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How to set #1 atTDC


fordmerc

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I want to set piston #1 at TDC. I cannot drop a dowel into the spark plug hole since the piston is off to the side. I cannot see the valves well enough to determine closure. The method of placing a finger on the spark plug hole and feeling for pressure seems imprecise, as does putting a plug into the hole and watching it pop. Would using a pressure gauge to check for max pressure work? Any other methods?

How can I easily turn the engine slowly to that point? Using the starter causes abrupt movement of varying distances.I cannot access the nut on the vibration damper. Trying to turn the  fan just can't turn the engine. I can move the engine with air pressure applied to  one other cylinder, but the movement is similar to using the starter. I've been told to expose and turn the flywheel, but that is a project unto itself. I tried to turn one rear wheel while the transmission was in gear, but the wheel and driveshaft turned but not the engine!?!? I also tried  turning one wheel with both  rear wheels off the ground- which , as expected, did not work  and I also tried to turn the driveshaft itself - which turns, but the engine did not. I can't understand that. (All of the spark plugs were removed during the above maneuvers.)

Comments and advice will be appreciated. Thanks.

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With the spark plugs removed, place transmission in high gear, release parking brake. Now you can move the car forward or backward to get the engine to TDC.

 

Surprised that with the spark plugs removed you are not able to turn the engine with the fan.

 

You could also place a compression gauge in #1 cylinder and watch it build pressure as it approaches TDC. Then watching timing marks line up for TDC.

 

Also, also, note the position of the rotor to the #1 cylinder wire on the distributor cap. You can turn the engine and watch the rotor as it approaches the location, then match up your timing marks for TDC.

 

Either way, easirer than trying to bump the engine with the starter.

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The car is my '41 Packard 120. My timing is off and alining the timing marks with the pointer when the rotor points to #1 does not solve the problem, thus I want to ascertain that the piston TDC is the same as the marks for TDC. A timing chain jump seems an unreasonable explanation, but I am desperate. I will try rolling the car forward in 3rd gear to move the engine; that should have been obvious to me.

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When I want to turn the engine over slowly and precisely, I use a spanner tool. You will need to remove the lower clutch inspection cover.  It is easiest if you have a helper to watch for the timing mark.

 

 

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If the driveshaft turns but the engine doesn't, your car must have overdrive which is not locked out.  Pushing the car with the overdrive engaged will not turn the engine.  To find TDC, take the valve chamber cover off and turn the engine until #1 intake valve just closes and the exhaust valve is also closed.  The TDC mark should be at or very close to the pointer.

 

Terry 

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Not sure if it'll work on on the Packard but one method of checking TDC on side valve engines is to feed a length of cord down the No.1  spark plug hole, turn the engine over by hand until it compresses the cord against the head and stops the motor.  

 

Mark that position on the front pulley then turn the engine back the other way until the cord stops the engine rotation again and mark the pulley at that point.

Measure the distance between the 2 marks and halfway is TDC.  

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  • 3 weeks later...

Surely you can bend a wire to feel for piston movement, or in your case lack of.

.

Good idea, but perhaps a slightly safer thing to use would be a length of solder wire.
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I had to do this recently on a 1966 Dodge slant six. The points were corroded from sitting so I pulled the distributor and replaced the points on the work bench, as being the most convenient way.

 

Then I had to retime the engine from scratch. I used the balloon on a pipe trick. The pipe was a piece of pipe about 6" long  welded to an old spark plug, I made years ago.

 

Removed the spark plugs, screwed the pipe into #1 cylinder. Stuck a balloon on top, held by a tie wrap.

 

Used a jumper cable to the starter, turned the engine in short bursts until the compression on #1 blew the balloon up. The timing marks were within 3 or 4 inches. Turned the engine by pulling the fan until the timing marks lined up , easy with the plugs out.

 

Made sure the rotor was pointing to #1 plug wire (had to take out the distributor and move the rotor a bit).

 

Set the timing using a 12 volt test light (turn the distributor slowly forward, when the light goes out lock down the distributor)

 

Put the plugs and plug wires back in place. Got in, turned the key, and it fired up instantly.

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I am not familiar with Packard engines but I wonder if there is a pipe plug on the cylinder head leading into the combustion chamber like the Chrysler family flathead engines. On them, it is at # 6 cylinder and is directly above the piston. Remove the plug and insert a straight rod like a welding rod etc. Rotate the engine clockwise very slowly until the rod stops rising and mark the front pulley with a mark lined up with the pointer. Now, rotate a few degrees past and then begin to rotate counterclockwise. This time, as soon as the rod stops mark the pully again. Exact TDC is between the two marks.

 

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I had to do this recently on a 1966 Dodge slant six. The points were corroded from sitting so I pulled the distributor and replaced the points on the work bench, as being the most convenient way.

 

Then I had to retime the engine from scratch. I used the balloon on a pipe trick. The pipe was a piece of pipe about 6" long  welded to an old spark plug, I made years ago.

 

Removed the spark plugs, screwed the pipe into #1 cylinder. Stuck a balloon on top, held by a tie wrap.

 

Used a jumper cable to the starter, turned the engine in short bursts until the compression on #1 blew the balloon up. The timing marks were within 3 or 4 inches. Turned the engine by pulling the fan until the timing marks lined up , easy with the plugs out.

 

Made sure the rotor was pointing to #1 plug wire (had to take out the distributor and move the rotor a bit).

 

Set the timing using a 12 volt test light (turn the distributor slowly forward, when the light goes out lock down the distributor)

 

Put the plugs and plug wires back in place. Got in, turned the key, and it fired up instantly.

 

Rusty,

Good explanation.

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The balloon idea is interesting .  Does the balloon just partially inflate on the exhaust stroke, or not at all ?

The balloon inflates only on the compression stroke, deflates if you go past top dead center. How much it inflates depends on the displacement of the engine. It provides a visual signal of when the compression stroke is occurring. When the balloon inflates, you are on the compression stroke. I stop turning the engine with the starter and turn it the last bit by hand, until the timing marks line up. With the spark plugs out the engine turns easily.

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