Are there any advantages or disadvantages to using short intake manifolds for dual webers?

http://www.914world.com/bbs2/index.php?sho...p;#entry1573218

Off hand , I'd say incoming intake velocity would be shortened / reduced, heat soak more likely ( closer to head connection ) . Also linkage setup would be a little trickier......
The people that really know will probably chime in shortly....

my $.02....

Jack

Short manifolds are a Very Very Good Thing for the VW 411/412 and anyone putting a Type IV into a Type III body. Because even "baby Webers" don't hardly fit with regular manifolds.

In general, short and fat pipes have a greater flow capacity than skinny narrow pipes. But at lower flow rates, the short and fat pipes have worse velocity. So the shorter manifolds could help top-end power at the expense of mid-range torque and mixture quality. Depending on lots of other factors, of course.

--DD

In general, the longer the intake manifolds, the more low end torque you have. The shorter one tend to shift the power-band to the higher RPM range ...

This is a really complicated issue, you have volume and velocity to balence to the desired engine displacement and rpm range. Do some google searching on intake maniflod flow design.

One more thing, on itakes that do not have a shared plenum you will get a stand off reversion if there is not enough volume in the intake at higher rpm. This means that there is a wave of intake charge that bounces off the closed valve and travels back thru the intake and out the carb then sucked backe down the.intake on valve opening. This can really eff will tuning the engine.

Try searching for video on it.

It all depends on the combo. Cam, carbs, CR, etc, etc, etc. And the differance will be small and only seen on a dyno.

The heat soak issue is easily solved by using the phenolic spacer between the head and intake runner. That does require longer studs on the head, but those can be bought or made super easy!

You might get a little less torque but would be able to use a raintray again, which I think is a nice trade off.
The sync issue is solved by using either one of the 2 cable sync options on the market - and you SHOULD do that no matter what manifolds you use!
Zach

Torque is king in a type four, look at what Raby/HAM uses, they use the tallest manifolds out on the market.

Yep. Tall is best fore us. I used to have shorty bus manifolds and went to the one's pictured above. Night and day!

Jake can (used to?) build a motor that does take advantage of the short ones too, but it is on a high rpm config- probably roller cam, etc.

Get tall manifolds and the tallest velocity stacks you can fit. My stuff came from Aircooled.net.

YES! John's a great guy, one of that top circle of engine builders and parts suppliers, and absolutely no agenda.