Re: solved! shankle weber conversion (+ ignition questions)

[bearbvd@xxxxxxxxxxxxxx (Greg Hermann)]

At 11:52 AM 7/28/03, Todd Schinell wrote:

In effect, you have slowed down the idle by retarding the timing at low
engine speeds. This retarded timing is what is causing the stumble--and, of
course, also it is killing your throttle response.

No doubt the dizzy needs to be put right, but the stock curve is hardly
ideal. If you have the squish style pistons, something around 150 BTDC at
idle going to 340 at high rpm is in the ballpark. If it won't idle down to
800 rpm with the advance at 15 BTDC at idle, time to figure out why the
carbs aren't closing their butterflies tightly !!

Greg

>Thanx to everyone who suggested solutions to this problem.  It was in fact
>the distributor advance weights not fully retracting at idle.  My kludgy fix
>was to simply bend the ends of the springs that wrap around the posts back a
>bit to make the springs stronger.  Now my idle returns back to 1000 right
>away then settles fairly quickly down to 750 which is much better than it
>was (before it would linger around 2000 to 1500 and take about 30 seconds to
>finally drop).  I attribute the remaining 1000->750 drop to sticky throttle
>shafts on the webers, but it's something i can live with for now.  The main
>problem was definitely weak springs.  The only thing I don't know now is,
>where do I get some proper dist advance springs?  I doubt the ones in there
>were stock, one had round tips that barely fit around the posts and the
>other had square tips.
>
>Now that I've bent the tips back a bit and my idle is worlds better, the
>engine's a little more stumbly or surging until about 2000 when it takes off
>like a rocket.  After 2000 it feels stronger than usual.  The
>points/plugs/condenser/etc are all brand new and adjusted carefully, the
>carbs are in sync and jetted normally (50F8/etc..)  I had adjusted the
>timing with the M mark at 5000rpms with a light.
>
>All this makes me question the effectiveness of the stock marelli points
>ignition.  What are my options for a better solution.  I suppose the systems
>centerline are selling would be a good option, but they are molto expensive.
>What is needed from the 80's spiders with electronic ignition to upgrade my
>car?  I know there's the bosch distributor and the silver ignition box and
>associated wiring, but what else?  Is the MSD a much better choice instead?
>I'm leery of the MSD because it still relies on my crummy old marelli
>distributor and advance system which is causing my problems in the first
>place.  What's the story with Marelliplex? There's also Crane and the
>optical trigger, although having just installed one in an Austin Healey
>leaves me a little wanting with the tangible improvement, and the brackets
>holding the optical trigger seem very cobbled up instead of engineered.
>Perhaps my best option is an MSD with some carefully inspected springs for
>the advance weights... What is everyone else's experience?  Proper ignition
>is so important to the running of the engine I don't want to sell it short.
>___
> /<>/>/>
>77 spider
>
>----- Original Message -----
>From: "Todd Schinell" <alfatodd@domain.elided>
>To: <alfa@domain.elided>
>Sent: Thursday, July 10, 2003 12:34 PM
>Subject: shankle weber conversion behavior
>
>
>> I bought my 77 spider with a shankle weber conversion and euro style
>cannister
>> airbox and I can never seem to get it to idle properly, or rather,
>*return* to
>> idle after it's warmed up and driven.  After a long time, maybe like 20-30
>> seconds, it'll finally drop back down to a proper idle speed.  It likes to
>> linger around 1500-2000 rpms for too long.  The carbs have the usual
>"factory"
>> jetting for a 2L, the throttle plates are in sync, and the idle screws
>have
>> all been carefully adjusted.  It does idle fantastically *once* it finally
>> decides to.  Basically the only way for me to get my engine down to idle
>> speeds promptly once warmed up, is to retard my ignition timing.  I know
>isn't
>> the right way to do it.  Is this just a characteristic of webers in
>general?
>> or the shankle conversion in general?  Would a proper euro manifold &
>> mounts/etc do this as well?  I have recent regular bosch platinums in
>there
>> and new properly adjusted points, the ignition is basically up to par.
>>
>> My ultimate goal is to convert back to spica, however that is a long way
>off
>> due to money and lots of missing parts (pretty much all of them)
>> ____
>>   /<>/>/>
>> 77 spider refuses to sit "idle" :)
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