Correct distributor insertion for 250 L6?

[jcwren]

OK, I'm confused (nothing new here!). The distributor wasn't installed when I bought the truck. Reading the service manual, it says set the engine to TDC on the compression stroke. I'm using the timing mark on the pulley and the timing mark plate to set TDC, which jibes with the position of the piston. No problem. Then the following:

2. Position distributor to opening in block in normal installed attitude (fig. 19i and 21i), noting position of vacuum control unit.

3. Position rotor to point toward front of engine (with distributor housing held in installed attitude), then turn rotor counter-clockwise approximately 1/8 turn more toward left cylinder bank and push distributor down to engine camshaft. It may be necessary to rotate rotor slightly until camshaft engagement is felt.

4. <blah blah to get distributor to fully seat>

5. Turn distributor body slightly until points just open and tighten distributor clamp bolt.

6. Place distributor cap in position and check to see that rotor lines up with terminal for No. 1 spark plug.

Picture 19i (page 6Y-31) is worthless. It's a side view, total lack of perspective. This appears to result in the rotor pointing at cylinder #1. First, step 5 doesn't indicate WHICH way to turn the distributor body. Rotating it counter-clockwise has the vacuum advance port pointing just about into the block, while turning it clockwise has it pointing almost directly at the battery tray. And in neither case is the rotor pointing to the number 1 cylinder on the distributor cap, which is where I would think it should be when you're setting it at 0 degrees TDC.

So what's the correct way for installing the distributor shaft and statically setting the distributor body for first start?

This is a picture of my distributor as installed per step 3. Attached is someone else's L6 that I'm using as a reference.

[RichardJ]

>> TDC on the compression stroke. I'm using the timing mark on the pulley and the timing mark <<

This is a 4-cycle engine that turns two complete revolutions of the crankshaft or 720 degrees of rotation for each cylinder firing event. For each firing event the TDC mark lines up twice, but fires every other revolution.
The plug must fire at TDC Compression Stroke, but not on the TDC Exhaust Stroke.

If you don't understand that or can't determine TDC Compression, then stop.

On your #3 ............. 1/8 turn more toward left cylinder bank and ...............
An inline engine doesn't have a left bank, so I'm not sure what you are reading.

I've seen that picture with the green circles before. The guy that originally posted that picture did not understand what he was doing. He seemed to think the rotor needed to be pointed to the spark plug in the #1 cylinder.
You correctly understand that the rotor points to the #1 wire tower on the cap.

#4 is all about getting the distributor to drop down onto the oil pump slot and still keeping the rotor pointed the way you want it to. On a six, it is very easy to reach down to the pump with a screw driver and light.

Static timing with points distributor.
1. Move the crank timing mark to about 6 degrees BTDC. ( On the compression stroke)
2. Rotor pointing to #1 plug wire on cap.
3. Remove #1 plug wire from #1 spark plug and attach any old spark plug to it. Place the plug on any unpainted surface on the engine so the plug body is grounded.
4. Turn ignition key to "ON".
5. Rotate distributor body back-and-forth until you see the old plug fire. Do this as many times as needed to feel comfortable that you have found the correct spot when the plug fires.
6, Reconnect the plug wire to the #1 plug and start engine. If you were careful, your timing light will show that you are within 2 degrees.

[jcwren]

Originally Posted by RichardJ

>> TDC on the compression stroke. I'm using the timing mark on the pulley and the timing mark <<

This is a 4-cycle engine that turns two complete revolutions of the crankshaft or 720 degrees of rotation for each cylinder firing event. For each firing event the TDC mark lines up twice, but fires every other revolution.
The plug must fire at TDC Compression Stroke, but not on the TDC Exhaust Stroke.

If you don't understand that or can't determine TDC Compression, then stop.

This much I do know

On your #3 ............. 1/8 turn more toward left cylinder bank and ...............
An inline engine doesn't have a left bank, so I'm not sure what you are reading.

Reading straight from the service manual, "ST_133-70 Chevrolet Truck Chassis Service Manual Serial 10-60", page 6Y-31, "Installation -- Engine Disturbed (All Models)", step #3. It covers both the V8 and L6, sometimes in the same paragraph. For the L6, I took this to mean the ONLY cylinder bank.

I've seen that picture with the green circles before. The guy that originally posted that picture did not understand what he was doing. He seemed to think the rotor needed to be pointed to the spark plug in the #1 cylinder.
You correctly understand that the rotor points to the #1 wire tower on the cap.

#4 is all about getting the distributor to drop down onto the oil pump slot and still keeping the rotor pointed the way you want it to. On a six, it is very easy to reach down to the pump with a screw driver and light.

Agreed. Their suggestion is to bump the engine, I've just been turning the engine by hand (plugs are loose) until it drops down. The distributor gear is engaged even though the oil pump is not.

Static timing with points distributor.
1. Move the crank timing mark to about 6 degrees BTDC. ( On the compression stroke)
2. Rotor pointing to #1 plug wire on cap.
3. Remove #1 plug wire from #1 spark plug and attach any old spark plug to it. Place the plug on any unpainted surface on the engine so the plug body is grounded.
4. Turn ignition key to "ON".
5. Rotate distributor body back-and-forth until you see the old plug fire. Do this as many times as needed to feel comfortable that you have found the correct spot when the plug fires.
6, Reconnect the plug wire to the #1 plug and start engine. If you were careful, your timing light will show that you are within 2 degrees.

The plug should fire just as the points open. I've seen the suggestion of using a ohmmeter to determine when the points open. Any reason to avoid that method?

Good stuff, thanks!

[RichardJ]

If you have everything covered, then what is the issue?

>>until it drops down. The distributor gear is engaged even though the oil pump is not.<<

If it drops down, then it should be in the pump ????

>>plug should fire just as the points open. I've seen the suggestion of using a ohmmeter to determine when the points open.<<

All true. You can even use a 12 volt test light.

That will show the dist points are working. It won't show if the rotor is lined up with the #1 plug wire or not. It won't show if you have mistakenly set the engine on #6 Compression Stroke, better known as #1 Exhaust Stroke.

The goal is to fire the #1 spark plug and fire it at the correct time. If a plug on the end of the #1 plug wire fires statically, it shows you have set everything up correctly from the plug BACK.