Xu7 Head Polishing,porting,upgrading,how To?

[pugpete1108 62 1 Cars]

went to check on the car today, found oil in the damn header tank again

 

so it turns out it was not the bottom end that was the issue it was the top end, good news is i have an xu7 here which is good along with the bottom end.

 

so basically i have a complete xu7 engine of which i will be using the bottom end and head casting (with some porting) along with the gti6 cams and pulleys, inlet and exhaust mani and....... anything else? what valves/springs etc to use?

 

with regards to opening the inlets up, how do i go about it?

 

id guess buy starting with matching the port with the manifold but do i need to follow through down the inlet?

 

i havent got the time or the money to have it done professionally and tbh would like to have a bash myself.

 

i assume the exhaust ports are ok to leave as is? (i'll compare when i remove the gti6 head again)

 

any input would be appreciated

 

cheers

[Carbs4me 45]

I wouldnt bother porting the head, Pug did a great job of it really, If you get it wrong you will lose more power than you gain

 

As my mates says to me port and polish is just a money making scheme that does nothing.

[pugpete1108 62 1 Cars]

From what I've read it's the contrary to this with the xu7 head as its nigh on the same as the gti6 head but with smaller ports so can't see how not matching them at least will make similar power with the 6 cams etc.

[welshpug 1,657]

I wouldnt bother porting the head, Pug did a great job of it really, If you get it wrong you will lose more power than you gain

 

As my mates says to me port and polish is just a money making scheme that does nothing.

 

facepalm.

 

Whist that may be correct for most amateurs and XU9J4 10J4 J4R and RS heads, I suggest you read up on the XU7J4.

 

http://forum.205gtidrivers.com/index.php?showtopic=74214&page=1

 

http://forum.205gtidrivers.com/index.php?showtopic=84170

 

http://forum.205gtidrivers.com/index.php?showtopic=109748&page=2

 

I remember Sandy posting a diagram of the inlet ports showing the diameters of a few different XU 16v heads, XU7 was significantly smaller.

[pugpete1108 62 1 Cars]

nice bit of reading there,cheers.

 

not very clear on how to do it but it clearly shows there is a good reason to do it.

 

will probably start with just opening up the inlets to match the manifold and go from there.

 

chuck the 6 cams and manifolds on and see how it goes.

[pugpete1108 62 1 Cars]

right so i thought i would compare how much difference there is between the ports on the xu10 inlet and the xu7 head.

 

i made a tracing of the inlet ports on the manifold and compared them to the head. Oddly they are actually the exact same size? they look like they taper off slightly thiner (wont know for sure until i compare the actual heads). it deffo has not had any work done as you can still see the casting marks and texture.

 

 

 

[welshpug 1,657]

the main difference is further down the throat of the port, I havent found that cross section that Sandy posted a while ago, maybe worth dropping him a PM.

 

You do need to use the double springs, valve stem seals, lower seat and top spring retainer with the rfs cams afaik.

[pugpete1108 62 1 Cars]

yeah i have had a good search but didnt come up with anything. ive also pm'd him so will see what happens with regards to him carrying out some work

 

does the gti6 head have all the mentioned bits? why would i need to change the stem seals if not using the gti6 valves? i assumed i could just swap over the cams and badda bing done.

 

forgive me but im slightly behind when it comes to engine internals

Edited February 18, 2013 by pugpete1108

[calvinhorse 870]

Gti6 stem seals are narrower so the double springs fit over

[pugpete1108 62 1 Cars]

ah right cheers.

 

do they just knock out and knock in? or is it a specialist job?

[JeffR 51]

I remember Sandy posting a diagram of the inlet ports showing the diameters of a few different XU 16v heads, XU7 was significantly smaller.

 

Hey WP, is this what you're referring to?

Edited February 19, 2013 by JeffR

[calvinhorse 870]

Stem seals not valve stems.

 

Stem seals you can carefully pull off with long pliers and push new ones on with an 11mm socket on an extension bar. That's how I've always done it anyway

[welshpug 1,657]

thats the one Jeff.

