z1000a1 big bore

[flateddie]

Hi Guys I am looking to finish the engine on my z1000a1 and have reached a fork in the road do I keep the standard head (which needs some work), the original 1015cc barrels stn size with a set of 420 cams I have stored away for a rainy day or go for the Wesco 10.5:1 1075cc kit with a gpz1100 b1 hemi head (with the APE tower already done) which need no work apart from the black paint blasting off and standard cams. Any one out there used either set up. I am looking for a nice torquey motor rather than a drag racer so am leaning towards the 2nd option. Anyone been down the same road?

[garyd]

Don't think there will be a huge difference on performance..the 420 cams might be more up the top.

Using the GPz stuff will cost a bit as there is a fair bit to do to convert the camchain.

GPz will give you the pose value...but I'd stich with the Z1000 stuff as it will keep the original look.

[zed1015]

You could go 1045cc (1st oversize) so you aren't wasting a bore size and there's no noticeable difference between that and 1075.
Also remember that the Geep head will lose you 2 points of compression due to the larger combustion chamber so you will end up at around 8.25 to 1 comp which is a bit low for NA.

Personally i'd go 1045cc and keep the std head and port it.
The 420 cams might be a little hairy for the type of performance you want.

[Pigford]

420 cams are pretty wild & may be best to consider under bucket shims. The GPz head isn't as large as the deeper Unitrak - but I think you may need to allow a bit for decreased compression? The APE chain conversion is easy enuff - just need a jig for the 4 x mounting holes.

Personally I agree with gary - keep the prettier round cam covers and go for a 1075 - bit of head porting and you've got a decent motor. my old Z1000 ran 11.5 secs 1/4's and had 90 bhp at the wheel - nice motor.

[Ginger Bear]

This is the question I posed to Joe Hooper (Pit Stop Performance) back in 2014, with regard to my current project.

Hi Joe,

After doing a little homework, I think I have found the route I want to take with my current Z1000 project motor.

Motor is a KZ1000A2 & looks fairly original. I plan to fit a head from a KZ1000J using APE's tower adapter. Head will keep standard valve sizes, but I am looking to fit a set of your PSP X3 cams & bore the barrels to 1075cc. I have read all about cranking compression on your website & is seem's I need to match the pistons to the camshafts.
In a nutshell, can you quote me to supply a set of PSP X3 camshafts & the correct piston kit to suit my engine configuration?

This was Joe's reply, which I found very useful. hopefully you will too.

Steve
Below is an estimate for you to consider.
The piston kit quoted is what is required to get the proper cranking pressure using PSP-3X camshafts and a J-model head.
The J-model head has a much larger combustion chamber so the J-model pistons are required.
The J-model pistons have a compression height which is 1mm longer than the early style motors.
As such, the pistons would stick out of the bore by 1mm.
That is the reason for the .040" base spacer.
The piston kit comes with one base gasket and I added another so that you can put one on each side of the base spacer.
You have a choice of three head gaskets.
They are one piece copper, one piece fiber and two piece fiber with the chain galley o'ring.
Since you did not mention which you wanted, I selected what I would choose.
You are of course not obligated to go with my suggestions.
I was just trying to fill in the blanks.
I have all of these parts in stock.

[ADE]

Hi
I run a GPZ B1 head on mine with kent 420 lift cams.You will have to clearance the head as the lobes hit the head before the buckets.I also have under bucket shims and orient express valve springs.Before i put the bigger cams i had the standard reprofiled and run 33cr carbs.It made 113bhp at the rear wheel on the dyno.With the nitrous it made 137bhp at 7500rpm then spun the wheel on the dyno just had the one run.Since fitting the bigger cams i don`t know what it makes but it does keep pulling at the top end
Ade

[flateddie]

thanks a lot for the tips guys

[zed1015]

The GPz head isn't as large as the deeper Unitrak - but I think you may need to allow a bit for decreased compression? .

The Unitrack heads twin swirl bathtub combustion chambers are actually smaller than the earlier 'J' type hemi heads putting the compression difference somewhere midway between the early head and the J/GPZ .

The B1 head is full 70mm hemi the same as the 'J' and will lose 2 points of compression if used as stock.

[ADE]

Hi
somewhere in my memory bank i think i used a gpz or j piston kit due to the combustion chamber with 17mm pins.Or i could of dreamt it as it was a while ago
Ade

[neilbarrett]

standard head ,much pritier,ive 1 with stock 1015 pistons ,yosh cams & a set of 33mm crs , .makes 100hp ,