[steve 260z/300zx]

I am looking for comments or advice on the use and shape and size of velocity stacks for 72 SUs.

I am building custom air intakes. Unless I hear otherwise - I will simply cut the stacks to the same as the ones in the stock air cleaner box and taper/round/polish the edges. I am using 1 1/2 inch round aluminium stock. Has anyone tried K&Ns stock air cleaners? Did you notice any horsepower increase? Or did HP decrease as there isn't a stack inside each air cleaner.

Incidentally. The design of my intake is:

Two 6.5x8.5x4 inch K&N filters (approx).
Four plates of aluminium to sandwich them with one plate for each carb drilled out for the throat of the carb and velocity stack inside the air cleaner.

Obviously I can't go any longer than about 3 inches with the stacks as the air filters are only 4 inches deep.

 

[JJs72]

I have a set of ZTherapy rebuilt 50mm carbs and got this advise from Scott and from Dave Rebello; "the best velocity air stacks are the stock ones". As to the K&N filter most everyone swears by/uses them. Many may have done what I did and have made too many changes at the same time to actually feel a difference. Rebello suggests you drill/punch out several 3/4-1 inch holes in the top of the stock air filter cover too. Post a pic of your set-up, I like to see it.

 

[steve 260z/300zx]

Yeah - I am hoping to at least maintain stock performance. At least not make it worse. As you might be able to tell - I am primarily making this mod for aesthetic reasons. There will be 2000 grit sandpaper and aluminium polish involved...

Seriously though - I don't think it will hurt to have two big-ass K&N filters in place of the stocker (72 carbs, N36 manifold (polished), L26 block, smoothed and polished balance tube). I have a 280Z style hood for the car (i.e. vented). I may even seal the bottom of the air cleaners to get the car to suck its air away from the exhaust manifold. Eventually will have exhaust header ceramic coated.

I am just about finished plumbing my fuel system with AN#6 fittings and stainless braided line. I will definitely post some picks when complete. I think my set-up will be reasonably unique.

 

[Duff5000]

what work out better. The stock box thing with the "velocity air stacks" or the or the round bowl shaped things that take the foam filters (without stacks)?

 

[SixBanger]

you can always do this

take off the stock airbox and cut around it right at the outer edge of the rubber seals, paint it a nice shiny color, and drop in a stock replacement K&N. You end up with no vacuum line problems, a nice big open air intake, and retain the stock velocity stacks. Works great for me and sounds even better.