att stuat v max and turbo dave
Turbo Mini Forums

hi im currently chambering out my own head at the moment.

ive got cylinder 1 to 31.5 cc and cyl 2 to 31.75cc

im going to make 2 and 3 .25 cc bigger trying to avoid detonation as it seems to be these two which will detonate first if it happens.

but what tolarance + /- cc do you work to when you chamber out you heads.

obviously i will try and get them spot on.

always looking for them bigger bunches of bannanas

I am also interested to the tolerance!
How much difference between the cylinders is negligible?
Or other question: How much difference in compression is negligible?

Edited by akirch on 12th Jan, 2005.

http://www.minifreunde.at

How are you measuring the volumes, are you using a pipette? If do you know where could get hold of one please? Thanks

Yes, Im getting there.....

www.itsmuckingfagic.com

i heard somewhere u can clamp a thick piece of perspex or similar across the chamber with a small hole in it. Through this hole u can fill the chamber with a low surface tension fluid via a accurate measuring device such as a pipette or a syringe.

Credit to you hogster, i couldnt bring myselft to take a grinding wheel to my heads!

Edited by Mike on 12th Jan, 2005.

Stuart is the head guy...

I've probably got the worst cylinder head on this site... Totally home-machined, over four years ago when I knew a lot less than I've since learnt!
I know my chambers vary by at least 0.2cc.
Once i'm set up in my shop, and looking to develop my engine further, i'll either be buying a head off Stuart, or modifying one myself...

As regards measuring them, the cheapest and easiest way is the perspex plate with two 5mm holes drilled in it (one to fill, the other to let air out). Then you buy a 25cc - or ideally a 50cc syringe from your local vet. Usually a couple of pence donation in the charity box on the front desk is adequate payment - at least it was in my two local vet's!

You can buy a burette for measuring. I've had two - and broken two! They are very fragile thin glass tubes! If you buy one, find a piece of plastic tube or something to keep it in...

Edited by turbodave16v on 12th Jan, 2005.

cheers for the replys guys.
TD im using a 5 cc syringe which i pinched of my daughters we used to use them for squirting down the calpol!!!!.

yep i use a piece of glass and plenty of vasoline and tilt the head at an angle in a big vice and do it that way seams ok and just leave a big enough gap to get the parifine in.

mind you its bloody hard work but in the end it should only cost me ?50 thats a set of guides and a skim to build it as i have allreadey got the valves p[lus a few stones for my router.

but im one for trying it yourself and see what happens as i have not got a lot to lose but all to gain.

plus save a quiet a few quid in the process, i no that a pro job from say stuart would be better but it is the achievement if it works buy doing it yourself.

Edited by turbo hogster on 12th Jan, 2005.

always looking for them bigger bunches of bannanas

sorry its all secret!
glass burrette 50 cc with ptfe tap(from medical supplies place in hastings ?23 wooden stand so you dont break it ?20) perpex sheet 5x5 in two holes (fluid in air out)stick to head with grease to seal
road heads +/- .5 cc, race +/- .1 cc
using a router will give a good result be carefull try to poke around with some wire/small allen keys to find out how thick it is , biggest i have ground was 39.5 cc, but i have holed a road atmo head at 23 cc , the castings vary a lot !!!
remember somtimes you find out its too thin when the engines running !

Edited by stuart gurr - vmaxscart on 12th Jan, 2005.

different compressions on each cylinder to
avoid pre ignition :
if its not too much boost, to hotter charge , octane too low -by oil mixing with it or otherwise- then its usually a hot spot igniting the fuel , check for :
gasket over hang
sharp edges to chamber or bore or valves or spark plugs or pistons
sometimes its not overcome buy lowering compression in the affected cylinder and if the water and oil have mixed previously flush the system as oil residue in the block or head can stop the heat transfer from iron to water