Hav'nt been around the forum for a while, but have come in on the tail end of the velocity stack issue. Sounds like a great plan, and something I,ve been pondering for a while. I think I've read most of the posts so sorry if go over something thats already been covered.

I assume that this setup will still use the standard airbox and filter as I did'nt see any mention of filters for the bell mouths. I also recall a mention of increasing the length of the stack (I assume the longest standard stack) by 20% to get the desired increase in torque. This gives an overall stack length of 91.2mm. A stack this long will not fit underneath the air filter element, either at the front or back position. At the most you can increase the length by 6mm at the back, and is 1mm too long at the front.

Even if you increased the lengths as far as possible (until they touch the air filter) this must prevent an even in flow of air to all the circumference of the bell mouth. What effect will this have on performance

I don't mean to rain on anyones parade, just a few issues I hope someone can clarify.

 

Who says you want more torque? The big twin has plenty of that already. I think the key design improvement is the ability to flow more air with less resistance, therefore packing more into the cylinders.

 

Reb - I have not looked myself, but others have discussed how they have bought a second OEM long stack and and replaced the short stack with that. No one has ever mentioned filter clearance.
So I'm currious...

 

I was wondering the same. I had been thinking of cutting the filter out, adding something like 1/2" frame around hole, and mounting filter on that to give clearance. Obviousll needs clearance to the lid of the box still

 

I'm assuming you are still on the topic of the velocity stack being long, or at least longer than stock. Going that route would produce more low-end with a little hit on the top. The machined version discussed in this thread is not significantly longer than stock but rather has a different shape that is more efficient. Filter clearance isn't an issue unless you fabricate stacks that are really long, and I'm not really sure why you would want to do that.

 

I was of the understanding that these are a shade longer than the stock long unit, so was wondering if clearance would become a problem.

 

They should be about 20% longer than the longest oem stack...
And with the length of that at around 4-5 inches, it should make the difference in actual size around or possibly less than half an inch?

And the airbox most definitely has room for that without any modifications to the filter...