Porting an inline 4

[SoND]

I've been looking it up and have got it into my head to do some porting work on my cbr over the winter but I've never done it before and don't know anyone who's done it themselves so I'm looking for a bit of advice. Not going to rip the engine apart just for this, piston rings are the main reason and figured some tuning wouldn't go amiss while I'm in there.

I know it's more than just opening the ports bigger than they're meant to be and polishing them up but there's a few different methods I've found like gasket matching, head matching or just giving them a new finish so any info would be good.

From what I've read and seen it doesn't appear too difficult just very time consuming (I could be wrong) and if you fuck it up you need a new head, got my eyes on a spare engine just in case. I've found this kit which appears to be everything you need, maybe. https://www.sa-motorsports.com/cat/p5.aspx

[Pete.]

There's so much more to it than you would think you are better-off leaving it to the pros. You need a different finish on the inlets to the exhaust to stop the fuel coming out of suspension, you also need to consider where you take material from as much as how much to take.

There is a school of thought that actually advocates REDUCING the cross-sectional area of the inlets in order to increase intake charge velocity and boost mid-range:

https://www.mototuneusa.com/think_fast.htm
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[Ariel Badger]

Took me about ten hours to port a 350 single head recently. It is hard work but satisfying.
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[SoND]

I'd like to know how they go about making the ports smaller. Building up with weld then regrinding/machining?

I didn't mean you're meant to polish the intakes, it's a slightly rough even finish you need to help fuel evaporate instead of sitting about and smooth for the exhaust to deter carbon build up.

https://www.youtube.com/watch?v=ijlPwA7W29M

This is a video where he is matching the head to the intake which appears sensible enough (says the one who doesn't know any better ), sort of just improving the deficiencies you get from a mass produced cast head.

Would it even be sufficient to give them a fresh surface finish without increasing the internal dimensions too much?

[ZRX61]

[chris-red]

If you can get a new head easily enough why not give it a go?
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[Big Pete]

chances are you arent going to get big gains on a cbr, they are pretty good to start with compared to older stuff like CB and GS motors.

If you want to have a go I would advise getting A G Bells tuning books from Amazon they give a good guide as to whats required, whats good and whats bad.

These ones

https://www.amazon.co.uk/Four-stroke-Performance-Tuning-Practical-Guide/dp/1844253147/ref=sr_1_8?ie=UTF8&s=books&qid=1196263158&sr=1-8


https://www.amazon.co.uk/Modern-Engine-Tuning-Graham-Bell/dp/1859608663/ref=pd_sim_b?ie=UTF8&qid=1196263158&sr=1-8
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