be ported to outflow a "stock" late model GPz11 head at peak lifts. The GPz head with the larger valves will outflow it slightly at lower lifts. Installing 37.5mm intakes in the KZ is the way to go when having it ported if you want the most out of it.

larrycavan wrote:

wireman wrote:

the j/gpz head will outperform the average ported kz head right out of box,a ported j/gpz head will really move a lot of air/fuel;)

Installing 37.5mm intakes in the KZ is the way to go when having it ported if you want the most out of it.

<br><br>Post edited by: larrycavan, at: 2006/11/14 23:44

I agree. 37.5 intakes in a KZ really wakes it up. The later heads can take 38.6 and 33s on the stock seats.

Jay

What was the first year for the J-Head?

Jay-
Does APE sell the 30t sprockets so I can use the J camshafts?

so are you saying the gpz with 38.6 is the best.would I notice much of a diff. over mine being ported with 37 intakes allready?what would the next logical step be for me?



I agree. 37.5 intakes in a KZ really wakes it up. The later heads can take 38.6 and 33s on the stock seats.

Jay[/quote]

Mark,

Yes the late model GPz11 head, ported with stock valves can easily have another 15% flow gain. It is the superior head to all KZ/J series heads.

Keep in mind that it's not just bulk flow that colors the picture on heads.

Back in that mid 80's I had a conversation with a guy that had a couple of the heads that came off Eddie Lawson's factory superbikes. He worked for Kawasaki. He made his way to the dumpster when the team was disbanned and as the parts were being tossed in, he simply helped himself.

The heads flowed suprisingly small amounts over a stock GPz11 head [the head that was modeled around those championship winning heads]. Regardless of the unimpressive CFM number, the heads made good power because it was the total package that worked.

The most common things I have seen in Kawasaki heads that have passed through my hands and onto my flowbench is over ported exhausts and intake runners cut very large without any of the additional porting work that makes the real flow.

yep bigger isnt always better,especially if the motor doesnt spend anyime in the rpm range all those prostock style parts are designed to work at;)

A total engine combo package should be looked at Mark. But based on what I've read regarding the work done to your bike so far and not knowing any flow or port velocity numbers, there are 2 things I'd consider.

1. 34mm flat slide smoothbore carbs
2. APE's K410 cams [can you say mid-range;) ]

Moving to a J head is not the most logical next step if your KZ head is ported correctly. It's an expense you probably don't need to incur.

Duck wrote:

Jay-
Does APE sell the 30t sprockets so I can use the J camshafts?

No. Never any demand for that combo. We used to do a 32T when funnybikes used to run those cams, but that died also.

Jay