Port Matching 3.2 Intake to 3.3 Heads

[AnotherPorsche2]

I am port matching my 3.3 heads to my Carrera 3.2 intake and had a few questions I was hoping you could help me out with.

I have attached a picture to clarify and provide a reference for others

Question 1: What gasket are people using between the spacer and the head? The 3.2 gasket is too large for the 3.3 head surface as can be seen in picture #4. If you notice the 3.2 insert picture on #1, the 3.2 head has more surface.

Question #2: Since the 3.3 head has less surface area than a 3.2, the surface area where the injector is can’t be machined to match the intake/spacer and still leave enough surface for the gasket to seal. This can be seen in pictures #2-4 where the red area represents the surface to be trimmed. Will leaving this cause issues with the injector spray pattern? How much more can I trim this and still have enough surface area for the gasket?

Question #3: How rough do I leave the ported surface? Everything I read indicates that the intake side of the head should not be polished to a smooth surface.

BTW, picture #1 shows the 3.3 head before porting. The green area represents the area that needs to be removed. The blue line matches the 3.2 intake gasket and was not removed. I used the intake spacers for a template.

[smestas]

Bump

[jluetjen]

Hi Simon;
Can you update us on what the objectives are for your project. Why are you using a 3.2 manifold with 3.3 (turbo?) heads?

The reason that I'm asking is because if my memory is correct, the 3.3 heads were optimised for a turbo engine and as a result would be a poor match for a normally asperated engine. If you're building a turbo, the proposed solution to your problem may be different then the solution for a NA engine. One of the secrets of making a successful turbo engine is to optimise the entire intake tract to support spooling up the turbo. Unfortunately I'm not real familiar with those "secrets" beyond knowing that they exist.

[beepbeep]

Originally posted by jluetjen
Hi Simon;
Can you update us on what the objectives are for your project. Why are you using a 3.2 manifold with 3.3 (turbo?) heads?

The reason that I'm asking is because if my memory is correct, the 3.3 heads were optimised for a turbo engine and as a result would be a poor match for a normally asperated engine. If you're building a turbo, the proposed solution to your problem may be different then the solution for a NA engine. One of the secrets of making a successful turbo engine is to optimise the entire intake tract to support spooling up the turbo. Unfortunately I'm not real familiar with those "secrets" beyond knowing that they exist.

930 heads are "strangled" in order to boost gas velocity in inake ports, a half assed low tech solution Porsche did to make low RPM torque little better back in dark ages. Those heads are in no way optimal for this car as they don't flow too well. I bet he's using Carrera plenum in order to install EFI and get rid of that pesky CIS. This is usual thing to do in such case: port the intake so it matches.

Original poster (what's your name?): CIS and EFI injectors usually have different spray patterns as CIS runs of different fuel-pressure. I would recommend you to port-match and slightly polish intake-port. Talking about spray-groove...just open it as much as you can without making a hole in the wall. Leave at least 2 mm of material there so you don't mess upp structural rigidity.

It's not sooo dangerous to get some spray on the wall...what happends is that it condensates and gives slightly worse smog readings. Think about carbs, in that case, spray needs to travel all the way trough the plenum!

And yeay, please tell us more about your CIS-to-EFI conversion!

P.S. You can use "golf ball dent trick" in those spray-grooves: