Timing crank trigger ignitions...

[69rsss350]

I know there are some very knowledgeable gearheads on this site...
I am looking for a tutorial on timing my crank trigger ignition. (72 Vega Wagon 454cid S/G car).
Thanks, Mike

[Yellow 69 z28]

Mike,

Crank triggers set ignition timing off the rotation of the crank. Your BBC chevy should have a crank wheel bolted to the front of your harmonic balancer. This wheel should have 4 permanent magnets mounted at 90* apart. Also bolted to the front of your block should be a bracket with a pickup sensor mounted to it. As the crank rotates the magnetic field from the magnets trigger the sensor to turn on the coil via a ignition box.

With all this said your distributor is now only pointing the spark to the cylinder and all timing advance mechanisms' should be locked out or removed. I will go into phasing the distributor later. All timing controls must be locked out of the distributor because ignition timing is now set at the crank.

So if your race engine needs to have a ignition curve you need to do it as an accessory to your ignition box not in the distributor. (I run total advance all the time and use a timing control that retards the ignition at start-up until it lights off. I can also set the total amount of advance with a specified range, 34* to 40*, as conditions change.)

Assuming that your engine fires up and runs, you will need to hookup a timing light, preferably an adjustable light, disable all timing controls (make sure this means the distributor) and read the timing. When you use a adj. timing light you should keep advancing the knob until the balancer mark matches up to the pointer, basically on TDC. Now reading the timing light's knob setting is what your engine ignition timing is set at. (Timing Light 101.) Timing should be between 34* and 38* total advance. Also assuming your balancer is marked for TDC and your pointer is set for TDC also.

This is critical for an accurate reading, so if you do not have a pointer that sets TDC you must find this before you can start tuning.

Once you know what your timing is set at you can start phasing. Setting your timing is done with the crank sensor, you should be able to move it in its bracket up and down while maintianing a .035 to .050 end clearance between the sensor and the wheel. Depending on which side of the block the sensor is mounted, drivers or pass., will determine which way, up or down, the sensor needs to move to advance or retard. And going back to the top dead center concern the sensor should of been initially set so you have enough movement left in the bracket to go adv. or retard.

Now for phasing of the distributor. Once you timing is set to where you want it you will need to phase the distributor cap. Take an old cap and drill a big enough hole in the top in line with number one plug wire so you can see the rotor contact point to #1. I usually drill the hole about 1/4 inch or more away from the #1 post. Then mark the rotor contact with a bright marker only in the section that will show through the cap. With this all done put the distributor together wire up the cap and loosen the tie down so you can just turn the distributor with you hand. Hookup the timing light again and set the knob to 0* (no advance), stark the engine and point the timing light at the hole in the top of the cap so your can see the rotor's bright marker mark. This should pointing to the dead center of #1 plug wires binding post. If it is not pointing to #1 then you will need to rotate the distributor until it is in-line. Be careful not to get your hand near that hole because 40,000 volts hurts. Once you are phased you can lock down the distributor and swap a good cap back on.

Now this should get you in the right direction to start tuning your timing for track conditions.

Hope this helps. Good luck!

[69rsss350]

Super. Thanks! You are a /ubbthreads/images/graemlins/scholar.gif

[Chevy454]

Excellent post! I love reading stuff like that!

Sounds like you're ready to go racing now, 350!

[69rsss350]

Raced last night, have yet to get this thing tuned properly but needed some seat time as I now only have 14 passes under my belt in this car. I race in Albuquerque where track elevation is 5100 feet. Went 5 rounds and won a little money. Best pass was 10.74 (converts to 10.06), best mph 126.822 (135+), best 60 foot 1.543 (horrible), best reaction .026 (gotta learn to slide the thumb off the button instead of lifting). Have yet to launch it up against the limiter which only has a 4800 chip for now (5500 stall converter). I get one more T&T before the big Memorial Day race next weekend. It's a kick though! /ubbthreads/images/graemlins/burnout.gif