Even thought I’m elated that the engine fires up and idles, there is some room for improvement. If I try to increase the revs too quickly, the engine wants to die.
Looks like there’s a general 3 step approach. Stoddard has a handy online Tune-up Specifications page for most of the pertinent numbers:
- Adjust the valves
- Set the points
- Check the timing
Adjust the Valves
Assuming you have the correct sticker on your fan shroud, the numbers are right in front of you. For a 356B Super 90, it’s Intake .006″ and Exhaust .004″. This is reverse of a Normal engine. For a newly rebuilt engine, The Maestro Harry Pellow recommends erring on the loose side. So we set everything to .007″ for the initial runnings.
Set the Points
Not obvious to me when setting the points was the oblong screw head that allows travel back and forth. Heidi and Franny’s Garage ladies have a video series on 356 tune-up. Their Electrical Tune-up! Points, Plugs, Timing segment is way more informative than any series of photos I can offer. For reference, our point gap on the Super 90 is meant to be .016″.
Check the Timing
Timing is meant to be checked at some number of degrees offset from top dead center. Once again, the Super 90 is slightly different with a spec of 3 BTDC (Normals are 5). That’s three degrees before top dead center (BTDC).
We’ve got our mark on the pulley for OT. Presumably short for Oben (top). So how far which way is three degrees before top dead center?
Inspired by posts regarding Timing and pulley question as well as help in setting ignition timing I believe I’ve sorted it out.
We are essentially measuring length in an arc. So if high school math and Google taught us anything, we should be able to take our desired number of degrees as a fraction multiplied by the circumference of our pulley.
- Our pulley is 145mm in diameter
- Circumference is diameter * Pi (3.14159) = 455.5mm
- 3-degrees as a fraction of a circle (360-degrees) = .0083
- Length of 3 degrees on circumference of our pulley would be 3.78mm
Since the engine rotates clockwise when viewed from the pulley side (i.e. back) of the car, setting “before” means a mark to the right of our factory OT mark.
So I’ll use a flexible tape to measure on the curve and make a little paint pen mark just shy of 4mm to the right of the factory OT mark. We’ll take a run at setting our timing from there.
I’m only looking at static timing at the moment, which is checking for contact between the points in the distributor. Well described in the Registry Tech Article: Ignition Tuning Procedure, and demonstrated in Heidi & Franny video.
One small clarification is references to continuity testers. In my very limited experience, a continuity tester has its own power (i.e. battery) and will light on closed circuit. I think what you really need is volt or ohm meter which will measure output, as there will be power supplied from the car battery with the ignition on. Old school analog tachometer (RPM) / Volt / Dwell meters seem to be out of production. I don’t know the quality or accuracy, but there are decent reviews on a digital unit that has alligator clips so we’ll give it a go. I’d be interested to know the idle RPM and a surprising number of volt meters don’t have clips, which is a PITA.
We will run with the above and observe our results. Then we will determine if we need to adjust carbs. That will be another project in itself I think.
P.S. Plug gap I guess could be included in here too. We did this quite a while back in the engine assembly. .024 – .028″ is the correct gap.
