Inlet manifold gasflowing

[Lowe]

In short, is it worth it?

Now by my understanding the inlet manifold is meant to be rough - to add turbulence which then aids the mixture between air and fuel.

By gasflowing it and smoothing it all out wouldn't you reduce this effect and therefore the effectiveness?

[Tumble]

I *think* that Gas-flowing is more a fine tuning of the port surface, rather than just polishing it..... maybe they leave the bits where the swirling effect is created a little bit rough to keep that going, and polish smooth the bits that don't do anything for the swirl to aid the flow of the stuff to the rough bits... just a guess, but someone will deffo know for sure....

[IainB]

Lowe -
Basically it would be as Tumble said - improving the gas flow through the head, but NOT polishing the ports as this has been proven in-efficent (allowing petrol to drop out of the mixture), i.e. removing any casting inaccuracies, removing sharp radius (unless required), improving airflow around the valves by metal removal etc etc.
Have you port matched between the inlet/exhaust manifolds and you head yet - as Im willing to bet they wont match direct from the factory.
Are you thinking of flowing the head yourself? or getting someone to do it for you?

[Lowe]

I wasn't talking about the head guys.

Inlet manifold - I've found another one for a mear 20 quid. It's been suggested to me that since I'll have a spare I can have it sent away for gasflowing.

I'll not be touching the head since I don't have a spare to play with.

[Jiff Lemon]

Bit like puttting wheels on a tomato.
Time consumng and utterly pointless.

As Eazieb said, the best thing would be to have the manifold matched to the head. But even then, the gains you get are minimal. If you were doing a full engine rebuild, it'd be something to have done, but otherwise leave well alone.

[Lowe]

Thought as much, I'll not bother. Same bloke has a GTT head going though that's had some work done on it.. selling the whole lot with new valves and all the rest of it for 45 quid just to get it out his garage.

I've replied to the thread but no reply yet. :'(

[IainB]

Originally posted by Lowe
I wasn't talking about the head guys.

Doh... thats why it says inlet manifold on the original post... Doh!!

Only time Ive 'flowed' my manifolds is to :-

a) remove casting flash
b) open the ports to match manifolds
c) remove areas to increase airflow (usually by following material found on the web or in books)

But then again the engines they have been going on all require max airflow @ WOT
(eagerly awaits delivery of manifold and heads for new engine )
£45 sounds like a bargin for a recon head and new valves wish mine were that cheap !!

[Zak33]

Actually, the best way for INLET isoften a totally different SHAPE.....not the ports etc...the actual casting.

Its often created for size, space, efficiency of production, and NOT for shape...length of inlet tracts etc......

people like Irmscher do one for Astras that is NOTHING LIKE the original and good gains are made.....but BIG DOUGH..your money is best spent elsewhere

[jon bda]

Stick to matching the head and manifold mate...

[hotpurple]

Or make your own from ally tube. Are you running a carb or fuel injection?