[Mgs] Dynamic timing 74 B

[Max Heim]

Yeah, check the butterflies. After a lot of fiddling I finally pinned that
down as the cause of my persistent high idle. One of the discs was just
slightly off-center, and not closing all the way. Compounding this, the
shaft was slightly flared out at the end of the slot and sticking in the
bushing. Both carbs showed this last symptom to some extent.


--

Max Heim
'66 MGB GHN3L76149
If you're near Menlo Park, CA,
it's the primer red one with chrome wires



on 7/4/13 8:32 AM, PaulHunt73 at paulhunt73 at virginmedia.com wrote:

> Consensus?  You must be joking!
> 
> You are right to get the ignition right before tackling the carbs, but that
> really relates to fixing any defects causing misfiring which can confuse the
> issue when you are trying to setup the carbs.  A North American 74 (chrome
> bumper) had an 18V 672/673 engine with a 25D4 41491 distributor.  That had a
> static timing of 6 degrees BTDC and a dynamic of 11 degrees at 1500rpm.  So
> if your idle is 1400 to 1500 rpm that's half the job done for you :o)
> 
> There can be a number of things that can cause a high idle as well as worn
> throttle spindles and bushings, such as incorrectly set linkages such that
> one butterfly completely closed is holding the other open, a butterfly not
> fully seating in the throat, poppet valves in a butterfly not fully closed,
> insufficient free play in the throttle cable holding the butterflies open,
> as well as incorrectly set idle and fast idle screws.  One thing that
> *can't* cause it despite many claims to the contrary is a vacuum leak.  A
> vacuum leak *will* cause a high idle for a given throttle opening, but an
> engine cannot run on air alone, and you should always be able to stall an
> engine with the idle screws - *if* everything else above is correct - even
> if there is a vacuum leak.
> 
> PaulH.
> 
> ----- Original Message -----
>> ... What is the consensus of what the dynamic timing should be set with
>> vacuum advance disconnected and plugged off??