172 head skim

[mgoode180566]

Can a 172 cylinder head be skimmed ? What is the maximum that can be taken off it ?

 

[Cristi_Xp]

if you want to increase your CR , you should use high compression pistons , not skimming the head .

 

[mark123]

This thread reckons you can skim 1mm off the head.

http://www.cliosport.net/forum/showthread.php?195585-Compression-12-6-1/

 

[Dan519]

if you go too far (more than about 0.4mm) you'll have issues with the cambelt tensioner not having enough adjustment to tension the belt.

 

[cliobritt]

Do you need to take cams ect out to get a head skim?

 

[mx1_champ]

Do you need to take cams ect out to get a head skim?

fully stripe the head back to nothing

 

[Alastair.]

Not supposed to skim these heads f4r, k4m, k4j etc etc. Renault say its a no no.

 

[cliobritt]

fully stripe the head back to nothing

So you can't skim otherwise?

 

[mx1_champ]

So you can't skim otherwise?

you probably could still have the skim done.. but then what you going to do with a head full of swarf ? and i highly doubt anywere will perform a skim with a built head..

only takes half hour to strip a head anyyway.. if that. then atleast you can renew all the seals etc while your at it

 

[Dan519]

Do you need to take cams ect out to get a head skim?

you can't remove the head without removing the rocker cover anyway

You can leave the valves in

 

[Dan519]

Not supposed to skim these heads f4r, k4m, k4j etc etc. Renault say its a no no.

only issue is with standard map and detonation from increased compression. You can skim the head perfectly safely as long as you address this.

 

[bozothenutter]

on a side note.....what would the torque/power increase on a 738 be with a compression of about 12.5:1
it's a roadcar, but running on 98 all the time.
will it need rehoning and such?

 

[Cristi_Xp]

no , only skimming the head, and adjusting the ignition and fuelling maps so it won`t knock and overheat the engine .

 

[bozothenutter]

so with new pistons a rehone is not neccesary?
A remap is ofcourse part of the plan....

 

[Dan519]

so with new pistons a rehone is not neccesary?
A remap is ofcourse part of the plan....

this is not the same question, of course with new pistons you will replace the rings, so a hone is important. This however has nothing to do with skimming the head

 

[bozothenutter]

my bad, the question wasn't cencerning skinning the head, but was about increasing compression in general.

 

[TheEvilGiraffe]

Can a 172 cylinder head be skimmed ? What is the maximum that can be taken off it ?

Surely the first question is - why do you want to / need to skim the head ?

 

[mgoode180566]

Suspected headgasket failure. Want to know if the head can be skimmed and what is the tolerance...

Surely the first question is - why do you want to / need to skim the head ?

 

[Cristi_Xp]

this is not the same question, of course with new pistons you will replace the rings, so a hone is important. This however has nothing to do with skimming the head

if there is not use on the cyllinders , so the bore size remains as stock,and you order pistons with stock bore , will it still need a rehone ?

 

[Fred@BTM]

Suspected headgasket failure. Want to know if the head can be skimmed and what is the tolerance...

very very very very very very rare! symptoms?

 

[mgoode180566]

compressions ..... zero zero 80 155............

 

[Laine_16v]

Sounds like the timing has somehow slipped and bent some valves, but no outright belt snap. Wouldnt be a HGF in my opinion.

Had the belts been replaced recently?

 

[Tony Hunter]

compressions ..... zero zero 80 155............

Thats not good,even I know that.

 

[Dan519]

compressions ..... zero zero 80 155............

Ouch. Really ouch. I think laine could be correct. Unusual for by to go except in extreme circumstances

 

[mgoode180566]

if belt slipped it would be instantaneous. The engine light came on twice five mins before hand then cleared. Wouldnt this indicate something confusing the exhaust sensors ? Belts has been on for 60k.... The luck i have had this year you wouldnt believe. The year from hell.....

 

[Dan519]

lost a lot of coolant? only times I've seen these do a hg was from a massive overheat (block was blue!!!) or headbolts not tight enough

 

[Will.]

What does head skiming do

 

[Dan519]

the primary objective is to give a flat sealing face. A secondary benefit and something often taken advantage of, is by removing more than the minimum necessary (standard practice) you can raise compression by reducing the size of the combustion chamber

 

[Will.]

Oh ok that makes sense

 

[mgoode180566]

it did blurt its coolant weeks ago and i refilled. of course it went for a reason.... going to pull the motor and see what i can find.