DCNF air horns: the 'Kermit Ring' explained

I get asked this a few times a year, so here it is:

The stock DCNF air horns have a 4-5mm lip UNDER the mounting plate that allows for the fat rubber gasket that fits there. Without a lip, this area may have an opening to the main jet chamber and disrupt airflow. Most non-stock (Superformance, Pierce, TWM) DO NOT have this lip beneath the mounting plate, although the Gene Berg Volkswagen stacks do (!!). Former FChatter Kermit used make a set on low profile high flow stacks for the dcnf (seen in background of below photo) and made some rings that fit into the top of the carb which allwed a nice flush fit in the stock Ferrari 308 for his and all velocity stacks that had flat plate mounts.

Here is a picture of a Kermit Ring and what it looks like in a DCNF carb. You can see it allows room for the thick rubber gasket/spacer.

Any 308 going to a non stock air horn application with a flat mounting plate will need a Kermit Ring to work best in the 308 application.

Hope this helps
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cool...........

 

Ok, I see that lip you are talking about.

Yellow arrow.

Ignore the blue marks.
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Russ how much of a difference will these low stacks make?I was looking at the GT4 air filter box and with some plastercine when I closed the engine lid there was about 20mm clearance.I was thinking of making a gasket made of rubber about 15mm thick that fits between the airfilter box lid and the box itself.Would this be a good idea?

 

it's gonna be slow no matter what you do! give up

 

There are a lot of very contentious yet entertaining threads on this and the old board -- in fact just searching on the word 'kermit' will take through a lot of interesting and sometimes weird threads. **In theory** with the shorter air horns you are picking up high end flow at the expense of low end airflow velocity for low end response. Everything is a trade off. In reality, well... I did not measure, but subjectively it seemed this way, but not dramatically. I used them for years and kinda liked them.
In conjunction with the airbox mod removing the silencing, the shorter air horns showed on a Kermit dyno to pick up like 10 hp - but was contested (like everything else on FChat )

As a general rule I have found that as much air you can put above the trumpets is good. Mike Pierce of Pierce Manifolds I believe recommends at least 3/4 inch. I actually am doing something similar to you on an airbox I am building for my car (see below) also uses a thick gasket thingee to at least raise the lid above the trumpets as high as it will go, also about 15 - 20 mm. The main thing is trying to increase air velocity delivered to the air horns from the point of filtration and add the most effective filter element. It's gonna be loud, though.
Good luck!
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Oh, you! Back to your Vegemite!

 

Thanks Russ.I just thought of it the other day when I was at a workshop that specialise in making gaskets.I think for around $30 they should be able to make one up for the experiment

 

You only say that because your car isn't Red;if you had a Red car like mine you would see that its much faster,and I even washed it so that should give it another couple of HP as well

 

Maurice - Have them make two, if possible, and I'll send you the $.
OBTW - if you're interested in the set of the Kermit short air horns just let me know. Maybe we can work out a trade with my weakness for ANZAC Bisuits.