Just curious on this. Some seats have the two windows in them, others do not. I have been told that the windowed seats are better because they smooth out flow into the bowl, but the Roe book also says they don't flow as well....not sure why that would be, seems to me you have three openings instead of one.... Any thoughts?? And best place to purchase (had some GM ones but they are all discontinued now)?? Later Tim
I was just thumbing thru the Roe book the other day. I noticed the same thing about the windowed vs. non-windowed seats. He said that the non-windowed seats flowed better. Makes sense....no extra open areas for a restriction. If you can't find them at your local parts store, you might try some of the bigger carb rebuild houses.
I believe his contention was, that with the non-windowed seat - it acts like a straight tube and doesn't try to exit at a 90* angle. The best flowing elbows are radiused, not a 90* angle. A straight section should flow even better. Best analogy I can think of, is the EGR/crossover 'windows' in the center ports. When they are stock, those 'windowed' ports don't flow as good as the other regular ports do. When the 'windows' are filled - they flow as good as the other ports. That's how I took it to mean.....hopefully, I didn't misread anything.
Good points but the seat also has the straight through passage... Still seems odd to me. The inlet fuel is under pump pressure, the bowl is at atmosphere, a fluid under pressure exerts that pressure equally in all directions so with the windows you would think the exit area has probably doubled so it should flow more should it not unless you reach the limit of the inlet orifice??? Unless the windows really upset the flow, but they would have to be really bad..... I thought perhaps it was typo....not being a schmuck here, just seems to contradict my experience.... Thanks Tim
My thoughts are that any gas trying to go out the 2 windows, will be turbulent and will possibly get somewhat aerated. I don't know..... I'll defer any further comments to someone that actually knows (an answer for you).
I was just talking to John Osborne and he said the windowed seats do cause some turbulence which can make it hard for the needle to control the flow....interesting.... And yet others have said the windowed seat keeps the fuel from spraying up or vapourizing and following the gasket edge which can cause problems too. So I guess its a trade off....odd thing is, the needle and seat the GSCA always suggested was the gm 7035140 which was windowed. I love F.I.!!!! Later Tim
Edelbrock makes a high flow needle / seat. The entrance diameter is considerably larger than a stock or stock replacement needle/seat... $.02 Dan
yeah its huge though, and with the stage 1 pump might be too much here for our altitude....with larger needle and seats you need less pressure and float height or you'll get flooding and spewing... Later Tim
I have always found the windowed ones with larger hole up the middle. Different varaitions of all of them. from under neath there is long taper short taper, windows are cut like a cube or tapered cut. Like a presure washer nozzle tip. I prefer the long taper bottom with the taper cut windows, bigger the better . I Have one that my secondary needles fit into nicely all the way up halfway. I think some books purposly try to detour you from modifying in a way that burns more wide open throtle. If you are fuel whats the first thing you see when you go straight up to the top of the seat. The flat arm of the float .I have 5 different rochester manuals, only that one your talking about favors the none window.
