Xu7 Head Polishing,porting,upgrading,how To?

[pugpete1108 62 1 Cars]

My thoughts exactly, cheers.

 

I think I would have been much easier with the valve guides removed but hey ho

[calvinhorse 870]

Nice one

 

Watching with interest

[petert 586]

I think if it looks right then it most probably is.

 

I'm not sure that's applicable in the world of Reynolds. Good luck with the therapy anyway.

[pugpete1108 62 1 Cars]

right made alot of good progress on this, by the third pair ive got pretty good at it too so much so i think i will go back over the other two when im done.

 

still got a small crease in the casting just below the seat which i cant seem to get out as i dont want to damage the seat itself.

 

 

only thing i have just noticed (cant believe i didnt see it sooner) was a small amount of damage to the face of the head right by the fire ring on the inlet where the metal is really thin. do you think i will get away with this? or will it need welding before skimming?

 

[DamirGTI 342]

Nice .. port throats are nice opened , just do not "polish" the surface - finish inlet ports with 80grt .. cos they need to be little "rough" , exhaust ones - can do them mirror finish if you like cos there it doesn't matter the more fine surface on the exhaust ports the better ...

 

Valve guides protrusion inside the throat - really doesn't effect on port flow measurements , so no need to bother with them .

 

Next , do the combustion chambers - as the exhaust , make them fine mirror finish surface .

 

D

[pugpete1108 62 1 Cars]

Best I've got to hand is 120grit is that too fine?

 

You think the damage will be ok?

[DamirGTI 342]

It'll do but the 80grt. on inlet is always best .. the worse thing that you can make is , to do it blink shiny port surface on inlets - this'll upset the "swirl effect" and AFR ratio , cos fuel molecules needs a little rough surface to "bounce" around the port insides in order to be broken in smaller molecules evenly mixed with air molecules for better and more complete burning of the air/fuel mixture , with a minimum left unburnt molecules on the end of the combustion process which , if there's a lot left inside the cylinders it'll upset every second combustion cos there will always be left XY proportion of unburnt air/fuel molecules within the cylinder after the end of the previous combustion cycle .. there's a lot further downsides with regards to igniting such mixture , possibility for detonation etc. but don't want to bother you about the lot ..

 

Just clean up the casting imperfections and , seriously don't bother with making inlet port finish nice shiny .. i rather left them as OE just clean up the ports .. oh , and , do not by any chance grind the floor (down side) of the ports inlet and exhaust included - only place where you can use grinder on the ports is roof (top radius side) .. you can raise it up a bit if you want on both the inlet and exhaust .. this will assist "swirl effect" , but without of aid of the flow-bench , it's a little bit tricky so best left OE just place the inlet gasket on the head and just grind off excess area between the gasket inner ends with relations to the inlet port entry's (again , just sideways and top , don't touch the bottom even if you see that theres some excess "meat" between the down side of the ports with relations to the gasket ..)

 

Exhaust ports , also clean up the castings imperfection and this you better of getting it a little smother , so that the gasses can slide/escape more quickly from the cylinders out ..

 

As for the crack - place (if you gave ..) old head gasket and again , see if there's free space between the combustion chamber and head gasket fire rings , usually there's always as minimum 2mm. surface which you can make radiused around the each valves , it's called "valves unshrouding" .. so yes grind that crack away , but make an radius .. the rest will clear once you done the head and skim the head base .

 

D

Edited March 23, 2013 by DamirGTI

[pugpete1108 62 1 Cars]

Bit late with the bottom if the ports as I've pretty much already worked then, not too much though in comparison to the roof .

 

I've basically just smoothed out the casting on the inlet top and bottom and levelled them out to the size of the gasket.

 

I've opened above the valve to just bigger than the seat and opened it right up through the Siamese and the throat around the valve.

 

It's still fairly rough after the 120 so I'm going to go with that.

 

So I can go back as far as the rings all round the chamber?

[petert 586]

If the crack is inside the gasket it should definitely be removed. Do a search of "unshrouded inlet valve" on Google images. You'll soon get the idea.

[gnw 0]

i did modified my xu7 cylinder head

i didn't removed ALL the restriction on the valve top, because, it's not exactly the BEST thing... obviously, better then the original... that happens that the biggest restriction appears suddenly, between the valve and the valve seat. the air must be slowly restricted ... except on turbo cars, that largest is better...


i removed just one side of the triangle, and the inlet port, i did the same size as the inlet manifold. i'm using a GTI manifold

 

 

[pugpete1108 62 1 Cars]

i opened mine up all the way around.

 

somewhere in between the xu10j4rs head (which has massive ports) and the xu7 head.

 

 

[gnw 0]

behind the valve seats, i think you're opening too much!

that creates a big obstruction, between the valve and the valve seats.

the restriction must happens continuously! and not suddenly, like happens, when you have a large duct.

a good thing to do is make angles on the valve. at least two...

i did 30 and 45º on mine...

it reduces the obstruction between the valve and the valve seats, and makes all the diference...

[pugpete1108 62 1 Cars]

Why does the gti6 head generate so much more power then?

 

Given its much more open the mine?

 

I guess the proof is in the pudding, and we'll see what power it makes on the rollers.

[welshpug 1,657]

its not just the head, its the combination of parts, i.e both manifolds, cams, extra compression, minimal difference in valve sizes but it all adds up.

[gnw 0]

its not just the head, its the combination of parts, i.e both manifolds, cams, extra compression, minimal difference in valve sizes but it all adds up.

 

 

 

exact...

[pugpete1108 62 1 Cars]

Ok, so if I was to get a gti6 head,cams,manifold etc and restrict the ports it would be better?

[welshpug 1,657]

how would you "restrict" the ports? i.e add material?

[pugpete1108 62 1 Cars]

You wouldn't, I'm just trying to make a point that opening the port to not even the extent of the gti6 head can't be 'bad'

[DamirGTI 342]

.. enlarging the port is kinda bad idea , smaller round ports will flow better for NA .

 

But as said , it all adds up to which combination of part modification you've planed for particular cylinder head .

 

D

[pugpete1108 62 1 Cars]

Ok well hopefully I've not gone too far then

[calvinhorse 870]

I've just put a gti6 inlet and exhaust on a otherwise standard 1.8 16v and it's made a huge difference to the power, it revs alot more freely but definately needs gti6 cams!

 

I'm going to be using a 2.0 xsi head with gti6 cams as soon as I find the time!

[pugpete1108 62 1 Cars]

I've just put a gti6 inlet and exhaust on a otherwise standard 1.8 16v and it's made a huge difference to the power, it revs alot more freely but definately needs gti6 cams!

 

I'm going to be using a 2.0 xsi head with gti6 cams as soon as I find the time!

sounds encouraging

[petert 586]

I'm going to be using a 2.0 xsi head with gti6 cams as soon as I find the time!

Beware of spring bind. There's a reason why RS heads have double springs.

[calvinhorse 870]

Beware of spring bind. There's a reason why RS heads have double springs.

Sorry should have mentioned that!

The 1.8 valve springs are comically soft.

[gnw 0]

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