Porting & Polishing?

If you can replace a headgasket, and take time to read a good book, and find a scrap head to practice on, it is something you can do yourself.

You can do it yourself. All you need is something like a dremel.

Quite involved. It involves grinding away the inlet/exhaust ports in the head to match the alignment of the inlet/exhaust manifold as well as altering the shape of the ports then polish to smooth/increase airflow. On the pintos you used to creat an apple shape where the port turned towards the cylinder to greatly increase airflow.

Its a bit of a black art.

If done by a pro there is not much to be gained. UNLESS you fit bigger valves, carefully shape valve seats, etc. And then, you really need the manifolds, intake and exhausts to match or you are wasting your time.

After all of that dont expect huge power gains unless you fit a better race cam, and remap/rejet it. And even then, you will be lucky to get a 25 percent increase.

General: there are some good bits on the web about porting this one:

is American (so aimed at big V8s) and a bit commercial, but gives the general idea. What engine is it? It makes a lot of difference - both on the amount of info (i.e. people who have done it before!!) and how effective it will be. Some engines respond really well and on others its a complete waste of time.

I'm half way through "porting and polishing" on my 1.4 K-series. Funnily enough, the best port do on these isn't actually anything to do with the breathing, it is actually to remove all the casting flash from around the coolant channels. I must have nearly doubled the size of the channels by just taking them back to what had been originally designed.

I'd imagine it is the 106 judging by his other post.

Yep, well guessed!

I've got a 106 1.4xsi which I'm planning to port/polish when I take head off to fit a cam. Does anyone have any experience on these 1.4 TU engines? My girlfriend has 1.1ltr 106, would it be a complete waste of time on this as I'm desperate to tune it as much as possible for her too.........

I would have thought there would be plenty of info on the TU engine. It has been around for a while. I'll check with a couple of friends that rally Pugs and Cits.

The 1.4 is a waste of time too.

Cars like these are made as cheap and light as possible. They are for town use getting groceries. So apart from a small weedy engine it also will have tiny brakes at both ends, lightweight shopping style shocks and springs etc. The whole vehicle, and this aplies to the majority of front drive small engine cars, is a carefully designed package. Doing anything to the engine that actually gives any real extra power means it is now horrible to drive and has brakes that are too weedy to stop it. However, simply diy porting the head with stock valves does not fall into this catogory...It is unlikely to achieve more than a couple of percent power increase.

Its not for nothing that the faster versions have different gear ratios, different diffs and types of diff, as well as different suspension and geometry, oil coolers, bigger radiators, gearboxes and bifgger clutches, stiffer anti roll bars, wider wheels, etc etc...

If you really wanted a faster car why didnt you start with a car that was already built like this? Tuning work only really makes any sense at all when you already have the fastest car in the range and want or need more.

Otherwise it inevitably means that you are throwing good money after bad and finishing up with a peaky, unreliable noisey, evil handling car that does not stop properly, and is all but impossible to insure!

Plus if you are going to tune an engine, start with the biggest! 10 percent more on a 200bhp motor is an extra 20bhp. The same 10% impovement on a

50bhp grocery getter costs the same in parts and gives only 2.5bhp extra!

Any single engine tuning mod will not do mutch anyway. Ports, valves, manifolds, carbs/throttle bodies, exhaust systems, cams, and compression ratios all work together. Adding a BIG exhaust does not help hardly at all for example as the cam timing is mild, and not effected much by backpressure. All there things need to be changed and remapped together to see real power gains, and a bigger engined car from the same range will still be more reliable and nicer to drive! And cheaper.

Speak for your own experiences in small cars.

Mine is lowered 40mm all round, with Koni dampers & springs on the front, handles perfect. OK, brakes aren't the best, but greenstuff pads keep it tight when it needs it.

So far I have induction, full thro GPN exhaust with GMC 4-1 manifold, lightened & balanced flywheel, uprated clutch & recent rebuild with full valve regrind, etc....... Next stage is cam, port & polish and a chip.

The car is pre-cat and has 100bhp as standard, so by my reckoning I could get 130 ish........ Not bad for a small 106. Still reckon it would have cost less than a semi decent 106GTI with the same sort of power. Insurance isn't that bad either.

For all its mods, it sounds good if nothing else!

I have been thinking of swapping for 205GTI though....................

130 possibly, rolling road before and after, because you may be surprised how hard it is to get 30bhp extra...

Even if it does 130bhp its a small increase really, and almost certainly its worse at the bottom end and less refined to drive. And less economical too?

The gti undoubtedly also has better resale, and countless different parts as my first description shows. Making it a better car?

If you are doing the head do yourself a favour and get bigger valves stuck in, THEY are the main restriction! And remember a bigger lumpier cam NEEDS higher compression ratio to work. Less trapping volume!

Now if you had done all that to the gti it would make more sense!

Yeah, fair do, it will be awkward to get that extra 30bhp, but thats where all the fun lies isn't it.

I've had the XSI some time now, and I've done these mods over the time I've had it, so maybe it is time to upgrade. The XSI was cheap to insure after I was banned (I had MK2 Golf GTI before), whilst still being decent to drive.

The thing with internal engine mods is insurance need never know about most stuff. How the hell do they know if the head has been ported and a cam fitted?

Because a race cam / big valves means it will need a straight through loud exhaust, idle all raspy and agitated, and lumpily!

A race engine sounds DIFFERENT massively. If it doesent its not going to go any better...

ROFLMAO....

Yeah if you throw serious money at the motor and by that point it'll be virtually undrivable cos you'd have to rev it to 3000RPM just to set off from standstill.

Try nearly impossible.

THe popping on overrun. The fact it has an idle as smooth as the rocky mountains. The fact you need to rev it to 3000RPM just so you can set off.

5bhp extra, surely

And when was the last time you had the insurance man stood at the side of you checking for popping on overrun?

30% is a big improvement I know, but I doubt its 'unreachable'

bloody hell thats 2 ppl that moaned about 5 instead of 2.5....is it that important its worth a post???

stop wasting money on the car...the minute u buy/drive a better car u will instantly regret spending all that money and understand what everyone is going on about.

next time you smash into someone, he will be standing next to your car like the grim reaper inspecting every inch of it to get out of helping you.