This is called "tuned" manifold, and one can improve volumetric >efficiency (possibly over 100%) with the tuning effect. The bad news is >that >the tuning is most effective for one engine speed, and the effects trail >off as >you deviate more from that speed (and can actually can reduce performance >for >speeds too far from the target speed, wither too high or too low). I believe the main problem with these was fuel distribution. With the carbs so far from the chamber, the fuel had plenty of time to puddle in the manifold. It would be a super cool set up if combined with modern EFI and you put injector bosses at each cylinder. What RPM were they set up for? I used to think long = high rpm, but now I'm not so sure, isn't it based on the width which determines the velocity of the intake air? If you look at a GM TPI engine they have those tubes which go over the engine and they are really quite similar, except they are a lot less visually dramatic. Rob not an engineer _________________________________________________________________ Add photos to your messages with MSN 8. Get 2 months FREE*. http://join.msn.com/?page=features/featuredemail