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can you shave stock head?
Posted: Wed Jul 31, 2013 1:49 pm
by 16bit
is it possible to simply shave the stock head to bump it up from 9.5 to 10 comp ratio?
by that i mean take the stock head off, shave it and put it back on?
more of a theory thing that actually thinking about doing it.
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 1:57 pm
by hks_kansei
Can't see any reason you can't.
Depending of course on things like piston/valve clearance, and how it effects the water/oil galleries.
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 1:59 pm
by NitroDann
We just did PaulFs head from 9:1 to over 10.
It flies
Dann
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 2:16 pm
by 16bit
did you crack open the head at all Dann? or just shave it and put it back on?
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 3:07 pm
by NitroDann
Pulled it apart as cleaned the lifters and ported it.
Stock hardware though.
made a VERY good difference with almost no money spent.
Dann
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 3:08 pm
by 16bit
sweet, this is tempting.
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 3:15 pm
by 16bit
how much did you shave off?
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 3:25 pm
by NitroDann
Lots, like 27 passes. So 27 thou I think.
Shaved it until the valves were even with the surface.
Dann
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 3:25 pm
by NitroDann
Might have been 2 thou per pass.
Dann
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 3:30 pm
by 16bit
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 4:19 pm
by NitroDann
27x2 is 54 thou, which I think is correct.
Ill confirm.
Dann
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 8:57 pm
by Mr Morlock
machining heads has been done for ever but you must take proper advice on what to remove. Its also wise to actually work out what you expect to achieve and what are the risks in doing it. There is a $ cost in doing it and a $ cost running it because an increase in the compression ratio may result in the need for 98 fuel. Longevity may be affected. You may need a new headgasket etc. Paying for the work to be done - which most people do- is going to cost more than one might imagine
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 9:12 pm
by NitroDann
I confirmed it, pauls was aiming for 50 thou (1mm) but couldnt do it without removing the valves so stopped at 48 thou.
Then we removed the valves and ported it lol.
Dann
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 9:50 pm
by noobee
48 thou(inches) is close to 1.2 mm.given a stock engine with 9.4CR and stock head gasket,your new compression ratio should be somewhere around 10.7CR.you cleaned up any sharp edges/hotspots in combustion chamber when porting I assume.
Mick
Re: can you shave stock head?
Posted: Wed Jul 31, 2013 10:01 pm
by NitroDann
Yes we cleaned it up and smoothed the edges.
Is it really?
Wow, thats a lot, I thought it was 10.3 ish, I never sat down and did the calcs just asked the advice.
Dann