GPZ head on early Z1000 engine - Anyone done the conversion, is it worth it?

[Guest]

Hi all, i have the chance to buy a GPZ cylinder head for reasonable money to go on my Z1R, from speaking to Steve Debben it`s not an easy swap as it is the bi-spherical (?) combustion chamber type which will need a lot of machining for my high compression pistons. I mainly want it for the shim under bucket, and also because i`ve been told it`s the way to go to get more power. My options are:
1. Buy the head, get it modified, fit some hairy cams that i already have, see what the result is (empty wallet?)
2. Buy it anyway and use the shim under buckets in my early head and then fit wild cams to that. Are they compatible?
3.Don`t buy it, but buy APE buckets and titanium retainers, (big bucks) and fit into my early head.
4. None of the above and spend the money on porn.
Also when taking the head off, is that going to disturb the barrels so that they will need to come off and be re-sealed as well? Something simple always ends up getting complicated and costing lots of money!

[mikey]

if if aint broke dont fix it
and spend the money on porn

[Plumba 54]

porn gets my vote as well.

[london calling]

Andy,Steve's right it is a big job as some of the lads racing in Forgotten Era and CRMC have done it.To do it properly requires mucho spark eroding and lots of machining.
It would be easier to start again with a complete uni-trak motor or put a uni-trak head on a J/GPz 17mm pin bottom end.I think there is a better availability of Wiseco pistons for the 17mm pin,but you'd need to check this.
It always costs money and usually much more than you think it will!!!!!!!!!

[Steve R]

Buy Porn,
You wont go as fast but you will come quicker!

[Guest]

Thanks Jack, i`ve just bought the head mainly in the hope i can use the shim under buckets in my existing head. Do you know if they are compatible? That way i can see how far i can go with different cams in the early head, then maybe use the GPZ one at a later date. I asked Brian Johnson about it today and he asked how high i was revving it, i said around 10,500, he said if you aren`t getting valve bounce you aren`t revving it enough! Oh and thanks for all the porn advice, i will use the money saved on modding the new head to help support the ailing porn industry, please give generously!
Also any more cyl head or cam choice advice is still appreciated, cheers.

[london calling]

Andy I would imagine that the buckets have the same diameter but i would check this out for yourself.Shim under bucket is the set-up to use.I bought a shedload of Z9/Z1000/J/GPz engines and bitz some years back that had been used for sidecar racing and most of the cylinder heads were totally knackered by having them spit a shim out at high revs.
A new shim under bucket set even with titanium retainers is cheap compared to the above!!!

[ADE]

Hi Andy i run a gpz1100 head on mine Mistral did the machining on the cam chain wheel.I run under bucket with 420 lift cams an a dash of nitrous for good measure.I have been meaning to get back on the road it is so close.I had everything re coated just need a back brake and mot.Must just be a lazy git or could i be waiting for the return of the LEADER

[Iain marshall]

Andy theres a wee bit about z1000 heads on the APE site,you might have seen it but heres the link http://www.aperaceparts.com/tech/techkz1000.html

heard that the Leader is back out in the next week or so

(Edited by Iain marshall at 8:38 pm on Oct. 10, 2006)

[Guest]

Hello Ade/Iain, thanks for that, i`ll check out that APE link later. I was talking to a guy at work today (who used to run a zed engined funny bike) about the GPZ head and buckets, he told me not to use the GPZ shim under buckets as the metal wasn`t compatible to the cams and would cause wear. He said he`d known a few people who`d done it and they always had problems, he said even if i use the GPZ head i`ll need to use APE buckets, bugger. Ade are you using GPZ or APE buckets, and do you think the GPZ head is worth doing? Oh and nice to hear from you again, i`m sure we spoke many years ago about Zed engines and your nitrous set up, get it sorted and ready for Santa Pod next year!
Another thing the guy at work said was to close the spark plug gap right up and it makes them rev harder! That`s a new one on me, i always thought you opened the gaps up to get a bigger spark/better performance not close them, still not sure if he`s winding me up.

[bunnysZ]

no wonder mikey gets lost all the time spending money on porn. he is going blind!

[ADE]

I use GPZ buckets i have heard that some people had problems with them dishing.I went for the GPZ route when i blew my motor clay cross were having a clearout and i got a brand new bare head for ?100 as the zed head was scrap.I supose the cost of new genuine buckets to APE would not be a great difference I also use orient expense valve springs and the cams are zed thou so they fit.Hope this helps.Its that slippery slope its like drugs you can have all the horsepower in the world but you still want more

[zed1015]

Hi. andy. Have done this same conversion to my own Wakisaki Z1R streetfighter earlier this year. It is no big deal fitting the head as it bolts straight on.You just need the APE idler wheel converter and the drilling jig + some minor milling done to square up the camchain tunnel in the head where the converter sits. I'm using an early 'J' type gpz head with hemi combustion chamber as opposed to your later ( bathtub) head and 10.25 1075 wiseco's but still running shim over buckets for ease of adjustment as these are safe until you get to using + 11000rpm and wild cam profiles (drag spec etc ).For the last 3 years before i did the conversion i was running an ex race z9 top end with shim over buckets and 11 to 1 ish yoshi pistons /engle race cams and 1mm o/s stainless valves which would regularly see 12000 rpm and never spat a shim ( Maybe i have been very lucky ? )As for the z/gpz buckets they are all interchangable but as mentioned in an earlier post the kwak shim under bucket material is not compatible with a lot of after market cams. Hope this is of help.

[Guest]

Hi zed1015/Ade/anyone else, thanks for the info, i spoke to Alan Jefferies today who seems like a really nice guy and knows his stuff. He said i would need to have the pistons machined to get the clearance as i have 13.5:1 domed pistons, it wouldn`t be a problem with standard or flat top pistons. Also i would need to use APE buckets and titanium retainers as the kawasaki buckets are not compatible with my cams as confirmed by zed1015, which could cause both to wear out and possible dishing of the buckets as Ade had heard. It sounds like a lot of work and money to be honest for i`m not sure how much gain. zed1015 why did you change from your old set up to the GPZ head? Did you gain much power and do you know the figures? Mine is currently 130bhp at the rear wheel. Also Ade, did you notice much difference in going to the GPZ head? I`m thinking now to keep the head for possible future use (or sell it if i get a good offer) and get my existing one converted to shim under and then fit the lairy cams, hmmm decisions decisions.....

[london calling]

I bet it's the same Alan Jefferies that worked at TTS back in the late 80's.He raced a Z funny bike,a turbo-charged and multi-staged nitorus monster.It was featued in Superbike magazine and there was a picture of Alan doing a full bore dyno run and stripping all the chrome off the exhaust manifold,it was RED HOT.
Iain Marshall might be able to post a picture off it for us to see as i'm sure it's in the folder of Z stuff i've lent him.