Power Gains With Xu10 Head

[wardy18 33 1 Cars]

What (if any) gains would you expect to see in simply swapping a Xu9 8v head with a Xu10 8v head on a 1.9 bottom end on 45 webers with a strong rally cam? Is there any gains to be had with simply boltin on this bigger valved head an not doin any porting work, jus a slight skim ?

[martin81 1]

What (if any) gains would you expect to see in simply swapping a Xu9 8v head with a Xu10 8v head on a 1.9 bottom end on 45 webers with a strong rally cam? Is there any gains to be had with simply boltin on this bigger valved head an not doin any porting work, jus a slight skim ?

 

Im doing same conversion, but on my cti (105bhp), and the head alone would give me approx 15 bhp or so. With new cam(still haven't found out which exactly) and xu10 the result should be 145-150 bhp.

 

But remember you need to portmatch both manifold and head.. Not an exact match- but enough...

 

It should be a great and cheap conversion, espessialy(?) on cti's/rallyes

 

Martin

[brianthemagical 1]

Off the top of my head the compression ratio is all wrong.

[Anthony 1,000]

I've done the swap, although running standard injection and a mild PT36 cam.

 

It does work and few that have been in my car would say that it's slow for an 8v, and it's still going strong after over 20k miles. I've never rolling-roaded mine as how it drives is more important to me that a power graph with some figures, but I'd guess around 135-140hp.

 

As above, the head needs to be heavily skimmed to sort the compression ratio out (about 1.6mm off the top of my head for about 10.2:1) and you'll need to dig the dremel out to reshape the inlet ports to match XU9 ones on your carb inlet.

[wardy18 33 1 Cars]

so not really a simple swap then, im currently running 10.9cr so would need a massive skim or some high cr pistons!!

 

hmm will look into this a bit more, i just need cheap upgrades until i can afford to get a BV head ported polished etc

[Baz 421]

I wouldn't bother with a BV head, just go for the Xu10 head, if you want bigger valves still, do it to that. Well worth the work. Anthony's isn't slow at all!

[martin81 1]

the more you skim of, the higher the c/r...

And im doing it on a cti, not gti

[taffycrook 2]

Did this a couple of years ago on a 1600 rally car.

Used group A cam and xu10 head skimmed and port matched.

On injection it was quick and won its class on a few rallies, it was decided more power was needed but it was left alone untill it had won the national gravel 1600 title. It made about 128 bhp and required an increase in fuel pressure to keep the mixture rich enough.

Once on carbs 40's and mapped ignition it made 140 bhp after some careful mapping and intake length changes.

Hasn't done many events like this but when it does it keeps up with most.

[Jakob 1]

XU10 valves are bigger. When you put bigger valves in smaller bore, you dont necesarely get better flow. I have a bad fealing that you actually get, if lucky, the same flow. Std. bore is 86mm on XU10 vs. 83mm on XU9. It is the flow around the valve to the wall that is critical.

 

It is quite often to see threads saying "Help, power needed on Xu10 head swap" ....

 

Ported XU9 GTI head with PT36 cam and KN filter, responds solid 155hp on a standard CTI (no cat / 150hp with cat) @ 6200rpm. To me, most of the XU10 head swaps I have read givs around 140hp. This is based on the assumption that XU10 head flows like ported XU9 head, and GTI cam are almost like PT36, if not also pt36 or simular pt46 . KN filter mandetory.