K series inlet tract/plenum alignment

[garybee]

Should there be a spacer/bush in the mounting holes of the inlet manifold to ensure decent port alignment?  I have a couple of spare aluminium plenums in my garage and they have holes only slightly larger than the 8mm mounting bolts. 

The plastic plenum has a brass bush that is far larger than the bolts and looks like it would allow a huge degree of movement between it and the head with no guarantee of reasonable port alignment.  Is there something missing?

[oilyhands]

No it is use typical production engineering on a volume product. There is some mileage in easing the port entry so that it is larger then the manifold runner around all its circumference to avoid a step in the inlet tract. However there are other areas in the plenum that cause a worse disruption to airflow, flashing from the moulding process is present in the plenum runners which inhibits airflow, there are some horrible edges just after the throttle body which can be contoured and the TB itself has a ledge around the entry which incoming air will meet head on.

Oily

[garybee]

Thanks Dave,

I suspected that's how it was supposed to be but the difference between that and the VVC plenum had me doubting it.  I suppose that plenum is the performance version though so they put a bit more effort in.  I'll probably just make up a couple of bushes with an offset centre hole (eccentric top-hat) so that they can be rotated to align for 'best fit'.  Appreciate the extra info too, very generous of you.

Ta muchly