M38A1 Timing Question

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M38A1 Timing Question

Postby M38A1 MP Jeep » Sat Apr 10, 2004 2:33 pm

Hoping someone here can help.

Here's my dilemma -

1. My electrical was coverted to 12 volts. I have a 12 volt autolite distributer, not the 24 volt military one.

2. My timing chain cover has the markings for 0 degrees (top dead center) and 5 degrees off dead center.

3. My double pulley on the bottom of the timing chain cover is not notched, marked or scribed with the mark that you would normally line up with the 5 degrees off TDC on the timing chain cover.

This is what I have done to SWAG TDC

1. Put my thumb over the #1 cylinder hole. Crank the starter. I feel a sudden draw or suction of air followed by a sudden outward push of air approximately 180 degrees opposite the inward draw of air.

I am assuming the outward push of air on the #1 is where my #1 cylinder is at or approaching TDC.

Questions

1. How do I find 5 degrees off TDC without the notch on my pulley?

2. How is the pulley usually marked? The TM shows almost a V notch towards the rear of the inner most pulley to the timing cover. I looked for that and I looked for a scribed line to no avail.

3. Can my 12 volt distributer be put in 180 degrees backwards? My CJ-5 manual shows the rotor pointing roughly to the 5 clock position when the #1 cylinder is up. I get the sudden outward push of air at the 11 o'clock position.

HELP!

Thanks

Jon
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby M38A1 MP Jeep » Sat Apr 10, 2004 3:04 pm

Thanks - I will go look for the line or the hole

Distributor is not 180 degrees off - I interpreted my rotor wrong. Helps if you slow down and really take the time to interpret the picture you are looking at
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby Wes K » Sat Apr 10, 2004 3:33 pm

The distributor can't be put in 180 Deg out unless the oil pump was indexed 180 deg out. The postion of the oil pump's shaft determines where the distributor has to go. When one sets up the engine properly the civvy distributor rotor will point towards the 5 o'clock position and the military will point towards the 7 o'clock position. The correct way to index the oil pump shaft is to get #1 piston TDC on compression. Then align the cam and crank gear's timing marks. Then install the pump so the shaft's slot is in the correct position in the manual.

Folks in the field do not want to pull the crank pulley and timing cover to do it right. So they have 3 or 4 Half arse ways to APPROXIMATE TDC of #1 piston on compression and then mark the crank pulley to match the TDC mark on the tab. The closest of these ways to get #1 TDC is to use a dial indicator thru the plug hole or pull the head and put the dial indicator on the top of the piston. Even with this method you are lucky to be withing 4 or 5 degrees of the true TDC since there's 3 or 4 degrees of crank rotation at TDC that doesn't produce any discernable vertical movement of the piston.

Since ignition timing can have such a great impact on drivability, fuel burn and cumbustion chamber temps anyone not very comfortable with the mechanical work should seek the help of an experienced mechanic to be there when you're doing this. It saves a ton of money in the long run and you'll get to learn how to do it correctly first hand the first time around.
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Postby M38A1 MP Jeep » Sat Apr 10, 2004 6:10 pm

I found the whole on the curved part of the innermost pulley, almost flush against the timing chain cover.

So I should be able to line that whole up with my 5 degrees off top dead center and be ready to go to the next step to start my engine...

Am I headed in the right direction?

By the way, my distributor was not 180 degrees off as I thought it was - I thought the tab that arches up from the rotor and points over the rear of the rotor was the fron of the rotor. I relooked my CJ-5 manual with the civilian distributor and realized I misinterpreted the picture. I am going to assume my oil pump is indexed properly...
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby M38A1 MP Jeep » Sun Apr 11, 2004 7:11 pm

I lined up the hole on the rear of the innermost pulley with the 5 degree off TDC mark on my timing chain cover.

Wes mentioned the distributor should point to the 5 o'clock position on the civy distributor (WHICH I HAVE) and 7 o clock on the military one.

It points to the 8 o clock position. Any idea what this means?

On another note - I know when you have the engine indexed to 5 off TDC and you start the engine, you can use a timing light and or tune the engine by ear by turning the distributor while it is running.

My distributor was not scribed in relation to the rotor when removed. How should I initially place my distributor in relation to its arc of movement? All the way right, left or center of its movement?
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby Wes K » Sun Apr 11, 2004 9:24 pm

[quote="M38A1 MP Jeep"]I lined up the hole on the rear of the innermost pulley with the 5 degree off TDC mark on my timing chain cover.

Now open the distributor cover and check point gap at .020. Bring the rotor to the #1 plug firing position. Loosen the distributor adjusting bolt. Rotate the distributor slowly clockwise till the points are closed. Now very slowly rotate the distributor counter clockwise until the points jsut begin to open. Tighten the adjusting bolt.

