Carburetters ?

D

DAV8

Member
Hi All,
I'm not sure if I'm in the right area here so I hope somebody out there will be able to advise/help. Recently I have been out in my 3500 auto (1971) and have had the following situations, the car generally seems to run okay but if I stop for about an hour or so and then restart the car it seems a bit uneven, put it into drive or reverse and it cuts out and then can take a bit of starting with or without the choke, it will fire up after 2 or 3 attempts but runs uneven, rev it up a bit and then seems okay, when braking on the approach to a junction or traffic lights especially going down hill it often almost cuts out (as if mis-firing) could this be a problem with the carbs ?, the carbs are the HS6 type (float chambers on the front). Normal driving the car runs quite well i.e it pulls okay with no hesitation etc. Work I have done in the last few weeks includes:- renewing all the plug leads, cleaned all the spark plugs (they all looked in good condition - correct colour etc) hydraulic dampers in the carbs are correct level ( I've always used 20/50 engine oil) I have fitted a "Boyer Bransdon" electronic ignition system many years ago (this uses the points as a switch and therefore there is very little current going through them) this has never given any trouble.
Hope somebody can help.
DAV8
Dave
 
Hi Dave,

Carburettors are certainly a possibility. When did you last overhaul them? What about your air filters, how many Miles (or years) have you travelled since they were last replaced?

Basically unless something is totally obvious, it will be down to a methodical process of elimination.

Ron.
 
Hi Ron,
Thanks for your reply. The last time the carburetters were overhauled was when the car was restored between 1998 and 2002, so they were probably done about 12 years ago, the air filters were changed about 10 years ago but I regulary give them a clean out, (there's never much dirt in them) in that time I have travelled about 15,000 miles. I wondered if perhaps one of the floats had sprung a leak and sank ?
Best Regards DAV8
Dave
 
Hi Dav8 .
Sounds like a good inspection of the carb linkages and a session of balancing and mixture setting would be a good place to start .
Is the pipe from carb tower to rad clear of blockages ? If not undue heat can build up there and vaporise fuel / make the carbs run hotter than ideal . Especially after it's run up to temp then subjected to heat sink when it,s stood :!:
Just some things i would be looking at if it were mine :wink:
 
Hi Dave,

I have never dismantled HS6 carburettors, so I can't say if a leaking float is a possibility. I know that with HIF6 carburettors it certainly is, so if in doubt, pull them out and take a look.

Paper element air filters should ideally be changed every 12 months regardless of how little the car is used, which could actually be part of the problem, insuffucient use. Mechanical items always work best along with delivering the greatest reliability when used regularly.

At what speed does your engine idle at when in drive, say after a run?

Ron.
 
Hi Stina & Ron,
Thanks for the info, the linkages look fine, I regulary check and clean/lubricate them, as for balancing etc, I think I will have to get a chap who does this (Jim Parkes in Sheffield).
Ron, the idle speed when the engine is hot is around 850/900 RPM with the auto box in neutral.
Thanks again DAV8
Dave
 
A leaking float on an hs6 can happen. It's only 3 screws on the hs6 to have a look because they have the separate float chamber on the side...

Rich
 
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