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 Impact Bowl Vents for Blow Through 
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Site Admin

Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
Nice job on this example.

Impact Bowl Vents for Blow Through.jpg
Impact Bowl Vents for Blow Through.jpg [ 22.83 KiB | Viewed 416 times ]
Sat Jan 31, 2015 7:34 pm

Joined: Fri Feb 08, 2013 5:52 pm
Posts: 78
Interesting design, thanks for posting the picture!

Does different length of these tubes serve a purpose? Both of them seem to be in the area of the same air speed/pressure (far from the boundary layer).

Sun Feb 01, 2015 7:17 pm

Joined: Mon Dec 29, 2014 1:26 am
Posts: 433
There are nearly endless tuning options with those things. The size of the flare (or no flare at all), the cross section of the part of the tubing they're located in (smaller area tube will have higher airspeed than another spot with larger area), and so on.

Like that example with the divided hat it can get awful fiddly to deal with when the hat has to come off. Another option is to mount the vent tubes upstream of the hat in a section of pipe with their ends sticking out, and then use external hose to connect back to the bowls.

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Sun Feb 01, 2015 8:31 pm

Joined: Thu May 08, 2014 7:47 pm
Posts: 235
Here's my KIS version.

WP_20150208_005.jpg [ 528.88 KiB | Viewed 368 times ]
Fri Feb 13, 2015 1:59 am
Site Admin

Joined: Fri Feb 08, 2013 2:37 pm
Posts: 1744
The purpose of the vent tubes in the picture in the first post is to vent the bowl at a location where the flow impact pressure will influence the bowl pressure.

It is similar to the vent location in many carburetors, for example Rochester 2G and 4G, many OE Carter AFBs and many others which use an upward facing slash-cut tube facing into the flow just inside the air horn entrance.

In blow-through applications, the hat geometry and orientation of the entrance cause flow direction and velocity anomalies, therefore pressure anomalies, to occur at the standard Holley bowl vent locations.

Locating the vent entrance in the hat entrance duct puts it where the flow direction is more uniform than inside the hat. Orienting the vent entrance to face directly into the flow maximizes the effect of increasing bowl pressure as air flow velocity increases. In some applications this is desirable, others maybe not.

Fri Feb 13, 2015 2:45 am
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