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Difficulty setting timing on 20r

Old 10-02-2016, 07:58 PM
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Difficulty setting timing on 20r

Truck: 1980 hilux 4x4 20r, 4spd.

Background:
Tore apart to do headgasket, had head gone over, surfaced, etc. New timing chain, radiator, thermostat, header, water pump, oil pump, radiator, cap, rotor, wires, ignition coil and module. Ignition coil/module are GM, did the swap.
Posted last week having difficulty trying to get the engine running; adjusted valve lash again and the engine runs.

The problem is now that the timing is extremely off. When I set the engine at TDC on compression and adjust the distributor until the rotor is sparking #1 plug, the engine runs but barely. When any throttle is applied, it either immediately dies or it begins backfiring (loudly) out of the carb and slowing down. When the engine is cut off, it will occasionally backfire as it slows to a stop.

With a timing light, the timing appears to be set about 15 degrees before after TDC. In case I'm wrong, when shining the timing light at the harmonic balancer with it running, the mark is 15 degrees or so clockwise of the 0 BTDC mark on the oil pump (too far to the right). edit-This is with vacuum advance lines pulled and plugged. With them attached, the engine runs better and the timing is at 3 degrees or so after TDC. I'm attempting to get the timing set at 0 BTDC with the lines disconnected.

My first thought was that the distributor was "off a tooth". Reinstalling the distributor with it moved one tooth in either direction causes a no-start. While the engine is running, turning the distributor clockwise causes it to slow down and die, turning it counter-clockwise increases idle speed until rotation is stopped by the retaining bolt (which I discovered seals a hole in the cylinder head by the way. For other newbies, running the engine without that bolt in will spray oil everywhere). Counter-clockwise rotation retards(?) the timing, moving the mark counter-clockwise towards 0 but no where near enough.

I examined the distributor, and checked that the springs are not binding in the advance mechanism.

Thoughts stewing in my ignorant brainmush:

When I installed the timing chain, perhaps I misaligned the bright links, leaving the timing between the crankshaft and cam slightly off.

My ignition setup is janky cause I'm a numbnuts.


Clueless here, any help would be awesome. What steps should I follow to isolate the problem and figure out what I did wrong?

Last edited by meowmix123; 10-03-2016 at 11:17 AM.
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Old 10-03-2016, 09:43 AM
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When installing the distributor, the rotor should be just counterclockwise of the number one spark plug lead with the crankshaft and cam set at TDC. Timing should be set at eight drgrees.
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Old 10-03-2016, 09:56 AM
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I meant after TDC on the harmonic balancer, the timing mark is 15 degrees or so past 0.

I'm going to take a look at the truck tomorrow and see if frustration caused a stupid error, wouldn't be the first time.
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Old 10-03-2016, 11:13 AM
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Originally Posted by mwisham View Post
When installing the distributor, the rotor should be just counterclockwise of the number one spark plug lead with the crankshaft and cam set at TDC. Timing should be set at eight drgrees.
To clarify, this is precisely what I am attempting to do; when I do this, the timing with the vacuum leads pulled and plugged is 15 degrees after TDC, with the lines attached it is about 3 degrees after TDC. With the lines attached it runs better, but still obviously very rough as it's firing on the beginning of the down stroke. This is what is driving me nuts- changing the tooth the distributor is on in either direction, which should advance or retard the timing from my understanding, causes the engine not to start. I've replaced a distributor before on a 22r with no issues, but I was just doing that one part.
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