1.9 Head Skim

[paulfreeth 0]

Hi all, just trying to find out how much i can have skimed off a standard 1.9 head. The engine is totaly standard im only taking the head off due to a snapped exhaust manifold stud, but well its off thought i would regrind the valves, reshim the valve clearances, and get the head skimed to get a bit more performance.

Any help will be much apperciated

[wardy18 33 1 Cars]

hi mate

 

See the link here:

 

Head Height Measurments

 

This will enable you to measure your head height using the diagram showing where to measure between then compare it to the stated base measurements on the page, this will tell you how much has already been skimmed from your head in the past from rebuilds etc.

 

The most you can safely skim from the 8v XU9 head is 60thou (0.060" or 1.524mm), this will take you up to approx 10.9:1CR on the std D6b pistons!! Ignition timing will also need advancing to get teh full potential!!

 

I already have a head with this done and 3 angle seats sat going to waste, all yours if you make any use of it?! PM me

 

Rgds

 

Simon

[petert 554]

I thought 2mm was the safe limit. I've certainly taken that much without any problems. You wouldn't be wise to take that much however. I'd say 1mm, to get you just over 10:1. Then don't forget you'll need to advance the cam timing, to make up for the skim distance.

[paulfreeth 0]

I thought 2mm was the safe limit. I've certainly taken that much without any problems. You wouldn't be wise to take that much however. I'd say 1mm, to get you just over 10:1. Then don't forget you'll need to advance the cam timing, to make up for the skim distance.

Thanks for your reply. How would i go about advancing the cam timming, do i just put it out a tooth? Not sure what im doing yet as i took the head off tonight and the liners are twisted slightly, and the pistons seem to have alot of movement in them, altough the car never smoked much (only when cold) and seemed to go like stink.

[petert 554]

How would i go about advancing the cam timming,

 

You need to either fit a vernier pulley or find a decent machinist/tuner who knows how to modify the standard pulley. A 1mm skim equates to approx. 4 degrees. ie the cam will need advancing 4 degrees. Try Miles or QEP.

[paulfreeth 0]

Thanks for the advice.

Think im going to get 1mm taken off (providing it hasent already been skimed) and fit a vernier to adjust the cam timing to suit.

[cRaig 265 1 Cars]

Out of curiousity, what happens if you dont adjust the cam timing?

[RalliArt 0]

hi mate

 

See the link here:

 

Head Height Measurments

 

This will enable you to measure your head height using the diagram showing where to measure between then compare it to the stated base measurements on the page, this will tell you how much has already been skimmed from your head in the past from rebuilds etc.

 

The most you can safely skim from the 8v XU9 head is 60thou (0.060" or 1.524mm), this will take you up to approx 10.9:1CR on the std D6b pistons!! Ignition timing will also need advancing to get teh full potential!!

 

I already have a head with this done and 3 angle seats sat going to waste, all yours if you make any use of it?! PM me

 

Rgds

 

Simon

So, you say 10.9:1 CR with the D6B pistons, tell me if I'm wrong but aren't they(the pistons) the type with the larger volume chamber of the piston, or the type of with the smaller cc chamber(like 1.6gti engines)... I'm asking because I'm preparing a similar head from d6b engine, mine is a stock 1.6, and I'm wondering what will become the CR if i skim 1.2mm the head and giving the proper advance of the cam witch i suppose is about 5 degrees, so skimming it 1.2mm won't be fatal is that correct ?

And can you tell me what will be the proper ignition timing?

[paulfreeth 0]

Out of curiousity, what happens if you dont adjust the cam timing?

 

I think to adjust the cam timing properly you not only need an adjustible cam pulley, but you also need to use a dial gauge to know exactly where to set the verneir pulley. Ive been told that to gain the maximum benifits of having a big skim on the head this is the proper way to go.

[cRaig 265 1 Cars]

Okay.. I see how you do it now, but maybe im being stupid and missing an obivous point.. but why do you have to do it? What does it achieve, and what happens if you dont?

 

Sorry, im not trying to be pedantic, Im just trying to get my head around it

 

Craig

[petert 554]

Because any gains picked up by an increase in CR will be lost through retarded cam timing.

[paulfreeth 0]

Has anyone had any experiance at adjusting cam timing properly? sounds like a complicated time consuming job, but not somthing to ignore.