914/6 Intake Manifold Question Options

[Peeterabytes]

I am in the process of getting my 914/6 back on the road after sitting in my garage for 24 years. Finished the fuel tank, suspension, and brakes rebuild so on to replacing the Webers with some 40mm PMOs. The car has a 911 3.0 SC engine.

The current intake manifolds are 901.108.321 which I believe my father got from a 911s back in the day. Believe those are 32mm ports.

I am thinking about replacing them with new PMO intake manifolds but on the PMB website, it suggests 36mm X 40mm or 37mm X 40mm for 3.0 engine. I am thinking the 36mm. Only because I believe that is the intake port size for SC engines. And I’m just looking to make it a fun casual driver, not any crazy performance or worrying about where my peak HP comes in.

Asking you experts for advice? Stick with the 32s? Get the 36s? Or?

[technicalninja]

Usually reducing port diameter will increase port velocity and help cylinder filling at lower RPMS.

I have a 98 E36 M3 and it came with an intake manifold that is significantly smaller in port size than the runners in the head. Like 10-15% smaller.

This skinny port manifold (S52) made 5-10 lbs/ft more torque below 4k RPM.
It made the same HP as the earlier S50 manifold which had ports that matched the size in the heads.
This makes the car a little bit quicker.

Now, as soon as you add compression, cams, or any other VE improvers the skinny manifold is a restriction, and EVERYONE installs a S50 manifold which thankfully are common (all pre 96 3 series have one, not just M3s).

For what the OP intends I'd get the 32s and try them first before I ported them out.
They might work better "as is" for his wants...