[Healeys] SU Dashpot puzzle

[simon.lachlan at alexarevel.plus.com]

Here's one for the technoctats:-

You may have noticed my posts about swapping from two-shouldered to
single-shouldered dashpots. I did it because having two of one and one of
the other was irritating, not because I thought there'd be any changes.

So, I swapped the offending two and that gave me three HD6s, all with one
shoulder.

Car started on the choke, same as normal. Seemingly!

However, doing the garden hose in one ear trick revealed that the rear carb,
always single shouldered, was making less intake hiss than the other
recently added pair. Easily rectified.

 

I took the car out this afternoon. Started fine and ran well. But, if I
eased off, the revs dropped and the engine cut out. Also, there was quite a
lot of popping and f**ting on the overrun.

So, on my return, I gave the front two carbs about half a turn up on the
slow idle screws. This, quite small adjustment really, seemed to cure it and
even to raise the idle rather higher than I like. 

Adjusted down quarter of a turn and all seems well.

Questions:- beyond the obvious - ie that changing dashpots does make a
difference after all - what is going on? Why was there a change?

(Plainly, I swapped needles and springs when I swapped dashpots so I've got
all the same in the carbs..the ones that I had all along).

Any ideas?

Simon

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