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On the throttle plates in the HS4's on my 71 B there is a hole on the lower half that is filled with a silverish goop on the plate in the front carb and its open on the rear carb. Am I correct that both the front and rear carbs should have the hole filled, and if so what do i fill it with? It half looks like a solder to me but wasnt sure. Thanks
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su hs4 throttle plate hole?
- Thread starter gm9142l
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Bob Claffie
Jedi Knight
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Sounds like somebody did away with the small valves that should be on the throttle plate. Why one is plugged and the other is open baffles me. Given the alternative I would get new throttle plates complete with the valves. (I have them on my "B"). Bob
[ 04-18-2003: Message edited by: Bob Claffie ]</p>
[ 04-18-2003: Message edited by: Bob Claffie ]</p>
A
aerog
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The "valve" is present on the HIF carb plates and is intended to improve fuel burn in overrun conditions and thereby also acting as an emissions control device.
Unless I'm very much mistaken, the HS4 carbs don't have the valve and should have a solid throttle plate, although the SU parts manual shows what appears to be an HIF plate with a filled-in hole. [the SU book points out that the valved plates were one of the changes between early carbs at the HIFs]
In any event, I would think you'd want both of them filled. Under certain conditions the valved plates open, creating what you have in the "open" throttle plate - but the valves are springloaded to close in other conditions, something your plate isn't capable of doing.
I don't recall reading anything that recommends a setup like you have, so I'd imagine your best bet would be to order a new HS4 throttle plate or fill the hole in yours with silver-solder. Since you've got to take it apart anyway, it probably would be just as easy to order a new one.
[ 04-19-2003: Message edited by: aerog ]</p>
Unless I'm very much mistaken, the HS4 carbs don't have the valve and should have a solid throttle plate, although the SU parts manual shows what appears to be an HIF plate with a filled-in hole. [the SU book points out that the valved plates were one of the changes between early carbs at the HIFs]
In any event, I would think you'd want both of them filled. Under certain conditions the valved plates open, creating what you have in the "open" throttle plate - but the valves are springloaded to close in other conditions, something your plate isn't capable of doing.
I don't recall reading anything that recommends a setup like you have, so I'd imagine your best bet would be to order a new HS4 throttle plate or fill the hole in yours with silver-solder. Since you've got to take it apart anyway, it probably would be just as easy to order a new one.
[ 04-19-2003: Message edited by: aerog ]</p>
after searching in some manuals and looking up the AUD number (405F) in the moss cat, it seems a PO decided to do away with the over run valves. While starting the car to get all the linkage and choke properly adjusted and the carbs synced I had a couple big back fires, Im guessing those back fires where enough to put a hole in the solder. Pulled the carbs off and am patching the hole with new solder. Well see how it works. Thanks guys
Wade Keene
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HS4s from about '70 on had the overrun valves/poppet valves/whatever you want to call them. All HIF4 and HS4 butterflys are totally interchangeable so you can also just get a pair of new (or used) solid butterflys.