Best combo of engine motor types that can be done

Here was a question batting around my brain after reading some hop up threads, larry Cs posts on the differences between Mk I, Mk II and the J motors, and also reading some stuff on the APE site.

i got to thinking, if you had a pile of all three of these motors, how should they be combined to make the best possible motor, wieght, quick revs (low reciprocating mass) block strength to handle HP, longest lasting, most HP as possible and still be streetable

Say, like Z1900 crank, MK II block, J heads as a discussion starter.

Money is not an object?
J crank with 16 tooth center pin. MKII cases. J head. 83-84 GPZ 1100 trans converted to KZ cases.
To be honest the J motor is best all around and would be cheaper in the long run just build the bike around that.

It's a "jus for fun" topic :laugh: My own build is going to be in Z1 cases, Z1 crank, Z1 motor really, just 1100 ish and mild cammed, Larry ported head FYI.

I am just curious as to the possibilities after reading some posts on the matter

etbike3135 wrote: Money is not an object?
J crank with 16 tooth center pin. MKII cases. J head. 83-84 GPZ 1100 trans converted to KZ cases.

Same as above but shim under unitrack twin swirl head.

zed1015 wrote:

etbike3135 wrote: Money is not an object?
J crank with 16 tooth center pin. MKII cases. J head. 83-84 GPZ 1100 trans converted to KZ cases.

Same as above but shim under unitrack twin swirl head.

I am not familiar with this head- please elaborate? Can it be addapted to non-J motors?

The unitrack head was an improvement on the 'J' and bolts straight on the early engine with the same APE (or similar) top idler conversion as needed for the J head.

Although almost externally identical to the 'J' it features larger valves (at a slightly steeper angle)and larger factory ported inlet tracts as well as a twin swirl combustion chamber (bathtub) and smaller shim under bucket shims as used on the earlier 650/750's.

The combustion chamber volume is also slightly smaller than the 'J' so the initial compression drop is not as pronounced if fitted with no piston changes but you do have to be wary of possible valve to piston interference due to the different valve angle and compensate for this by possibly having the recut the valve reliefs in the piston crown.
The same twin swirl head was used on the later z1100s (spectre etc) but these reverted back to the larger shim over bucket valve adjustment.
The unitrack heads are much sought after and go for good money but it is an unkept secret that the later z1100 ones are the same and the ones to look for at a much cheaper outlay and can be converted to shim under using z650 valve train parts if required.

Interesting- I had no idea. I think I will have to keep an eye out for them. A rule of thumb for any engine build is that the head is what really determines HP. Longevity is in the bottom end, but HP is in the top end is what my racer uncle used to say about his Mopars LOL

When you say Z1100 are you talking GPZ 1100 or KZ1100 or just a J head in particular? Thats for the education LOL

Iam currently running mk11 cases mk11 welded crank and backcut trans and a ported J model head all on a set of 80mm mtcs and 3x cams and 36 flatslides. I really like my combo more being a street only bike. No problems with over heating so far. The bike has a extreme amount of power.

Well since it's your $$$... :laugh:
You guys forgot to mention Head work (Stage 3) requirements: over sized valves and porting...
If it can't flow, she wont go.....

Wow, I am really going to have to reconsider using the stocker heads and go with these J heads LOL

CruisingRam wrote: Interesting- I had no idea. I think I will have to keep an eye out for them. A rule of thumb for any engine build is that the head is what really determines HP. Longevity is in the bottom end, but HP is in the top end is what my racer uncle used to say about his Mopars LOL

When you say Z1100 are you talking GPZ 1100 or KZ1100 or just a J head in particular? Thats for the education LOL

I think he Is referring to the "83 - "84 GPZ1100 head.

Which is my choice since I have the whole engine.
Plans are to bore it 1.0 over,already have the new factory pistons and rings.
Mill the heads and block just enough to sguare them and raise the static comp. ratio a little.
Degree the stock cams.
Crank, already welded.
Trans, back cut with heavier gears.
Almost new RS34s and factory Kerker hanging on the wall.

Now I just need to find a nice J model to put it in.

Yes! the GPZ1100A unitrack head.
The later z1100's are a combo of 'J' bottom end and superior GPZ style bathtub head.
They reverted back to shim over bucket on those as they were in a lower state of tune with milder cams.