Webber/Dellorto inlets

[west2.1]

Hi,maybe a silly question, but...

I've seen different lenghts of inlet manifolds for above carbs, and wondered what the difference is, and is longer better than shorter, or other way around, or is it as simple as clearance on different engines?

Thanks for answering .

Paul.

[Big R]

Paul - depends if you are looking for neat packaging or the most efficient set up.  

If you are wanting the engine to breath at its optimum, you want the distance from the inlet valve head to the end of the air horn to be a specific length.  This length varies depending on the engine type and at what point in the rev range you expect maximum power and torque.  

You need advice from someone with the same spec of engine as you have.  If you can provide an engine spec, I’m sure someone will be able to tell you what works for them.

[markcoopers]

That small technical point aside, big is best  

[BuGsBuNnY]

A good starting point is the same length trumpets as the inlet track. As luck would have it, I have some small trumpets for sale here:

click me

[Bronco Jr]

This is quite a big issue and has been discussed on here before, try searching...

IIRC Dave andrews website has some good information on this. It goes hand in hand with choke size I believe and is also a question of the charicteristics your looking for from your engine (eg more torque)

Probably  the best thing is to gather data then talk to a specialist and maybe do a rolling road as its often the case that people try to fine tune something when the basics are not right and just b******* everything up (I do anyway...)

Good Hunting

[west2.1]

Thanks for input on this topic, much appreciated. I have seen on Vulcan website they polish their inlet manifolds, but  i have read that they should be rough cast finish to aid better atomising...... any views on this?

Paul

[Chasmon]

Personal opinion is that the velocity stacks should be smooth but you want a rougher surface once fuel is introduced as otherwise it will precipitate and cause droplets on the smooth surfaces.... I wait to be corrected though

[Big R]

depends on how you want to run the engine - at higher air speeds a smooth inlet would be prefereable as fuel drop out would be minimable, where as at lower air speeds fuel drop out is more of a problem and a slightly rougher surface would be preferable.  As air speed is impacted by engine revs, choke sizes etc, you have plenty of variables to play with.  Good luck  

[BuGsBuNnY]

Excellent website here: http://www.dcoe.net/info.htm

Sam really knows his stuff!

[west2.1]

Thanks for the link Bugs, lots of useful info there>

Paul