850 distributor advance
- Thread starter HazN
- Start date
All my manuals state 10-11º advance across the board, so I don't know that it matters. :hmm:
Where's Jeff Stich when you need him? :dunce:
My Fiat shop manual shows the 903 having a static advance of 0 degrees, and the mechanical advance running to 38 degrees.
The 843 has a mechanical advance of 0 - 28 degrees, but you have to add the 10 degrees static advance for the 100G.002, or 11 degrees for the 100G.000.
The early 100G.002 shows a Vacuum advance of 0-25 degrees, with a 10 degree static advance, the least of any.
My Haynes manual has the 843 distributor numbers:
Marelli
100G.000 S110B
100G.002 S110C
100GB.000 S110BA
100GC.000 S110BA
100GBC.000 S110BAA
I don't have the numbers for the 903 engines and mine is in storage. They came with either Marelli or Ducellier.
If you have a 903 distributor and have set it to 10 degrees static, you will have WAY too much advance.
The best thing to do is get a digital timing light with adjustable advance and dwell measurement. Set it to the max advance you want, 35-38, and set timing at 4000 rpm to zero.
One particular problem I had on my Ducellier was the lobes were worn, so to get the correct dwell I had to close the points down to .012. Make sure to set the dwell before adjusting timing.
The 843 has a mechanical advance of 0 - 28 degrees, but you have to add the 10 degrees static advance for the 100G.002, or 11 degrees for the 100G.000.
The early 100G.002 shows a Vacuum advance of 0-25 degrees, with a 10 degree static advance, the least of any.
My Haynes manual has the 843 distributor numbers:
Marelli
100G.000 S110B
100G.002 S110C
100GB.000 S110BA
100GC.000 S110BA
100GBC.000 S110BAA
I don't have the numbers for the 903 engines and mine is in storage. They came with either Marelli or Ducellier.
If you have a 903 distributor and have set it to 10 degrees static, you will have WAY too much advance.
The best thing to do is get a digital timing light with adjustable advance and dwell measurement. Set it to the max advance you want, 35-38, and set timing at 4000 rpm to zero.
One particular problem I had on my Ducellier was the lobes were worn, so to get the correct dwell I had to close the points down to .012. Make sure to set the dwell before adjusting timing.
HazN
True Classic
My engine's specs.
The block is a 100GB.000. It started life as an 843cc. It has been stroked with a 74mm crank and overbored to 66mm giving a displacement of 1013cc. By my calculations, it's compression is 10.8:1. It has a mild cam. Effectively it is a clone of the Abarth 1000 OT engine. That engine has a static advance of 8° and a total advance of 24°. I just need some basic numbers to have the distributor recurved (if I can find a place that still does that). I read a post from Obert that the 903cc distributor has less advance than the 843cc. I presently have it set to 4° static and it does not ping on pump premium. But the engine runs too warm for my liking. I had more static advance when I mixed 1 gallon Cam 2 to 5 premium. It ran cooler. But that stuff is multo caro.
The block is a 100GB.000. It started life as an 843cc. It has been stroked with a 74mm crank and overbored to 66mm giving a displacement of 1013cc. By my calculations, it's compression is 10.8:1. It has a mild cam. Effectively it is a clone of the Abarth 1000 OT engine. That engine has a static advance of 8° and a total advance of 24°. I just need some basic numbers to have the distributor recurved (if I can find a place that still does that). I read a post from Obert that the 903cc distributor has less advance than the 843cc. I presently have it set to 4° static and it does not ping on pump premium. But the engine runs too warm for my liking. I had more static advance when I mixed 1 gallon Cam 2 to 5 premium. It ran cooler. But that stuff is multo caro.
Old-school timing method
You could always use my highly unscientific method (a relic of my former air-cooled VW days): Rotate the distributor until idle speed is maximized, then drive the car. Advance or retard a bit at a time as needed until it just starts to ping under load, then back off a bit.
But you already knew that.............
You could always use my highly unscientific method (a relic of my former air-cooled VW days): Rotate the distributor until idle speed is maximized, then drive the car. Advance or retard a bit at a time as needed until it just starts to ping under load, then back off a bit.
But you already knew that.............