Part 8 - Vacuum Advance
I was over at spector off road last week buying some misc. parts for the land cruiser, and while it was parked out back, marf started digging through it and informed me that i had a vacuum retard distributor and a non-ported carburetor.
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i stared at him for a bit and blinked.
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finally, he explained to me what all that meant, and why it was so bad (and that it was the reason my engine was running rough). as the engine turns at faster RPMs, in order for the spark to ignite the gasoline in the piston chamber and get the most efficiency at it, it has to spark a little earlier in the compression cycle (since the rate of combustion is static, but the speed of the piston, and therefore compression is dynamic). as the engine goes faster, it creates more vacuum (as it draws air into it to combine with fuel and combust). a ported carburetor is a carburetor that has a port on it that passes some of that vacuum from the engine out of the carburetor (and through a little hose) over to the distributor, so that when there is more vacuum, the distributor adjust accordingly.
well, long story short, whoever installed my carburetor and distributor put a mismatch set in there, so it was running poorly. there was a vacuum retard distributor in there but there was just a constant vacuum line hooked up to it (not ported - or variable vacuum). so it would bog down whenever i hit the gas pedal.
so i took it over to mark's off road to have mark port the carburetor (since he's mr. land cruiser carburetor man) and install a vacuum advance distributor.
he got in there and it turns out my timing was 41 degrees off. to give you an idea of how crazy that is, the distributor is a circle of points around a rotating center piece. as the engine turns, it turns that center piece and touches each one of those points (in my case, 6 of them, for 6 cylinders) in order, which forms a circuit for a brief moment and sends electricity to the spark plug attached to that point so that the cylinder fires. so if there is 360 degrees in a circle, and there are 6 cylinders, that means each point is 60 degrees away from each other. if the piston is at it's highest in the chamber (and the fuel/air mixture is compressed to it's max), and that spark plug fires at that exact moment, the timing is said to be 'top-dead-center'. the factory timing set for my engine is 7 degrees advanced, which means that little center piece should hit the point and cause a spark in the chamber, and then go another 7 degrees past the point (and towards the next point) when the piston hits the top of it's compression. well........ mark got in there, and mine was 41 degrees off. which is a little like being 9 months early for someone's birthday.

(as opposed to being 3 months late - hahhahaa). the only reason it worked, is because they also had the wires switched on the distributor, so they were going to the wrong spark plugs.
also, it turned out that my carburetor was ported after all (at the factory - not a homespun job), but for some reason they hooked up the vacuum to the unported part. no idea why. perhaps they had no clue what they were doing.
anyhow, he set the timing, rebuilt the carburetor, and dropped in a new distributor. and now she purrs. here's a shot of the cleanned up carburetor:
and, the accelerator return spring was missing the brack to attach to, so it used to be hooked to a wire hanging off the master cylinder, as shown here (i had thrown a chain on there to replace the wire, temporarily):
i picked up a bracket at spector off road, sanded it, primed it, painted it, and mark installed it when he put the carburetor back on (seen a the bottom of the photo):
and here's my vacuum advance distributor:
i also picked up one of those nice optima yellow batteries and dropped it in. now when i turn the key over, that, in conjunction with the carb rebuild causes her to fire right up (don't even need the choke):
and, mark gave me a couple of extra lugnuts to use as spacers on the battery hold-down. now i'll always have some extra lugnuts handy.
now she's almost ready for this weekend's death valley trip.
