Port Matching - QUESTION

[Gd78]

Hey everyone

I started to remove the inlet manifolds to port match them this weekend. Firstly my 172 ph2 is already fitted with an RS stamped lower inlet, which is good. I have taken the top one off to have a look at the mating surfaces and markings on the gaskets and whilst having a look I noticed that at the head end of the lower inlet the surface looks like it has been machined in some way.

Question: should the lower inlet have the typical casting surface or at the head side are they partially machined as standard. I am assuming they should be without machining but as I've never done this before I wanted to check.

I have attached picture but to be honest it's not the best but it's best I can get.

thanks

 

[NorthloopCup]

The machined part you can see in that picture is the cylinder head inlet ports mate. They're cnc'd from the factory.

 

[Gd78]

Thanks for that.
When I looked down the manifold I couldn't see any joint between the head and the manifold so assumed it was part of the manifold.

I'll take it off tomorrow and have a proper look.

Thanks

 

[Gd78]

Ine other quick question if you dont mind. I am sure I read it somewhere on here are RS manifolds not really worth porting?

 

[NorthloopCup]

Ine other quick question if you dont mind. I am sure I read it somewhere on here are RS manifolds not really worth porting?

Not really mate no. Match the upper to the lower half but leave the rest. Only my opinion though.

 

[trenace188]

Remove top inlet
Bolt gasket to top inlet
draw around
The dremmel away

 

[Carlv8415]

It's all about flow so make it smooth as possible

 

[Gd78]

Thanks for input.

Presumably I should compare the gasket fit on both parts to ensure matching.

 

[warwickstingray]

I'd leave them a smidge smaller than the gasket holes unless you gonna take the time to see how the two manifold halves match up. You don't want a step up for the air to cross. A small step down is less of an issue.

 

[Gd78]

Thanks

I have a set of digital calipers so I was going to use them to measure the port sizes.

 

[warwickstingray]

I used to use engineers blue but it was a bit hit and miss.

 

[ALD]

Trust me when I say that the heads respond well to head work. Everyone I've done for people on here have had great results from them on the Dyno. Inlet porting has very minimal gains if not none from inlet work..