Aftermarket Inlet Manifold Sizzing

[Kevp]

Iv asked before but in a different post so had a pore response.

Is the manifold aperture size to head aperture size critical?
Particularly if the throttle bodies are say 45s & the manifold holds true to this size, but the head has a larger port area. Does this matter?

My application is a Blacktop Zetec or ST170, Where the block apertures are larger than the aftermarket manifolds seem to be. I realise air flow (speed)will be reduced once it hits the head. But presumably getting a manifold from 45mm dia to 50mm dia (or whatever head port size is) will be reduced anyway?

Confused of any losses or gains if at all.
Thanks

[Pumaracing]

Flow doesn't mind going from a smaller section to a larger one (within limits) so if it's just a tad smaller everywhere I wouldn't fret about it. However that's not to say that the manifold is the optimal shape or size to start with and no one can answer that without seeing it or flowtesting it. Usually you can get a bit more flow out of them and in some cases a lot more.

[magpies]

Sorry to jump on you thread

Pumaracing said:

Flow doesn't mind going from a smaller section to a larger one (within limits) so if it's just a tad smaller everywhere I wouldn't fret about it. However that's not to say that the manifold is the optimal shape or size to start with and no one can answer that without seeing it or flowtesting it. Usually you can get a bit more flow out of them and in some cases a lot more.

Fancy that - pumaracing giving a straigh foreward answer and no sarcasm

[Mr2Mike]

magpies said:

Fancy that - pumaracing giving a straigh foreward answer and no sarcasm

He always gives good advice if sensible questions are asked IME.

[Kevp]

yea. I Thought it was a sensable question as well. Thanks.