Skimming, How Far Can I Go?

[johnrobertgordon 0]

Sending an 8v xu head off for skimming, the head has been lightly ported and polished. The cam that is to be used seems to be 0.5mm bigger than a standard 1900 cam.

What is the max i can skim this head, its not been skimmed before. I have been told its 20thou but was wondering if i can raise the comp a little bit more?

 

John

[petert 555]

up to 2mm, but don't forget to modify the engine mount to suit.

[johnrobertgordon 0]

modify the engine mount?

[Greenys_meanies 0]

you could 'deck' the block too

[Rob_the_Sparky 9]

modify the engine mount?

 

The engine mount has 2 bolts into the block and one into the head. When you skim the head you move the centre of the bolt into the head down towards the block, hence the engine mount has to be machined to fit. I discovered this the hard way when trying to assemble the car!

 

Rob

[Guest ashnicholls]

fcuk! so what do you do about it, i bet mine wont line up, putting a skimmed XU10 head on my XU5.

 

 

 

iv skimmed the xu10 a fair bit, got 9.6~10:1 compression.

[Guest ashnicholls]

im waiting the mounting bolts, but just tried it with some threaded rod, so should be ok, if not do you just open up the holes in the mount?????

 

cheers

[Rob_the_Sparky 9]

Yeah, I tried by hand but there was too much material to take out so took it round to a local machine shop to slot it in the right direction.

 

Rob

 

P.S. I'm running 10.4:1 on an 8v.

[24seven 104]

Sorry to bring up an old thread, but am I likely to have trouble with the engine mounts after a 25thou skim? All standard components inside. Is it likely I may need to run 97 octane fuel to avoid pinking with this? Or is that for silly skimmed engines only?

[Rob_the_Sparky 9]

Not sure but you may get away with that but be careful to check when you are putting it together. I've seen a cylinder head break this mounting and I have a theory...

 

If you put the mount on tight and then torque down the head then if the mount doesn't have enough slack then you will apply the cylinder head torque side ways to this bolt putting a huge stress on it. Bear in mind though this is only a theory.

 

I have over 50 skimmed off mine though so you may be OK with 25 but just be careful to check.

 

Rob

 

P.S. on a 1.9 you should be running 97+ octane fuel anyway to get the performance from the engine, if it is 1.6 then I'm not sure.

[24seven 104]

it's a 1.6 .