The 27.5cc chamber volume suggest the head may have been skimmed in a previous life. Pretty sure they are around the 30cc mark as standard. Did you measure the current head depth?
Yeah i reckon it's been skimmed, I think it was around the 137mm mark so not much more than the minimum recommended deck height. I'm not too fussed about that anyway as i was always going to have to skim more than that off to get the compression up to something reasonable.
Good lad. I took a couple of mm off the block on mine. You may need a vernier to time in the cam correctly after such a large skim. But just think of the weight saving.
Yeah I've been looking for one for a while but they seem to get snapped up pretty quickly on ebay. It'll need setting up on a rolling road at some point cos i imagine even my shoddy attempts at porting may have increased flow a touch. Well fingers crossed anyway
I've run the heads down to 21cc, but that's on the limit..24cc is more comfortable, and anything above is obviously fine.
sorry for late posting but i was interessted what head height should be to get something arround 24cc cheers
It's ok, it went to a good home. Was fooking rapid for what it was as well. Then I tried more valves and it wasn't
1.6 driver how much to skim? hello I'm doing complete head rebuild on my 1.6 driver and i want to know which head height should it be to get some reasonable CR arround 10:1 or more?
about 1.5mm Or you could source a higher compression block instead for less money - see the classifieds
so what would be final head height i ask beacose i dont know if it's been skimed before and i doesnt have tools to check cc of chamber
There should be a spec for the head height in the Haynes manual. 1.5mm is a rough guide. Really the best way to be sure is to measure the CC of the head (should be around 30cc), the dish in the top of the piston (not sure on a 1600) and allow for the thickness of the gasket (about 5-7cc) to work out what you need to remove to get the right CR. You don't need fancy tools to CC a head. Just a piece of perspex with a hole in it, some grease to seal up the holes and some light oil, and a syringe with ML marked on it. It won't be super accurate, but it'll be close enough.
haynes says that minimal head height should be 132mm and now this head has 131mm working perfectly gues i would have to find those things and measure height no other way to be sure 100% do you know how much cc will it need to get compression arround 10:1 or 10,5:1 how do you calculate CR based on cc of the chamber on head? cheers Nuki
depending on what your budget is id get a 2.0 agg block then gasflow ur head with gti cam or 295 piper cam and run a weber or twin 40s but twin 40s are alot of money not also is the inlet manifold i was lucky i got mine cheep and had them set up for 120 and dyno at 149.9 bhp/159.9 touqe. was rappid and sounded awsome. but now moved on to bike carbs and crossflow head. not evry one like twin 40s or the bikecarb route but it does make the 8v so much more fun that the 16v XD 8v FTW
Threads merged. Compression ratio is calculated by: swept volume + clearance volume then divided by clearance volume. 1595cc engine has 4 cylinders, making each cylinder 398.75cc ie the swept volume. So by doing some calculations you can work out that to get 10.5 to 1 you need a total clearance volume of 42cc. 398.75 + 42 = 440.75 divided by 42 = 10.49. For 10 to 1 the clearance volume would be 44cc. This clearance volume is the total volume above the piston at TDC, this is made up of piston dish, gasket thickness and volume of combustion chamber in the head.
Come on, I was rubbish at maths and arithmetic at school, but when I found an area of interest that I had to use these skills it makes it easier to learn them as you want to. So earlier in the thread I posted this. So get the calculator out and see if you can work out the volumes. Clues are the std compression is nearer 8.2:1 than the stated 9:1. And the standard head volume is approx 30ccs. Get button pushing and see if you can work out the answer to your question. I will open a bottle of red wine and correct the exam results as and when they are posted.
See, you have managed it. So now you know this figure if you just CC out your head combustion chamber volume you can add that volume to this other figure and see what you have, then calculate how much you need to lose to raise the compression to where you want it. This gives an approximate figure to work to. I usually dry build the engine to final check and gain a more accurate idea of exactly what I have.
thx i now understand what are you mean but still how can i then know how much to skim to lose that cc that is not needed or it is just try then measure again cc and so on until satisfied
