power cones for roundtop carbs

[5thhorsemann]

So I've done some searching, and can't find the answer I'm looking for so I'll just ask the experts. (Shameless ego stroking, isn't it)

The car is a 73, original motor with 72 RT carbs and intake. I'm running the dual K&N round air filters, 3 1/4 inches deep. What are the best power cones to install in the K&N filters? Is anyone using this setup with success?

[30 Ounce]

Velocity Stacks? Air Horms? This is what I'm running and they work well. http://www.thezstore.com/page/TZS/PROD/PFFC20/11-4010KI Never heard them called power cones so I'm not sure if this is what your looking for.

[5thhorsemann]

Yea, AIR HORNS, pardon my mental block.

[Bruce Palmer]

I run the billet stub stacks on my 46s just because chicks dig 'em.... www.aptfast.com

Anything that will roll the air into the carb vs breaking it hard over that 90 degree edge will help.

[5thhorsemann]

I just dont want a stack thats too high, or that fits too closely to the filter cover, also not all that intrested in spending $100 for a set.

[240260280z]

Read this stuff:

http://www.classiczcars.com/forums/showthread.php?43229-SU-Mod-(lifted-from-the-net)

[5thhorsemann]

Blue, I like the bell mouth doughnut, They would kill alot of the birds that concern me with one stone, do you know of a supplier?

[madkaw]

I run the billet stub stacks on my 46s just because chicks dig 'em.... www.aptfast.com

Anything that will roll the air into the carb vs breaking it hard over that 90 degree edge will help.

Bruce-you crack me upLOL

[240260280z]

K&N make some but they don't look right. Check dia too: EBAY in NJ http://www.ebay.com/itm/K-N-Stub-Stack-85-5039-/310221606530?hash=item483aa60e82&item=310221606530&pt=Motors_Car_Truck_Parts_Accessories&vxp=mtr#ht_2229wt_1140

It seems that UK is where to get the better shaped ones. (Or Brit Car Enthusiast / Vendor http://www.mgexperience.net/phorum/read.php?42,544271)

I would recommend taking a carb and photo to a machine shop and have them make two on lathes.

[jmortensen]

You can cut the stock ones out of your original air cleaner if you still have it. That's what I did. The difference between no air horns and the $250 ones is probably no more than a few hp, so I wouldn't go too overboard.

[240260280z]

[jmortensen]

OK, I'll dig a little deeper. In practice, it looks like the stock airhorns HURT performance:

In real world track testing with air rushing over the engine compartment I ran faster track times without the stock airhorns.

I tried it a number of times on the same day and it was consistently slower with the stock airhorns installed as opposed to just the carb body entrance.

The sharp edges on the stock airhorns DISRUPT and hinder airflow.

If the edges had a good 270 degree roll then there would be an increase in airflow.

David Vizard has written a carb tuning book and it has a small section on SU carbs with Dyno graphs that SHOW a LOSS of HP with nonradiused airhorns.

He showed a 4% increse in HP with a properly radiused 4" air horn.

He showed a 5% increase in HP with a 1" stub stack.

He made an 18" long air horn and showed an enormous increase in low end torque in the realm of 10% but the HP obviously dropped way down.

Since installing my home made stub stacks my drag times have improved over just the bare carb body entrance. A consistent half mph increase would indicate an increase of about 4 HP through the better controlled air entryway.

If you have time go by Barnes and Nobles and look at the David Vizard Carb book.

later,norm

So you're talking 4 hp for Norm, who was wringing quite a bit of power out of a weird setup with two headgaskets and hand-sanded pistons and rocker arms. The average Joe who is driving to work and back is probably not going to notice one way or the other.

From: http://forums.hybridz.org/index.php/topic/11877-aftermarket-air-horns-sus-do-they-help-any/page__view__findpost__p__85474

Edited November 7, 2011 by jmortensen