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Discussion Starter #1
Factory specs are for few degrees ATDC which I assume was for emissions reasons. What is a good setting for real world performance using good premium gas (93+ octane)?
 

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71 Berlina 74 GTV 17 Giulia Q4
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Maximum advance is the critical setting and should be set there. Rev the motor to 3500 rpm and set the pointer at the M mark on the crank pulley and let the idle advance fall where it may. This goes for the stock Marelli or any of the aftermarket distributors available. If you have a dial back timing light set it to 33- 34 degrees and use the P, tdc mark to line up with the pointer at 3500 rpm. Hope that helps.
 

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The problem is that if his distributor has a long advance curve and he sets the max to 34 degrees then his advance at idle will be too low resulting in poor pick-up. I think that 36 to 38 degrees at 5000 rpm may be more appropriate. Some distributor curves do not give full advance at 3500 rpm so it is better to set the max advance at 5000 unless you know for sure that it is all in at 3500.

Edit: Shankle recommended 36 to 38 degrees at 5000 rpm for modified Marelli distributors on 1750 & 2L motors.
 

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71 Berlina 74 GTV 17 Giulia Q4
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I'll go along with that. Max advance does vary, main thing is set it at max and let the idle fall where it may. Rev it until it doesn't advance any more and set to the M mark. If you have a dial back is when the actual numbers come into play.
 

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Discussion Starter #5
The problem is that if his distributor has a long advance curve and he sets the max to 34 degrees then his advance at idle will be too low resulting in poor pick-up. I think that 36 to 38 degrees at 5000 rpm may be more appropriate. Some distributor curves do not give full advance at 3500 rpm so it is better to set the max advance at 5000 unless you know for sure that it is all in at 3500.

Edit: Shankle recommended 36 to 38 degrees at 5000 rpm for modified Marelli distributors on 1750 & 2L motors.
Makes sense. Have the stock Marelli electronic unit. I'll have that total checked ASAP.
 

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Your distributor will have a model number on the base. If you post that number then I will look it up for you.
 

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71 Berlina 74 GTV 17 Giulia Q4
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If his distributor is working correctly and is stock it has the long curve to allow for the ATDC idle timing. Any advance to a BTDC idle will push the max into dangerous territory. So the correct answer to the original question is there isn't anything to be gained by advancing the timing and it could damage the motor. That is why there are recurved stock s103b's and aftermarket distributors.
 

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What is "dangerous territory"? I have run 39 to 40 with Motronic pistons with no problems. The stock timing for 80/81 Spiders is 38/42 at 4500 rpm.
 

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The advance range on a stock Marelli S 103 B as fitted to the 1972 cars is 34-38 degrees. Stock ignition timing is 5-7 degrees ATDC at idle and 27-33 degrees BTDC at 5000 RPM.
 

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any of the aftermarket distributors

Maximum advance is the critical setting and should be set there. Rev the motor to 3500 rpm and set the pointer at the M mark on the crank pulley and let the idle advance fall where it may. This goes for the stock Marelli or any of the aftermarket distributors available. If you have a dial back timing light set it to 33- 34 degrees and use the P, tdc mark to line up with the pointer at 3500 rpm. Hope that helps.
Any and all electronic/pointless distributors?
 

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71 Berlina 74 GTV 17 Giulia Q4
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Whatever rpm the particular distributor reaches max advance is where the motor should be reved to. You can generally hear a motor ping which is dangerous territory. Problem is detonation is sometimes only apparent when the motor is disassembled because of massive blowby and scuffed piston skirts and busted ring lands are discovered.
 
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