Cylinder head and gasket??

[Bart GTI-R]

Hi all , currently taking the engine out and in the process getting everything ready to fit, already got a head waiting to go on thats been skimmed and had all the valves lapped etc.. and shims set up, but because Iv had the head skimmed will I need a thicker head gasket or adjustable cam sprockets as Iv been reading a few posts about once the head has been skimmed it can affect the timing?? im not to sure on this and before I build it back up just want to be sure of everything.

Thanks in advance for comments and advice.

 

[pulsarboby]

you wont need adjustable cam sprockets.
and it will not hurt if you upped it to a 1.4mm jobbie to compensate for the head skim or even 1.6mm.

 

[Odin]

I had to have adjustable cam sprockets fitted to allow the cams to be dial-ed in correctly because of the head and block skim, They also fitted a 2mm head gasket to give me the correct comp ratio.


Rob

 

[pulsarboby]

you dont need adjustable sprockets rob, as the tensioner will just take up the excess play in the chain. but if your going as far as you have gone with your build then its a different story, as youll get better manual timing with the adjustable sprockets (if there setup correctly)
but for a normal head skim and rebuild there by no means a must have item. as you are replacing the skimmed metal with an equal gasket

as for the head, well it all depends as to what the skim is that you have had!!! if they have skimmed the head and block face then yes i would say a 2.0mm gasket is a must. but if just a head skim then 1.4 to 1.6 should be more than sufficient

 

[Odin]

Don't forget if you don't get the new gasket size spot on then you will need to have the oil pump housing skimmed to match the head as well.

As far as the sprockets go, I was advised that it was essential in my case.




Rob

 

[GINGA]

You would ideally need adjustable pulleys if you have had the block or head skimmed or fitted a larger than std head gasket as the distance between the cam pulley and crank pulley is now different so the timing will have changed. The tensioner only keeps the tension on the slack side of the chain.

 

[GINGA]

Don't forget if you don't get the new gasket size spot on then you will need to have the oil pump housing skimmed to match the head as well.

As far as the sprockets go, I was advised that it was essential in my case.




Rob

You only need the oil pump skimmed if you have the block skimmed, ideally you would have the oil pump bolted to the block when it went for skimming.

 

[pulsarboby]

You would ideally need adjustable pulleys if you have had the block or head skimmed or fitted a larger than std head gasket as the distance between the cam pulley and crank pulley is now different so the timing will have changed. The tensioner only keeps the tension on the slack side of the chain.

true unless you compensate for the skim with a head gasket to suit, then no distance has changed and valve timing and cam duration will remain the same as before skim.

in robs case then it was necessary due to the way hes engines been built and the volume of work he has had done. but in a normal head skim you would just make the difference up with a gasket to suit.

 

[jpward]

Sorry to hijack but how bad would the surface be to warrant a skim or say under what circumstance is it absolutely necessary?

 

[Keira]

cam duration

how does taking metal off the head or block affect the duration of the cam then ?

 

[Odin]

how does taking metal off the head or block affect the duration of the cam then ?

What he means (I think) is that when you skim X amount of the head and block, That can't be compensated for by the correct head gasket, Then the chain timing marks would then not line up as they would normally do, So you would need the adjustable cam sprockets to compensate for this discrepancy ;-) .

This was the case when they built my engine.




Rob

 

[pulsarboby]

correct robbie, as the lengh of chain on the non tensioned side would be too long, hence altering the timing

as you say kieron it wont actually alter the duration of the cams, just me using the wrong terminology:der: but as above is what i meant and should have said:-D

 

[Bart GTI-R]

Thanks for all the replies guys, Iv got a better understanding after reading the posts, will get new headgasket to suit after getting in touch with the guy who's doing my head.

Nice to be part of such a helpfull club

Top Notch fellas

 

[Odin]

Nice to be part of such a helpfull club

Top Notch fellas

:shock: We don't hear that very often :lol: :lol: :lol: :lol: :lol: :lol: .




Rob