My question is where to start. I have seen where people are retarding the timing and degree of cam to what I would say are crazy numbers. But it is hard to say where to start since we are in no way dealing with exact setups or new motors, some slants are going to be more "tired" then others.
I'd start HERE:
The word on the street is, that slant 6's that are running boost should limit the total mechanical advance to 18 degrees, total.
That's to prevent detonation.
Here's an easy way to do that:
First, make sure that your timing mark on the vibration dampener is accutately positioned at when the crank's at Top Dead Center. That's in relation to the
factory pointer, or timing marker that's on the front cover plate, near the bottom.
Usuakky, they are (correctly positioned.) but not always, and it's easy to check.
The easiest way to do that is, to acquire a Top Dead Center tool (Summit probably has 'em, or Jeg's,) that will screw into the #1 sparkplug hole, just like a sparkplug does. This tool has an adjustable probe that sticks down a little way into the cylinder and will contact the piston at some point, preventing the piston from coming all the way to the top of its normal travel. The probe end of the tool should be adjusted to a length that will stop the piston about an inch from the top of its normal travel.
Turn the crank with a socket on the crank's center bolt head, slowly and
gently, until the piston hits the tool. Once it won't go any further, scribe a mark on the vibration dampener (bottom pulley,) in reference to the factory-installed timing pointer, using a sharp, pointed object, like an awl. Then reverse the rotation of the crank and turn it as far as it will go in the other direction, and scribe another mark, again, in reference to the timing pointer.
Now, split the difference in those two marks and you'll have an accurate Top Dead Center location at the pointer. If the factory did their job right, the original timing pointer SHOULD be pointing at that mark you just made.
Once you have that mark, and have ascertained that the pointer is telling you
accurately, where TDC (top-dead-center) really is, you can find the eighteeen-degree location for your
total timing mark (which will be used to set the timing) by
accurately measuring the
circumference of the vibration dampener (bottom pulley) and dividing by 20. There are 360 degrees in a circle; eighteen degrees is one-twentieth of 360. Like, DUH...
Or, put another way, measure a distance of 1/20 of the circumference of the dampener, measuring from the TDC location you just verified using that TDC tool) and make a mark with a sharpie on the vibration dampener at that point and you have your
"eighteen degrees before TDC" timing location verified.
DISCONNECT AND PLUG THE VACUUM ADVANCE LINE.
Loosen the clamp bolt that holds the distributor from rotating. Leave it just snug enough that you can, with some effort, rotate the distributor, but not "loose." You don't want it to turn on its own...
Start the engine.
Now, while the engine is running, with your timing light hooked up, you can slightly rotatethe distributor body, and watch the spark move around, forward and back, on the vibration dampener, as the engine runs...
Have someone work the throttle and run the rpm up to the point that the distributor won't advance any further. You can see, with a timing light. that at some point, the movement (advance) will "hit a wall," and stop advancing. Probably about 3.500 rpm (you need a tach to do this right.)
Now, that the engine is running at that RPM
or above, just watch the timing mark advance 'til it gets to the eighteen degree mark that you scribed into the vibration dampener clamp the distributor down using the factory bolt, and you're all set.
You MAY have to adjust the bolt that's on the bottom side of the distributor to get enough movement to accomplish this, but maybe not. That bolt is there, but you can't see it without pulling the distributor out, or using a hand-held mirror. It's pretty-well out of sight...
If I were you, I'd leave the vacuum hose disconnected for a while. You don't need that added complication at this point. Having it disconnected won't hurt anything.
The ideal situation would be to modify your distribuor so that there's only about ten degrees of advance (on the crank) built into the advance mechanism, but that may not be necessary. I'd try it "stock," first.
If it's unduly "lazy" at low rpm, you may have to do that to get suffucuent spark advance at low rpm...
I hope this gives you a place to start. Ignition timing is critical on these turbo engines, to ensure longivity (no detonation.)
Any questions, just ask; somebody here will know....
:happy1:
