inlet manifolds-can they make a difference?

Discussion in 'Engine Gearbox' started by Dutty999, Mar 7, 2016.

  1. Hi all!
    I'm putting twin 40IDFs onto my 1700 type 4 engine. The thing is there is a vast price difference between the available performance inlet manifolds!
    Can/so they make a recognisable difference or is it just a styling/sales gimmick?
  2. Inlet manifolds are just pieces that the petrol follows though ,the smoother the run the better performance...

    for extra power ,it is the carbe ,engine ...

    so imo no difference...
  3. You get a generic one size fits all, 48 MM or sized 40 MM ones to suit the carb .... It will make a difference but by how much I'm guessing not a lot ....same as filter bases and velocity stacks should all be the same size with no steps
  4. two schools: one says match ported inlets with same size venturis as your carb improves air flow....the other says match ported inlets with a venturi larger than your carb acts like a plenum...better for atomization....I doubt whether you'll notice a huge difference either way, unless you're trying to squeeze the very last ounce of performance from well chosen components...

    the common ground is match porting....this is worth doing, especially if you're also considering gas flowing the heads....otherwise, go for the cheapest you can find, clean up any flashing on the insides and bolt them on with fibre gaskets....CSPs fit well...and IIRC Deimos aircooled were doing some nice ones...just checked and they've sold 'em
  5. That's brilliant cheers, although I have no idea what has flowing is! More reading required!
    That's really helpful though, thanks
  6. Gas flowing is simply improving the journey that the fuel and air mixture makes, from the carb to the cylinder, and out again via the exhaust, once it's been burnt....achieved by carefully reshaping the internal passages (ports) inside the cylinder head. Valve angles also need to be corrected to improve the flow....anything that presents a corner, step or ledge on this journey, reduces flow, as @lhu1281 mentioned...
    Last edited: Mar 7, 2016
  7. Wow! Cheers that's great knowledge....thanks guys, you can't beat experience!
  8. I started out by buggering around with 2 stroke motorbikes which, to be fair, are much less complicated...did a few minis with great results, but I've never got around to doing my do it well, you need some heads to practice on, a decent die grinder and a flow bench to test the changes you make...and lots of patience; quite a bit is trial and error...
  9. You forgot to mention...dedication!
    I'd love to be like you alas I rarely have time!

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