 

 

XU7 and 10J4R stem seals are part of the lower spring seat, which isnt the right shape for the double springs.

[pugpete1108 62 1 Cars]

I remember Sandy posting a diagram of the inlet ports showing the diameters of a few different XU 16v heads, XU7 was significantly smaller.

 

Hey WP, is this what you're referring to?

nice find, although it does show the inlet as being a 5mm difference in diameter between the xu7 and the xu10 whereas mine are exactly the same? im going to have to strip it and have a good measure.

i have been in contact with sandy who offered me dixons old race xu7 head but seeing as im off to the us pretty soon i really cant afford it yet. maybe later in the year.

 

Stem seals not valve stems.

 

Stem seals you can carefully pull off with long pliers and push new ones on with an 11mm socket on an extension bar. That's how I've always done it anyway

yeah i thought i would have a read up and figured it out now, haynes state to replace these regardless so are they still available from pug? i guess i would order the xu10rs ones?

[calvinhorse 870]

Gti6 cams need gti6 spring seats, gti6 double springs and gti6 stem seals.

 

They all fit into a 2.0 xsi head and I'm sure xu7 head is physically the same.

[calvinhorse 870]

Gti6 stem seals are available from pug for £1.24 ish each in packs of five so you have to buy 20.. Good Ol pug!

[pugpete1108 62 1 Cars]

well after removing the valves its easy to see how restricted the inlet is in the throat.

 

 

out with the grinder then i guess.

Edited February 21, 2013 by pugpete1108

[DamirGTI 342]

Yes , this heads have terrible triangle kinda throat shape .. but leaves you quite a lot of fun of reshaping it , if you're handy with the grinder and have a feel how it needs to be done , this one isn't a hard to DIY porting

 

D

[pugpete1108 62 1 Cars]

right well going by the haynes data my head is 20mm too short

 

says 157.4 - 157.7mm mine is measuring 137.4mm

 

anyone know the min/max head size for an xu7? as the haynes is quite clearly lying (or im measuring it wrong)

[DamirGTI 342]

From the OE service book :

 

nominal - 137 +/- 0.05

 

regrind 0.2 mm - 136.8 +/- 0.05

 

.. so that's fine .

 

 

D

Edited February 22, 2013 by DamirGTI

[pugpete1108 62 1 Cars]

brill cheers Damir

[pugpete1108 62 1 Cars]

got the rs head stripped down at the weekend and its clear to see how much room for improovment there is.

 

the valve guides (if the same size?) are set right in to the casting instead of protruding.

 

ive order a set of carbide burrs along with a load of sand paper drums so when they turn up i can crack on.

 

not sure if im going to open them up as far as the rs head, but we will see how i get on.

 

heres some pics for comparison

 

 

Edited February 25, 2013 by pugpete1108

[DamirGTI 342]

Loads of varieties for making an really good ported head from this one , cos it's so much restrictive and it's almost obvious which areas you must reshape ..

 

I started engine porting 6 years ago (not just the PSA engines .. all makes/brands) , loads of fun !! and always had good results

 

This man helped me a lot back in the days , so really a must to visit :

 

http://www.guy-croft.com/

 

.. and "my vinyl" , first porting attempt of a 1.9 D6B head :

 

http://forum.205gtidrivers.com/index.php?showtopic=69859

 

(ended up so good DIY porting job that i couldn't believe ! .. so i became cylinder head porting addictive )

 

D

Edited February 25, 2013 by DamirGTI

[pugpete1108 62 1 Cars]

my burrs turned up today and seeing as i got a cheeky half shift from work i set about it.

 

its not too bad once you get into it but not sure if i could do it for a living.

 

anyway i started by rounding off the throat to about 30mm then worked round to the entry and took that out to 40mm. it will need some more work but just getting it nearly there is a real bonus.

 

i need some polishing bits now just to smooth it all out then crack on with the next 7

 

 

 

hopefully im doing it right?

[pip470 61]

I think if it looks right then it most probably is. Its definitely better than it was. Nice work mate.