pozican

I had some pitting in my head, and they ended up taking off 20 thousenths.

Uhoh I thought to myself.

Is there going to be enough valve to piston clearance?

I know I'll have a higher comp ratio, so I'll be sure to turn down the boost a bit (I'm at 18psi)

I don't have a whole lot of money to be dumping in a new head, so I'm really worried.

Is there anything else I should be worried about?

Thanks guys!
-poz

jmporsche944

Thats standard I believe.. its never been resurfaced before though right?

pozican

Nope -- Never been resurfaced.

My NA head was only 4 thousandeths so I was a little worried


Thanks man!

Pauerman

Hey Pozi,

Here's what the manual says: if you machine enough material away to get dimension "A" between 23.6mm & 23.8mm you need to use the thicker 1.4mm head gasket. If your thickness measurement is between 23.9mm & 24.1mm you can use the standard 1.1mm gasket.

Even if you go under 23.6mm you can get a custom gasket from Cometic. They make 951 head gaskets in .005"-.010" increments in thickness that will go up to .120" thick.

Oddjob

20 Thousandths will be fine to use with a standard thickness head gasket. I have taken that same amount (which was recommended by a local p-car shop) off 3 different 944T heads, used a standard thickness WF-Ring headgasket on all them.

Shop owner did tell me that if you take off too much (40 thou. +), that you can run into problems not being able to tension the cam belt on cars with the manual tensioner. The auto tensioner has a greater range of adjustment, so it does not have the same limitation. I have not run into this problem myself, but have not shaved that much off any of the heads - so I have no reason to question his info.

toddk911

Worst case, you could just get a thicker headgasket.

DAR951

When you change the distance between the cam and the crank by milling the head, you also change the effective valve timing... If you don't go with a thicker gasket (which may also bring the distance back to spec) then you may want to think about either using an offset woodruff key or an adjustable cam gear to restore your cam timing.

ibkevin

No worries, ask me how I know...

Van

+1

eospeed

I would also say dont go back there for any work.I do my own an when I surfaceed my 951 head I took off .002 an it was perfect.Now if your head was warped thats another story.But sloppy machine shops will just whack .020 off a head an not think twice its such a waste an as stated above it will change the cam timing.

E

Oddjob

Taking 0.020" off is done on purpose, to get a slight gain in compression. It also is not enough to adversely affect cam timing, nor necessitate the need for adjustable cam gears or offset key.

Keep in mind, that rubber cam belts, made by various manufacturers, that stretch with age and loading, are not within 0.020" of the nominal spec. So how many guys check and adjust their cam timing based on slight variations in length of different cam belts - none.

pozican

That's not a problem, they are very competent. They took off what was needed to eliminate the pitting. Unfortunatly, there was still some left, even at .020.

On my NA they didn't take .020 off, because all that was needed to eliminate the warp was .004

Thanks for the concern though, it is what I asked for
-Alex

pozican

Good to know

Techno Duck

Just curious, do most cylinder heads removed from our cars need to be resurfaced due to some small but measurable warping? I had my cylidner (with about 85k miles on it) head checked at a machine shop and instructed them to do whatever was needed to make it perfect (new valve guides, 5 angle valve job and check for flatness). They told me the mating surface was perfectly flat and required no milling. I was surprised it didnt need any.

hosrom_951

Jon,
You need to ensure the head is flat and true, the cylinder head on my car did not require any. But i had the head decked by 0.096mm (less than 0.1mm) as added insurance.