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71 Berlina 74 GTV 17 Giulia Q4
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Discussion Starter #1
In searching for information I've come across issues with motronic pistons breaking ring lands from several different and unrelated sources. In addition I've also found there appears to be an issue with certain timing lights giving inaccurate timing with MSD units specifically with digital dial back lights and some other traditional lights. I have motronic pistons and a msd and have noticed that when I set my timing to an INDICATED 33 or more degrees I have a high frequency vibration tied to rpm s best felt in the gear lever. I can retard the timing to an indicated 32 -30 degrees and the vibration goes away and the motor still runs like stink according to my redneck dyno. It also revs to 7200 with more gusto when set to the lower indicated numbers. I was wondering if anyone else has experienced anything similar? Comments, suggestions? Much gras!
 

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I would make an M mark on the pulley at the max advance that you desire then use the timing light set at zero or a plain timing light with no adjustment.
I have an MSD6AL and a HF adjustable light and I have had no problems.
 

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I've also heard this about MSD's. I wonder if there's variation imposed by the MSD firing over multiple crankshaft degrees. MSD told me that the 6A when set for a 4 cylinder engine fires over 10 crankshaft degrees. If you have a fast advance curve that's all in by 3000 or 3500, this could still put you in the MSD multiple firing mode. That's one reason I installed a degreed crankshaft pulley from Classic Alfa.
 

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71 Berlina 74 GTV 17 Giulia Q4
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Discussion Starter #4
I also have a hf dial back in addition to my trusty 45+ year old Craftsman light. Both give rock steady illumination of the pulley marks when used on my spare motor on the test stand that has pertronix igniter and coil ignition. I see ghost marks when used on the GTV/msd, blaster2 coil, and magnacore plug wires. I suspect both lights are picking up stray signals. I'd get a degreed crank pulley if I could find one with 2 grooves.
 

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In his book JimK shows a degreed stock pulley, made using a "divider" and vertical mill. If you can do that on your lathe, you'd have an instant cottage industry.
 

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Richard Jemison
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Timing

I have motronic pistons and a msd and have noticed that when I set my timing to an INDICATED 33 or more degrees I have a high frequency vibration tied to rpm s best felt in the gear lever. I can retard the timing to an indicated 32 -30 degrees and the vibration goes away and the motor still runs like stink according to my redneck dyno. It also revs to 7200 with more gusto when set to the lower indicated numbers. I was wondering if anyone else has experienced anything similar? Comments, suggestions? Much gras!
That is simply indicating too much ignition advance !

Commonly programable advance units allow matching correct advance (in degress based on RPMs. However common practice is to set max timing at what works with the lowest advance required to get max output on the dyno.
Reducing advance under load is nothing new, vaccuum advance distributors that retard timing under load ( low to no manifold pressures) solves lots of issues.

Short fast ignition ramp advance rate units can cause issues on street cars, since ign advance rates can be in excess of optimal other than at high RPM. Fine for race engines, but not street use.
 

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Premium Member
71 Berlina 74 GTV 17 Giulia Q4
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6,471 Posts
Discussion Starter #7
In excess of optimal advance at max load, max torque which makes the correct timing advance at around 4000 rpm and zero or close to it manifold pressure ie., WOT all the more important. Seeing through the noise is essential!
I wouldn't mind at all setting up a cottage industry for friends but as far as being able to compete with a programmed CnC machine for profit I wouldn't stand a chance:) Although I did turn a valve guide seal install tool yesterday in about 5 minutes! I wised up an boiled them in water before putting them on and they were the easiest ones I've ever done.
 
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