Importance of serrated washer AUC1928J on SU carbs

Technical advice Q&A

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PierreW
Posts: 52
Joined: Sun Apr 23, 2023 5:45 am
Location: France
France

#1 Importance of serrated washer AUC1928J on SU carbs

Post by PierreW » Wed Aug 23, 2023 3:43 pm

After struggling for a long time to figure out why fuel was leaking from one of the intakes and the engine was running very often erratically, I noticed that one of the gaskets under nut 5832 was a non-serrated gasket. Why are they "serrated"? To allow, when filling the bowls, air to escape through the overflow tubes. As a result the level rises and the valve controlling the level can close when the bowl is full. If there is not the right gasket (this was the case with me, a bad perfectly circular gasket stuck even around the nut, therefore completely airtight) the air does not escape and the pump continues to fill the carburetor since the JLM9733 needle does not close the fuel supply and in parallel the pressure rises in the bowl and pushes the fuel into the main jet with all the pressure from the pump! A few small strokes of the file in the joint to transform it into "serrated" and ...problem solved!!! I lost a lot of time looking for why I couldn't adjust this engine correctly so if my adventure can clear up some "mysteries" ..... Happy :wink: :bigrin:
Jaguar MK2 1967 since 1980
MGA 1500 roadster 1957 since 1982
Lotus Seven 1963 since 2015
XKE S1 1964 OTS since 2023

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caveman
Posts: 503
Joined: Sun Nov 18, 2007 10:55 am
Great Britain

#2 Re: Importance of serrated washer AUC1928J on SU carbs

Post by caveman » Wed Aug 23, 2023 7:09 pm

Pierre,
Looking at the SNG site, there are two washers under bolt 5832. One, as you correctly indicate, should be serrated.
Image
Steve
1965 S1 4.2 FHC (early)

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Topic author
PierreW
Posts: 52
Joined: Sun Apr 23, 2023 5:45 am
Location: France
France

#3 Re: Importance of serrated washer AUC1928J on SU carbs

Post by PierreW » Wed Aug 23, 2023 8:01 pm

39 is over the banjo
38 MUST be under the banjo!
Thank you for the picture :P
Jaguar MK2 1967 since 1980
MGA 1500 roadster 1957 since 1982
Lotus Seven 1963 since 2015
XKE S1 1964 OTS since 2023

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