I have just re-kitted the HS8s in our XJ6 hoping to improve idle. New shafts included. Disappointed that little or no improvement in idle quality (not been out on the road as yet). Found this article whch counsels the remove or sealing up of the overrun valves: suggests the springs weaken with age and upset idle due high vacuum. Anyone made this change on their car? Paul
https://www.calverst.com/technical-info/su-carbs-poor-idle-quality/
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First of all, Paul - the xk engines’ idle is seldom rock steady. And trying to get there is an uphill battle; so many factors are involved that they are difficult to identify and correct.
If you do have the overrun valves on the carbs, to be identified as mentioned in the article - they are very unlikely to be involved in idle. However, if they do open at, or below, normal idle vacuum it is almost impossible to adjust carbs properly…
Fitting overrun valves when not originally fitted to improve idle is a waste of time…
Frank
xj6 85 Sov Europe (UK/NZ)
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Thanks for the response, Frank. Our car does have the overrun valves (1972) - just looking for excuses perhaps! In any case the car is back together now - valves and all. Paul
Paul
we spent a lot of time on my HS8 carbs , in the end the carbs where balanced well , ticked over quite well and revved up sweet as anything .
Soon as we took it out on the road it was soon clear things where not right ,
Had to adjust the mixture screws down a bit .
So when you take your car out on the road test , take a screwdriver , you may need it !
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Carb adjustments are sort of trial and error, Ian - a bit of fine tuning is to be expected…
Frank
xj6 85 Sov Europe (UK/NZ)
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