Normal or has someone been porting??

[MarkX]

Found this today and wondered if it was standard, doesn't look it but I've not seen another

 

[Knuckles]

That looks like heavily unfinished porting to me

 

[Mr R.]

That's standard mate.

 

[BoatNonce]

Yup, standard.

 

[Knuckles]

That's standard?!

Jesus.

 

[Mr R.]

That's standard?!

Jesus.

CNC machined.

 

[Knuckles]

CNC machined.

I thought the inlet was a casting?

That's gash machining if that's the case

 

[BoatNonce]

*badly* CNC machined.

EFA.

I often wondered what you could do with a bit of sandpaper and some time and simply smooth out the hack job they did, and how much difference that would make.

 

[MarkX]

:up:
Thanks for the replies, bit of a hatchet job for standard! :tongueout:

 

[Mr R.]

I thought the inlet was a casting?

That's gash machining if that's the case

You can see the lines of the tool bit mate.

 

[Knuckles]

You can see the lines of the tool bit mate.

I genuinely thought they were made with a dremel. I'm a cnc machinist and couldn't believe they'd have left the factory like that

 

[bashracing]

Gas flow on heads is 10% finish 90% shape, you could spend all day getting a smooth finish for very little gains. these mk2 heads are s**t even with renaults port work

 

[R3k1355]

Gas flow on heads is 10% finish 90% shape, you could spend all day getting a smooth finish for very little gains. these mk2 heads are s**t even with renaults port work

This.

If your engine has CNC'd ports, 4-1 manifold, sports catalyst and a pretty decent airbox setup from the factory, making under 180bhp from a 2.0l engine is pretty s**t.

 

[Budgie]

Standard, as said.

 

[HarvB]

I genuinely thought they were made with a dremel. I'm a cnc machinist and couldn't believe they'd have left the factory like that

It's all about cost, isn't it really? Building one of these for <£14k means as little expensive machining/head as possible!

 

[loggyboy]

I recall reading many years ago a very smooth surface can be detrimental to flow, as a smooth surface can create drag - obviously the standard finish is beyond just being rough for flow purposes, but still a valid argument.

 

[TheCAB]

I recall reading many years ago a very smooth surface can be detrimental to flow, as a smooth surface can create drag - obviously the standard finish is beyond just being rough for flow purposes, but still a valid argument.

This is true, polished ports, although pleasing to the eye, do very little to improve gas flow through the ports, as a slightly rougher surface can help reduce drag and also can help improve the air fuel mix. The trick in head work is to modify the ports to improve gas flow / speed through the ports and hence get more mixture into the cylinder for a given period of time. Even with the tooling marks left in, the std 172 head actually works very well - the 172 is not slow by any means! That's not saying the head cant be improved though.