This may seem like a dumb question , but what are the timing specs for B20f engine? I have the sticker under the hood, a chilton's manual, and they both suggest timing adjustments differently. Basically the volvo spec sticker under the hood says "10° adv@700-900rpm-->No Vac". I set the timing to this and the car is sluggish/hesitant/rough idle. what do I do now.... I have about fifteen years under the shade-tree working on enigines of all sorts.. What I need to know is:
1.what is the max adv°?
2.How much adv does the the centerfugial weights adv and @ what rpm?
3.Why the H$!! does the Vac Retard the timing (noteworthy-->the car runs better w/o vac connected)?
My thought was to set the timing to "MAX adv @ 2000+ rpms" set the idle and call it happiness. (note: my crank pulley has deg° marked to 40°)
History with the ignition all together:
-Parts replaced in last 5 months: -Distributor(Bosch-New Complete) -plugs and wires -ignition harness (up to key)
-Parts Mods: Ballast resistor, Accel Coil, Crane XR_700 Ign_Module

Any help with spec's would be happiness. ---Eric/Portland-- 73/145/b20f

Thank you George, And all who responded with helpfull advice.
I assess from reading these responces that basically every B20F motor has a "sweet" spot in timing. I took George's advice and set to timing-by-sound after a brief timing-light setting. I took my tools with for a drive and adv/ret the timing using minor detents and frequent stops to come into the "sweet". Mine turned out to accelerate hard and idle smoothly at 16°.
Thanks all for the advice ----Eric Rossman--73/145--

Heck...if you're a shade tree mechanic, you should know better than to have a timing light. Just throw it away and time it by ear. Well...maybe keep it around for your V-8 cars, but no need for it with a 4 banger. After about 6 years of Volvo ownership, I finally got a light...and every time I set it exactly to spec, it don't run right and I just pull over on the road and set it by ear until it runs right and doesn't ping. Ususally takes a couple days to get it just right.

The proper spec also depends (a little) on your altitude. Or so I've heard. But here at about 5000 feet above sea level, I've always been told that 10-12 degrees at idle (vaccuum disconnected) was proper. But mine has always run best at about 14-16 degrees. Some of my cars have knocked though, and had to be backed off a bit.

Furthurmore, with my older cars (pre F.I.) that had more of a knock&ping problem, I would set the timing differently in summer than in winter. No...that ain't right, but the car worked best that way.

-Matt

I have been removing the vacuum retard system for years with good results. It was designed to lower peak combustion temperatures to reduce NOx formation, but it also reduced fuel mileage, power, and throttle response. Disconnect it and set the initial timing at 10 degrees BTDC. Max advance on these engines should be about 34-36 degrees, at something around 3500 RPM depending on the distributor curve. Detonation at that RPM is usually inaudible, and one should limit total advance as a result to the factory amount.
Try it and see what happens - the low compression B20F should respond quite well.

I've received a LOT of flak over this but it seems to work well for me
so I keep on doin' it.
If it's got vacuum, leave it connected. If it doesn't, no problem.
Set the timing at about 21-24° BTDC at idle. Drive it some, especially
at moderate or low speed under heavy load (i.e. up a hill) after it is
warmed up good. If it pings, knocks or kicks back against the starter,
back the timing off a few degrees at a time until it is tractable.

This may not satisfy emission authorities but as I say, it works OK for me.
GFD III

Total advance may go over 40°. If it runs well and doesn't ping or knock,
no problem.
--
George Downs Bartlesville, Oklahoma

I'm with George on this one.
My last B-20F was happy for years at 18 BTDC, vac. disconnected, @1500 RPM, with 89 octane gas.
I discovered this just as he says.
I have no trouble hearing pinging, myself.

Err, I don't want to start a pissing contest on this, but 18 degrees at 1500 RPM is hardly 21-25 at Idle.


Regards



Pete

My point is that I got to where I ran by exactly the method described by George. Where I started was not where I finished.
After ~12 years the motor finally started to burn too much oil; there were no signs of detonation when I tore it down.

There are very good reasons NOT to do this. At idle with this much advance you will get decent idle. Try it on an engine some time with a hot cam in it. At the proper setting 12-15 degrees maximum it'll idle like a pig. Advance it to 25 and it'll idle beautifully.

However at idle you only have partial cylinder filling, nail the throttle to pull away hard and it will pink under load, you just can't hear it doing so because of all the other stuff going on. If you want this much advance idle you need mappable ignition, with a map to back it off to safe levels on hard acceleration. Or regular engine rebuilds. Equally advancing much above 39-40 degrees total is asking for trouble.

Regards


Pete