optical trigger and timing

[ein 6er]

1st ....... happy new year to all and best wishes for the new year!!!!!!!

anybody have the crain xr 700 and the optical trigger?!?

i installed mine to mask a worn dizzy. '67 2.0L carbs, and i've been chasing carb and/or ignition problems. well, i recently got the dizzy rebuilt and i'm working on the timing. i don't have a manual for this engine but from what i understand i'm trying to get the timing close to 35° BTDC @ 6000 rpm.

i understand how turning the dizzy will advance the timing with points. but ........ with the optical trigger ........ what does turning the dizzy do, do you >need< to rotate the dizzy like with points?? there is a lot of adjustment with the optical trigger. would you align the timing marks, (z1, rotor, dizzy #1 mark) and then adjust the optical trigger until you get it to time at 35° BTDC. or .......... can you rotate the flywheel to the 35° mark and then adjust the optical trigger so that it triggers then?!?

i set the timing once before with the optical trigger by rotating the dizzy and then readjusting the trigger, trial and error, until i got the timing at 35° BTDC. but is that the right way?!?

am i making this harder than is really is?!? ( wouldn't be the 1st time!!)

happy new year!!!

doug

[hardflex]

just time it normally. there are slots in under the rotor that trigger the spark, the sensor is mounted to to the base plate, so when you turn it the slots change position relative to the base plate, changing the timing.

you can't just set it at 35, because that comes in with vacuum and mechanical advance. you probably need that at 3500 rpm or so. What I would do is do that procedure at 10deg before tdc as a starting point. then check it at speed, and it should advance to approx the 35btdc mark. my 914 is set at 3500, but i don't know what yours is. ask on the 911 forum. I'm assuming a 911 if it's a 67.

PD

[mskala]

Ein 6er,
You are doing it the right way. Trial and error is the only way since no two springs are alike. I assume you don't have any vacuum advance if it is like the 911T. The initial setting before trials should be 0 degrees at 0 RPM.
Mark S.
'70 914-6

[Dave at Pelican Parts]

What Mark said.

When you twist the distributor body, you change where the pickup is relative to the shutter wheel. The shutter wheel is "fixed" relative to the camshaft position (due to the gearing of the distributor driveshaft and such). So when you twist the distributor body you change when the shutter tells the Crane to fire the spark relative to the rotation of the engine. Just like points.

The Crane instructions tell you to set the motor to TDC #1, and install the pickup so that one of the slots on the shutter is over the pickup. That gets you "close". Then you button everything up, start the engine (that's one thing "close" is good for), and run it up to 6000 RPM to check the timing with your timing light. That's what gets it "right".

Make sure to thank every power you know of that you have a Bosch distributor on that motor and not a Marelli one. A lot/most/all of the original Sixes came with distributors made by Magnetti Marelli. Almost impossible to find parts for nowadays, and nobody makes a points replacement that fits them that I have ever heard of. (Except for one or two one-offs.)

--DD

[Joe Bob]

Marelli dizzys even make lousy boat anchors.....not sure, but I think Marelli is Italian for Lucas.....

[DuckRyder]

Originally posted by mikez
Marelli dizzys even make lousy boat anchors.....not sure, but I think Marelli is Italian for Lucas.....

Actually isn't Lucas more reliable?

[Joe Bob]

They (Lucas) actually make pretty good fog and driving lights ....their electrical wiring is a bit ....ummmm, crappy?

[Jake Raby]

Lucas....The Prince the darkness...

[URY914]

I thought Lucas invented darkness.

[hardflex]

As I recall, there's about a 45degree adjustment on the sliding bracket provided (if it's like my old allison). Here's how I would set it up.

1. move engine to tdc compression
2. rotate distributor body so that the leading edge of the #1 spark plug post is directly over the trailing edge of the rotor.
3. adjust the trigger slot to line up with optical sensor using the adjustment screw on the bracket. (per Dave above)

This insures the rotor is always aligned with the spark post to keep arcing to a minimum, and will make your cap and rotor last longer.

PD

[hardflex]

oh yeah, then you have to time it by rotating the distributor to the specs.

[ein 6er]

ok ....... i got it now.

just had a brainfart, i apologize to those down wind of it!!

what a big difference rebuilding the dizzy made, it idles and revs much better. adjusting the carbs may just be a pleasure now!!

thanks again!!

doug

[nutzforporsche]

Doug,
I set mine at 35 degrees at 3500 rpm. I tried 34-36 and the 35 was dead on.
My Fireball is da chit. The only thing is that its in there tight, not much room for tweaking.

[nutzforporsche]

Oh ya I forgot something. "Happens most the time"

When I first put the unit in, I took a old dizzy cap and drilled a big enough hole in it to see the number 1 post and the shutter system. This made it a snap to adjust the phase dead on. That way you are not too far in front or behind and hit the shutter at the very edge. I was able to loosen the little screw on the diode holder and really tweak it left or right and see my progress through the hole.

Any way my .02 worth

Steve

[Dave at Pelican Parts]

Steve, remember that he's timing a six-cylinder motor. Timing specs are a little different for those than four our four-cylinder ones...

The procedure is pretty much the same, the same techniques work--but what you're shooting for is a bit different.

--DD

[nutzforporsche]

OPPs should have checked first. Ok.... icksnay on the degree timing the rest might be of some assistance. LOL

Steve