needle/seat

[Clem Z.]

several times i have posted about using a "windowed" needle/seat used on Q jet carbs so here is a picture. high performance corvette engines need this type of needle/seat to allow enought fuel into the carb at WOT

[John D.]

Re: needle/seat

Clem, The windowed N&S is quite common as you know. The old 57 to 65 used that type of seat. Most carbs in the old days used it also.
That's one strange looking needle though. Your pic isn't too clear with my little monitor but it looks like the viton needle has a blunt end.
A lot of the windowed seats also have cross drilled holes in them.
When that viton needle and seat first came out it was called a Vitron or Vitren needle. JD

[Clem Z.]

Re: needle/seat

Clem, The windowed N&S is quite common as you know. The old 57 to 65 used that type of seat. Most carbs in the old days used it also.
That's one strange looking needle though. Your pic isn't too clear with my little monitor but it looks like the viton needle has a blunt end.
A lot of the windowed seats also have cross drilled holes in them.
When that viton needle and seat first came out it was called a Vitron or Vitren needle. JD

the problem now days is that carb rebuild kits do not come with them and i have to machine them for more flow. since Q jet carbs have only 1 needle/seat to pass the fuel the fuel has to get out without having to go up past the needle as that is a BIG restriction to the flow. the blunt end allows more fuel to pass as it does not stick down into the needle seat opening restricting then flow.

[Stuart F.]

Re: needle/seat

Another alternative are the Tomco inlet valves. These are still available somewhere as I got a set in a recent rebuild kit for an AFB that I purchased from Ecklers. They use a Viton disc which rides between a seat and a plunger and are cross drilled at the disc position. My only concern when I received them was that the openings in the seat portion are above the gasket surface and the gasket only has a few small holes in it for venting the bowl to the top plate vents. I modified the gasket so that it only seals at the sealing edges/surfaces and is otherwise open. I also run the floats about a 1/16" lower (5/16" vs. 1/4") to lessen the chance for sloshing and I figured the increased flow would not need as much fuel in the bowl at WOT.

I have one of these that I purchased many years ago for a QJ along with the literature. That was how I was able to identify them when I received the kit.

Stu Fox