TOPIC:

oops. typo. 38.6 intakes

kaw-a-holic wrote:

tomsbadkz wrote: This is the head that LarryC did for me for 77 KZ1000 project. mine flows over 100 cfm. best head you can use unless you go for an aftermarket head. we did valves and web cams on mine.its going to be a fun ride.

What all did you do to make that head work on your bike?

Note the OE Std J piston...should work, right?

with building my motor, I had to get 83-84 gpz1100 pistons from MTC. they have the 17mm pin. with adding approx. a .040 spacer under the cylinder, these are the pistons I was told to get. I think there is a slight different valve angle on the 83-84 head. u could check with larryC or call MTC. they have knowledgeable people.

daveo wrote:

zed1015 wrote: Which engine do you want to fit it on.
Be careful with piston to valve head clearances on assembly.
Depending on application you may need to fit different pistons or machine the valve pocket angle to avoid collision etc.

The engine is a 1982 KZ1100-A2 with stock J pistons.

This beauty has shim over buckets with standard J cams.
I was hoping for a simple, straight forward head-swap...now

OE Standard piston I want to use...if possible.

It is the different angle and size of the valves which may cause problems and you need to make sure they do not clip the piston crown.
You need to dry build and cam time the top end with the cams you intend to use.
you can just fit one bare piston, no rings or circlips. then rotate the engine slowly while observing the valve movement through the plug hole and their proximity to the piston crown.
If there is no contact you then need some plasticine placed under the valve head which will get compressed and you take a measurement off that to see how close things are and then you can decide which approach to take.
If using stock pistons you may just bolt the head on with no problems but a higher crowned Wiseco piston etc may need the valve pockets re-angling or fit a piston intended for the model the head came off.

Thanks zed1015
So I may be ok with the stock pistons? That would be just the ticket for me. Notice in the photo how the stock piston dome is bathing (completely submerged) in the tub, without a head-gasket. That's a good sign, isn't it
How about this? If I carefully mount this head on the block after removing the existing 82 J-head from the motor, and lightly fasten it down on top of the old head gaskets...then carefully attempt to install the cams per shop manual directions. If they bolt in without getting held up by a valve, I'll be good to go on to the "look through the spark-plug hole" idea.

Well, Vance & Hines said there was no way I'd be able to install a 13009-J header/muffler on my bike

You won't have any clearance issues with the piston crown and combustion chamber even if you assembled with no head gasket.
The GPZ pistons had a higher dome than yours anyhow.
It's just the valve angle and larger valve heads that need to be watched.
Your plan to switch heads and drop in the cams is as I suggested and you will probably be good to go and you get a slight compression increase for free in the deal.
With the valve angle being steeper ( more vertical ) this tips the edge of valves further away from the pistons edge but brings them closer at the crown.
Using the std piston with relatively low dome there will probably be plenty of clearance I would guess.
I have only ever built performance motors using these heads with either turbo or hi comp pistons and never just swapped the head on a std 'J' so can't say for certain.
Maybe Larry or someone else here has just done the basic head swap and can confirm that no further mods were needed.

zed1015 wrote: It's just the valve angle and larger valve heads that need to be watched.
Your plan to switch heads and drop in the cams is as I suggested and you will probably be good to go and you get a slight compression increase for free in the deal.
With the valve angle being steeper ( more vertical ) this tips the edge of valves further away from the pistons edge but brings them closer at the crown.
Using the std piston with relatively low dome there will probably be plenty of clearance I would guess.

Cool...baby! One other thing...do you think a set of 84 GPZ cams might work in there, and (if so) could I expect any performance increase by using them vs. J-cams?

Yes! the 1983 onwards GPZ1100 UNITRACK cams are bit sportier with more lift compared to the J cam so will perk up the motor a bit.
Obviously that extra lift will make the valve run closer to the piston so more attention needs to be made in that area to be sure everything misses.

zed1015 wrote: Yes! the 1983 onwards GPZ1100 UNITRACK cams are bit sportier with more lift compared to the J cam so will perk up the motor a bit.
Obviously that extra lift will make the valve run closer to the piston so more attention needs to be made in that area to be sure everything misses.

One pair of GPZ cams on the way, baby!!!

...

daveo wrote: ...

Decisions, decisions...
With 1984 GPZ cams and sprockets, I clayed the unmodified stock piston and got this:





First time for everything. Nothing ventured...(definitely) nothing gained!