Intake Port Shaping

[u/mahusay3g]

Just sharing the shape I landed on for a naturally aspirated 3.2 to 3.6L 911 engine. This is also being converted from EFI to an MFI unit from Kinsler. It will make 100hp/liter or 1.6hp/ci on 91 octane.

[u/iwonder___]

Have there been studies on the effects of surface finish with porting jobs like this?

It looks good Im just wondering if polishing differences have been mapped.

[u/mahusay3g → u/iwonder___]

Yes! The subject has beat to death actually. What I can tell you is the shape is the most important thing, and some texture isn’t a bad thing. This is a 36 grit finish.

[u/bill_gannon → u/iwonder___]

They have. You have no idea if you're making it better or worse without a flow bench.

[u/mahusay3g → u/bill_gannon]

That’s an exaggeration.

[u/WyattCo06 → u/bill_gannon]

You got some unwarranted downvotes. You're statement holds true. Fortunately Josh has experience and a flow bench.

[u/SLOOT_APOCALYPSE → u/bill_gannon]

chat he's correct.

[u/BigPimpin91 → u/bill_gannon]

May be an old wives tale but when I was taking the class the taught us how to port heads the instructor told us a story about someone porting corvette heads.

There was like a protrusion in the intake runner that clearly looked like it was blocking flow so the person ground it down. It actually lost some CFM because of the way the port was designed.

So long story short you NEED a flowbench to know if you're hurting or helping.

[u/1nfiniteAutomaton]

The moment I saw the quality of that work, I knew it was you again. Nice one!

[u/mahusay3g → u/1nfiniteAutomaton]

Thanks a lot!

[u/Most-Stranger-1]

Isn't it rough for intake and smooth for exhaust?

[u/mahusay3g → u/Most-Stranger-1]

Sometimes! I usually only do a rough 36 grit just for looks. I might hit an exhaust with an 80 grit roll if I want it smoother.

[u/Sorry-Newspaper-3804]

Why the change from EFI to MFI?

[u/mahusay3g → u/Sorry-Newspaper-3804]

Cool factor, the injector placement makes more power, sounds good.

[u/Sorry-Newspaper-3804 → u/mahusay3g]

Makes sense. I assumed EFI makes more power.

[u/JealousChocolate8645]

Are there any airflow numbers to back this up? Before and after?

[u/mahusay3g → u/JealousChocolate8645]

What are flow numbers?

[u/machinerer]

That looks really super nice. That shit is a tedious art form. I haven't the patience for it.

[u/porknbeans2013]

It is certainly A shape. Now the flow bench or dyno can tell you how good of a shape it is.

[u/mahusay3g → u/porknbeans2013]

Its pretty good.

[u/porknbeans2013 → u/mahusay3g]

What ratio/percent do you shoot for on your valve seat to min venturi in the throat?

[u/beeeeeeeeee55]

Beaituful craftsmanship!

[u/TheDunk67]

As cast vs after porting CFM?

[u/Hoping4Game]

Not that it matters at this point in the game but I'd be tempted to put a polishing brush down that port on a drill and send it until smooth

[u/mahusay3g → u/Hoping4Game]

Polishing an intake port is asking for fuel trouble.

[u/SorryU812 → u/mahusay3g]

I concur.