GPZ750/810 racer running....

turboguzzi wrote:

I am based in milano, where are you? by the way you spell coffie it sounds like netherlands

nice tool, would be great to see how your chambers look like now.

Larry, did a bit of homework and sounds like pressure recovery is what i call the diffuser effect when the gases enter the chamber past the valve. So yes, i am aware of a possible downside, in any case. Still want to keep a good squish band, with the current welding i should get something like 28% squished area. really worked for me in the past.

What i might do, time permitting, is play with plasticine and thread streamers in a spare head to see if there's any point in chamfering only the area near the inlet valve for a bit of a diffuser effect.

TG

That's correct.

There's precious little distance to work with on the chamber side of the seat to assist in that function.

The chamber serves multiple functions. It's possible to focus on only one and loose sight of the others.

You're on the right track. I would suggest making a simple U Tube water manometer with a long thin probe attached.

Blow through the port. Probe on chamber side. Attach a cylinder bore the same size as the one you'll run.

well, as soon i am back home ill post some pics about a strange discovery i made about chamber flow visualization....do hold your breath...

in the meantime, just got from member steell a 810 wiseco kit and the first thing that caught my eye was the flat area all around the crown, which will work perfectly with my approach. i am surprised that nobody took this path before.

fitting that piston to a stock 750 chanber shape will yeld no squish at all. the wiseco slug almost begs for a flat band all around.

also got form him nice looking andrews cams with #30 and #35 stamped on the sides, but no info on them.

does anybody know anything about those kz750 andrews grinds?

i only found info about 900/1000 cams in their site and the grind numbers range only form 1X to 15X, no 30 or 35

Andrews offered the following grinds for the 650/750 Kawasaki

10 - 236 .330 - Bolt in Stock cups & springs 2500RPM+

15 - 244 .340 - Same as above but for 750cc

20 - 252 .350 - Modified engines up to 82 3000RPM+ stock springs and cups

25 - 260 .360 - 82 & Later Stock springs OK piston clearance needs checking more power from 3000RPM

30 - 270 .370 Best cam for big cc street motor. Springs, cups and collars should be upgraded. Power comes on from 3000RPM+

35 - 274 .380 - Street/drags 800cc and up. Fully modified engines run on from 5000RPM up. Springs, cups, collars should be upgraded

40 - 262 .392 - Drags and big motors. Springs and cups required. Broad torque to 11000RPM

thanks injected, that's a start, still have to figure out lobe centers for the 30/35 mix i've got.

will try to contact andrews and see if they have the info

You can try to contact them but I believe you will not get too much info out of them on this old stuff - they only do Cams for Harley's now and you might not get much of a response. The info I posted is all I have ever seen printed.

I have a set of #20's and I set them up by trial and error using the tightest piston to valve I could get (by solder wire) and backing them off a bit (slotted sprockets)

I do the same thing with my race motor, but I monitor cylinder compression between timing changes (after making sure of NO collision) and I set for maximum cylinder compression with maximum piston to valve. I have the timing card for those race cams, but I usually don't put too much faith in those numbers as I believe the two things I set for are more important than achieving those numbers on a card... I do use a degree wheel to record where I am... but this is just the way I do it.

yep, pretty much the way i'do it too, its just that i've been reading so much about 105, 107, 109 lobe centers that it gets confusing

i am coming from a few years working on sohc4's where life is much simpler! (fixed overlap....)

Ok, first to the cams,

Garry @ andrews was kind enough to send me the data sheet, here it is for reference..

the andrews cams were done on impressive aftermarket forgings and garry told ne they would get them from germany at the time and regrind them in the US. So i'll have german cored cams, profiled in the US, picked up in Indiana, running on a japnese bike being raced in italy....

As i have one 30 and one 35, ill use the 35 for inlet and the 30 for ex, the only thing that doesnt sound quite right is that the timing number give 111 lobe centers for both setups, sounds like too little overlap for road racing, i hear people here running 105 even, could be great to hear your reccomendations.

now to this pretty interesting discovery...

was drying some parts I washed with a blow torch, the head was nearby and i got this stupid idea....

did the same on the ex side....

nothing reall ynew here but i thought its quite nice how well you can see the flow pattern and the sad fact that the bottom of the inlet doesnt flow much at all. more to the point, regarding larry's comment on pressure recovery, most of the flow seems to attach to the chamber roof, very little of it touches the chmaber edges (which i welded), so my hunch is that there's little influnce of the squish band angle on flow past the valve.

on the exhaust side, quite impressive how the floor of the port (white line) doesnt get any flow at all. no wonder so many tuners D-shape it.

not bad way to viusalize stuff for 0$

TG

I keep hearing Beavis chanting Fire, Fire, Fire...

Neat photos none the less.

turboguzzi wrote:

in the meantime, just got from member steell a 810 wiseco kit and the first thing that caught my eye was the flat area all around the crown, which will work perfectly with my approach. i am surprised that nobody took this path before.

fitting that piston to a stock 750 chanber shape will yeld no squish at all. the wiseco slug almost begs for a flat band all around.

Funny you should mention that. I have my 810 pistons in a KZ650, with a 650 head, and it will have a good squish area since the 650 chambers are smaller than the 750 ones.