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Discussion Starter #1
I've heard a few people mentioning about skimming a head, but I don't know exactly what this process involves. At a guess, i'm thinking it literally means skimming the head, i.e. shortening the depth (can't think of another way to put it, but you get what i mean). If this is the case, does it increase power by increasing the compression ratio? I've also been told that by doing it to my 1.8 Ecotec it should give me the same power as a 2.0 Ecotec, is this true? And finally, is it safe to do this, I mean would the lifetime of the engine be likely to be any shorter for example.
Thanks.
 

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same power no

but it will increase the compression ratio which may give a slight increase in power although not a great amount, shouldnt affect the lifespan of the engine in any way shape or form as long as you keep it within tolerances


best thing to do is get a skim done(i presume your in the middle of a headgasket change) as a matter of course and give the head a basix port and polish match your inlets and exhausts to the manifolds plenty of guides kicking around just remember keep it sensible and do go overboard
 

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imo there are far far better ways of increasing the power of an engine than increasing compression ratio (which is what skimming is doing)

if the heads off, headwork is power for free, with no detriment whatsoever (for a road spec head anyway) - unlike skimming a lot off, which increases the risk of detonation etc, not to mention reduces the timing clearances.

high CR should be the last thing a tuned engine needs - and you won't gain 20bhp (i.e X20 performance) from it either, no way.
 

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Discussion Starter #4
Ah ok, cheers. The engine is all intact at the moment, headgasket was replace recently but before I bought the car. What sort of mods should I be looking at to get some decent power increases, but not too expensive lol. I am hoping to do a C20XE transplant at some point, but for now it will have to stay as it is.
 

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You are correct in your understanding of skimming a head. People seem to claim some magical properties from skimming a head. Running high compression ratios is a waste of time on std pump fuels. It does not give much of power increase and it shortens engine life.
 

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the 1.8 ecotec is rather ignored tbh, so apart from the usual exhaust/inlet optimisation for a couple bhp, you'll have to open the engine up - headwork is the best start I guess.

best thing is wait for a transplant tbh, otherwise whatever you do is dead money.

I'll be having the head off my X18XE in the next couple months to repair a stud - but will also work it (I know someone who does em, lol), be interesting to see how well it responds.
 

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yeah, skimming is an old school mod that worked great on certain old engines - but it really is questionable at best on the modern stuff.

2 or 3 skim thou to ensure flatness, and keep plenty of future life in the head imo.
 

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Gary said:
imo there are far far better ways of increasing the power of an engine than increasing compression ratio (which is what skimming is doing)

if the heads off, headwork is power for free, with no detriment whatsoever (for a road spec head anyway) - unlike skimming a lot off, which increases the risk of detonation etc, not to mention reduces the timing clearances.

high CR should be the last thing a tuned engine needs - and you won't gain 20bhp (i.e X20 performance) from it either, no way.

:rolleyes: in that case, can i have my money back lmao
 

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Gary said:
yeah, skimming is an old school mod that worked great on certain old engines - but it really is questionable at best on the modern stuff.

2 or 3 skim thou to ensure flatness, and keep plenty of future life in the head imo.
Correct
 

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Dont know what these girls are talking about but skimming the head does have a pretty good effect on performance (depending how much you skim off)! for example jumping from 9:2 to 11:0 would be a worth while investment, the smaller the chamber the better the cumbustion!
 

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skimming a head to increase cr will normally increase the power you get from an engine, but only if the timing is still safe, the gains are minimal though.
higher cr also increases economy too.
higher cr will lower the number of miles the ringseal and valve seal last
 
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