?71 B20B tuning stuff

So now that I have about 2,000 miles on the 142 since the cam swap, I?d like to tweak some stuff for better drive-ability and power. At the moment, the car ?climbs on? hard at 3000rpm and pulls hard to 6k. I use 93 octane exclusively and timing is set at 11deg btdc. Vacuum retard is still connected, but I plan on plugging the line. Valves are set at .016 and I have stock HIF6?s with the secondary butterflies removed. D cam with aluminum timing set.

Where should I set timing? I?ve seen as much as 17 at idle.
Should I make the points gap slightly smaller/larger to improve high rpm ignition?
Any tricks I?m unaware of?

My general rule of thumb on a B20 is to advance the timing until you get an occasional bit of pinging (usually under part throttle) and then back it off slightly. They tend to like as much advance as the engine setup and fuel octane can handle. I don't think it's possible to advance off the front end of the timing curve with that combustion chamber design.

I took the points off mine a LOOONG time ago, using a Crane optical system now. Well worth it because it's less sensitive to shaft wobble (TWSS) and you don't have to gap points or set timing every 5k miles anymore.

JohnMc said:

My general rule of thumb on a B20 is to advance the timing until you get an occasional bit of pinging (usually under part throttle) and then back it off slightly. They tend to like as much advance as the engine setup and fuel octane can handle. I don't think it's possible to advance off the front end of the timing curve with that combustion chamber design.

I took the points off mine a LOOONG time ago, using a Crane optical system now. Well worth it because it's less sensitive to shaft wobble (TWSS) and you don't have to gap points or set timing every 5k miles anymore.

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Where did you get your crane setup? Just a generic 4cyl unit? I like Pertronix but my history with them scares me.

I bought mine well used on eBay. It's so old it says 'Allison' on it. It's been on the PV for probably 15+ years at this point without ever needing the slightest bit of attention paid to it. If I ever bother to hook a timing light up to it, it's right where it was last time.

I did add an MSD box and a Blaster coil a few years ago, which made a noticeable improvement in starting and low RPM use.

No clue on what to do with points gap/dwell and high RPM use. I do know that high rpm weakness is what drove me to replace the stock points and firewall mounted original coil on mine all those years ago. It just wouldn't pull cleanly at higher RPMs. It had a sort of wavering weak feel to it. I thought it was fuel related for a while. Then I was looking at the sparks put out by the decades old original coil and ignition system - wispy thin faint blue sparks. zip, zip, zaip. I replaced it with the Crane system (which I think boosts the voltage some?) and an old square Mallory coil and ZAP, ZAP, ZAP I had big fat red sparks. And that high rpm weakness went away.

EDIT : And yeah, just a generic setup. The kits come with a variety of optical shutter wheels that slide onto the distributor shaft. There's nothing unusal about the Bosch distributors that Volvo used back then. You just need to pay some attention to the sensor pickup and where it's firing the coil - to make sure the rotor is pointed close enough to the correct contact on the cap when the ignition advance is all the way advanced. I think my first attempt was pretty good at lower RPMs, but when revved up, it would start jumping forward to the next contact. Lol.

JohnMc said:

EDIT : And yeah, just a generic setup. The kits come with a variety of optical shutter wheels that slide onto the distributor shaft. There's nothing unusal about the Bosch distributors that Volvo used back then. You just need to pay some attention to the sensor pickup and where it's firing the coil - to make sure the rotor is pointed close enough to the correct contact on the cap when the ignition advance is all the way advanced. I think my first attempt was pretty good at lower RPMs, but when revved up, it would start jumping forward to the next contact. Lol.

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I figured. Once I posted I remembered I'm using VW points, rotor, and cap so obviously they have a wheel for it.