Head CC'ing

I have the head off my old VW 9A 16v engine that was in my Corrado. I'd already spent many an hour porting with a dremel and indeed sandpaper and my fingers..unfortunately; the result is as follows...

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I am going to replace the valve guides as they were quite worn, with ABF guides as they are apparently slightly shorter, which should aid air flow. But, I didn't do anything to the combustion chambers, so I've seen and heard of people CC'ing there heads. Can anyone recommend a means to do this and what tools/process is required?

I bought a burette from flea bay.It also came with a piece the clear perspex with a hole big enough to put the end of the burrete in.I put a small amount of vaseline around the edge of the combustion chamber on the head for a good seal with the perspex.Then I just filled the burrette with liquid.Its then easy to see how many cc's of liquid your combustion chamber takes.

What is the cast number code on your head ?

dirtytorque wrote:I bought a burette from flea bay.It also came with a piece the clear perspex with a hole big enough to put the end of the burrete in.I put a small amount of vaseline around the edge of the combustion chamber on the head for a good seal with the perspex.Then I just filled the burrette with liquid.Its then easy to see how many cc's of liquid your combustion chamber takes.

What is the cast number code on your head ?

Hmm, interesting, you got a linkie for the burette?

I can't believe I actually went outside at this time of night but the number on the head is 151 103 373

mrbeige wrote:

dirtytorque wrote:I bought a burette from flea bay.It also came with a piece the clear perspex with a hole big enough to put the end of the burrete in.I put a small amount of vaseline around the edge of the combustion chamber on the head for a good seal with the perspex.Then I just filled the burrette with liquid.Its then easy to see how many cc's of liquid your combustion chamber takes.

What is the cast number code on your head ?

Hmm, interesting, you got a linkie for the burette?

I can't believe I actually went outside at this time of night but the number on the head is 151 103 373

I have the same head.

It's 45 cc's

dirtytorque wrote:I have the same head.

It's 45 cc's

Indeed, but they wont be exact, and I've been advised that CC'ing them to get them exact will make for a better performing engine??

Well seeing is believing.
Its about making sure your engine is suitable for your plans.
That is why I did mine.
I could then calculate what my CR would be.

ebay Item number: 140253915828

First of all I wouldn't worry too much about messing in the combustion chamber as you will offset the gains from cc'ing by loss of airflow if you do it incorrectly as the transition from seat to chamber is very important in order to gain max flow.

Next the shorter guides will help you but realistically in the grand scheme of things it is not noticeable enough to worry about.

Bit of advise on the port work up get some 120 grit cartridge rolls and roughen up that port or you will suffer from fuel pooling as the fuel will drop out of the air mixture onto the port surface if you haven't got a bit of turbulance to mix it back in. The way the port is finished right now will result in a loss of torque and ultimatelly hp.

likewise as a final recommendation round the partition of the sharp edge it causes turbulance and drops flow at the main lift range of your cam resulting in loss of power. (When's the last time you saw a sharp leading edge on an airplane wing )

HTH

good luck with the project

If I'm changing the guides anyway then I might as well use the shorter ones?

I was always under the impression that you didn't necessarily want turbulent flow as the spray from the injector would sort the atomisation? I would have expected to require the turbulent flow with carbs, but not injection, but your logic seems sound, so I stand corrected. *goes off to get some 120grit paper*

And again good logic on the partition between the two ports, I was thinking that the sharp edge would help reduce turbulence

What about the exhaust ports? They are currently like the inlet - smooth as a smooth thing..

I to agree that you wouldnt need it rough as the injector sprays almost direct into the chamber.

Interesting comment on the knife edging tho

120 grit is what is considered an intake surface for fuel injected, whereas carburetted would be finishe in 80 grit. Exhaust side the smoother it is the better as less carbon adhesion.