Adjust-A-Jet

[Mike Switzer]

Does anyone have any experience using Percy's Adjust-A-Jet for the Holley carbs in an aviation application?

http://www.taylorvertex.com/Products/index.cgi/percyProducts?ID=160

The reviews on the hot rod forums seem mixed, and for a street car I tend to agree, find the correct jets & leave it alone, but it looks like it may work for aviation purposes.

[martymayes]

looks like it may work for aviation purposes.

How much is it? I couldn't get it to show a price, even when I clicked "buy"

I don't see much benefit, but if they ever come out with an adjust-a-power valve, I'm there.

[Mike Switzer]

Summit sells it for just under $80 - supposedly you can change the mixture while operating, so my interest is being able to change the mixture with altitude like you can on an aircraft carb. I got looking for something like this because I remembered reading about someone using a Ford engine in a homebuilt that was using a "special" Holley 2 barrel that allowed mixture adjustment - this was all I could find, evidently this (or something similar) has been around since the 70s & Holley did sell something identical to this for a while as an option.

[martymayes]

Summit sells it for just under $80 - supposedly you can change the mixture while operating, so my interest is being able to change the mixture with altitude like you can on an aircraft carb. I got looking for something like this because I remembered reading about someone using a Ford engine in a homebuilt that was using a "special" Holley 2 barrel that allowed mixture adjustment - this was all I could find, evidently this (or something similar) has been around since the 70s & Holley did sell something identical to this for a while as an option.

From what I read it requires turning a screw with a screwdriver, the number of turns approximately equals a corresponding jet size and changing the main metering jet on a Holley carb isn't quite the same as adjusting the fuel air mixture like an aircraft carburetor.

David Blanton did a Ford engine conversion (actually a couple Ford engine conversions) and from what I recall, he specified installing a Holley carburetor model that had automatic altitude compensation for up to ~5000 ft. Not sure if the compensation was electronic or mechanical but it didn't require any input from the pilot. I don't recall what model Holley carburetor he used but I do remember seeing the 172(175?) airframe with Ford V6 installed at Oshkosh one year during the '80's. I'll have to dig around when I get back home cause I'm pretty sure I have a SA article about the conversion and we might be talking about the same article. Davy Blanton used that same engine in his homebuilt V6 Sport Racer. That airplane BTW occasionally shows up for sale.

[Mike Switzer]

I think there may have been a couple versions of this setup - a couple of the posts I found in the hot rod forums sounded like they were talking about adjusting something while they were driving.