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Marelli or Bosch distributor for the 69 GTv?

1989 Views 4 Replies 4 Participants Last post by  genericwood
The distributor on the 1750 engine of my US model 1969 GTV seems to be a Bosch unit. However the ALFA parts manual shows that the Marelli should have been fitted. What are the pros/cons between the two...if any? (My objective for the car is to restore it to as close to it's original factory configuration as possible and so I'm leaning towards going with the Marelli...unless there is good technical reason for not doing so).
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The parts book is correct. The US version 1750s were fitted with the Marelli S103B distributor. The Euro cars were fitted with the Bosch 041 or 044. Both will work equally well. However, the Bosch units have a more aggressive advance curve than the Marelli and as such, may return better drivability, performance and fuel mileage.
Bosch advance curve.
Marelli advance curve.
Back in the day, having the Bosch unit on my Canadian GTV meant I could get the points and condensor from any VW Beetle shop. Really handy when there were only a few Alfas in town ;)
Thanks Jim, it now seems likely that the PO or his mechanic were trying to tweek the engine with the distributor change. However they may have gone a little too hot with the advance resulting in some pretty serious detonation.....ever seen it this bad? This is the number 2 piston, the others didn't show any detonation effects at all.

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This is the distributor that came with the car. Makes me wonder if the Marelli is the safer way to go?

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Either distributor will work just fine. No matter which way you go, don't set the timing at idle, set it at revs at full advance. That way you won't get detonation. If only one cylinder was detonating, it probably wasn't a result of timing alone. I'm guessing that cylinder went very lean for some reason?

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