Difference between GT head and G40 head

[Jake G 4 0]

Hi guys,

Just after some info, is there any difference between a G40 head and a GT head??  I'm guessing there is but if not could I fit one on my G40 ??

Thanks for any input.

Jake

[PeteG40]

difference is the valves.  castings are they same.

so if you get your g40 valves ground/cut in to the gt head - it'll be a g40 head

[samg40]

Those and the cam of course.

[Jake G 4 0]

Sweet thanks pete. I'm just in the middle of a rebuild and found cracks on each valve seating some are tiny but one is huge .

So it shouldn't be too much hassle getting a gt head and turning it into a G40 as long as I use my cam aswell

[samg40]

Cracks are common there. Have you got any picutres to put up? Mine's been fine.

[Jake G 4 0]

So your saying you have got cracks in your head but it's still fine?!?

Ill get some pictures as soon as i can as my car isnt at mine so i'll have to get them later or tomorrow

[PeteG40]

get your machine shop to pressure test it.. most polo 8v heads have cracks of some sort

apparently golf 16v kr heads crack on first fire up from the factory!

[hayesey]

Pretty rare to find a head that hasn't got hairline cracks between the valve seat and spark plug holes.  Same on golf heads too.

If one is big though then that's a problem, can you put some pics up?

Any 1272cc polo head is the same casting and can be used with the right valves and cam fitted.  Doesnthave to have come from a gt or g40.

[Jake G 4 0]

Here are a few pics, the one with my finger is just for a size guide.

What do you think?? There are two cracks on the one set one inbetween the inlet and exhuast valve and one on the spark plug. All the others have one hair line crack

[Jake G 4 0]

on the same set of valves

[Jake G 4 0]

second set

[Jake G 4 0]

third

[Jake G 4 0]

size

[Yoof]

Nice crack 

Most heads (mine included) have cracked in this fashion, unless it's burning coolant then there's little to worry about, providing the cracks aren't large enough to release the valve seat.

When getting it pressure tested, get the combustion side (not coolant) tested, not many places will do this as it's quite high pressure (should test at over 50bar) this will tell you for sure if you've got any crack related leaks.

[Jake G 4 0]

Cheers yoof

My G used to lose a little coolant before but I put this down to a leaky rad so I used a bit of cheeky rad weld to see if this was the problem and it seemed to stop losing coolant, so I don't think it was loosing it through the crack.

I also had it pressure tested before it all came apart because I thought the head gasket has started to go, they found products of combustion somewhere could this be from these cracks??

Also I would have to bolt it all together just to have it tested again right? So it maybe easier to just source another head?? Because I need new valve guides in this hea anyway.

Cheers jake
Ps sorry about all the questions