Now mark the notch or hole in the pully and the 5 deg mark with a yellow crayon or anything to make them easier to see. Since you have a civvy distributor and conventional plug wires just connect your timing light to # 1 plug wire and fire her up. If she needs adjusting just loosen the bolt and roatte accordingly and when hitting on 5 deg mark tighten bolt.

Wes mentioned the distributor should point to the 5 o'clock position on the civy distributor (WHICH I HAVE) and 7 o clock on the military one.

It points to the 8 o clock position. Any idea what this means?

Just means the oil pump wasn't set up exactly right.

On another note - I know when you have the engine indexed to 5 off TDC and you start the engine, you can use a timing light and or tune the engine by ear by turning the distributor while it is running.

Only old timers with bad hearing are good at tuning by ear. You don't tune anything but your voice by ear. Since + or - 1 degree is our goal when timing why would you use your + or - 20 degree ear timing?

My distributor was not scribed in relation to the rotor when removed. How should I initially place my distributor in relation to its arc of movement? All the way right, left or center of its movement?

You don't get any choice. You bring #1 up on it's compression stroke. You line up the hole in the crank pulley with the 5 deg mark. Look in the dsitributor mounting hole and see the position of the oil pump drive shaft's slot. The distributor will fit in that slot only ONE way.
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Postby M38A1 MP Jeep » Mon Apr 12, 2004 5:00 am

Thanks.

Does my oil pump not being set up right, as my distro is pointing to the 8 o clock position indicates a major problem?

You said

"Now open the distributor cover and check point gap at .020. Bring the rotor to the #1 plug firing position. Loosen the distributor adjusting bolt. "

Should I be able to turn the rotor cap easily by hand back to the 5 o'clock position?

Last question - I don't have a timing light and need to get one. Are they all the same or is there anything special I should look for?

Thanks for the information - just enough to be dangerous :)

Jon
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby Wes K » Mon Apr 12, 2004 7:58 am

The main reason for getting the oil pump set up correctly is to make sure you'll have adequate room to rotate the distributor thru it's full range of timing adjustment (About 70 or 80 degrees of rotational travel.). This is not usually a problem with civvy distributors that have no external appendages and are round. But the military distributor is not round and some civvy distributors have a vac advance sticking out.

Since you have never timed an engine before and you are not familiar with the relationship of crank and cam travel in degrees vs point gap (dwell) and opening position you really should have a mechanic go thru it with you first.

The inductive pickup lights are the easiest since you have conventional wires.
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Postby M38A1 MP Jeep » Mon Apr 12, 2004 8:03 am

Wes

I hear you 100% on having the mechanic help me out. My dilemma is I have a non-running vehicle, am new to the area, and don't really want to have it towed somewhere unless I really have to.

Perhaps thats's what I'll need to do.

What's the worse case situation once I get my fuel lines run if I go to fire her up and she is off?
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
M38A1 MP Jeep
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Posts: 1796
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Timing Dilemma Update

Postby M38A1 MP Jeep » Thu May 13, 2004 7:56 pm

I have lined up the hole in the backside of the fan belt pulley with the 5 degree off TDC mark on the timing gear cover, and this is the rotor placement looks right now:

Image

As you can see, it appears that even though the hole is lined up correctlu with the marks, the rotor points to the #3 firing position instead of the #1 firing position within the distributor. I used the following as a reference:

Image


I think Wes indicated that my oil pump may be indexed incorrectly. Does this appear to be the case?

Should I reindex my oil pump, and if so, how difficult is that to do?

I have the CJ-5 civilian distributor. It was working when pulled out of my seized engine and is now being placed into a completely different motor. Nothing was scribed as many of the manuals recommend doing when a distributor is pulled. I found the following suggestions for what is called "Initial spark timing" and "static timing".

Initial spark timin is described as follows:

" Rotate the crankshaft slowly, and stop exactly where the timing marker indexes with the 5 degree advance mark. Turn the ignition switch to the ON position. With the distributor clamped loosely, move the housing in the direction of the shaft rotation (counterclockwise), well past the #1 cylinder disributor lobe. Now, very slowly rotate the housing clockwise toward the #1 cylinder firing position. Watch the point contacts carefully. At th exact moment the points arc, you will have set the timing to 5-degres advance. For start up purposes, this is a highly accurate method "

Static timing is described as follows:

" With the spark plugs removed from the engine, rotate the crankshaft to locate the timing marks as before. Now, reinstall the distributor cap. Place an old spark plug on #1 plug wire and ground the plug's metal shell. Loosen the distributor housing clamp. Turn the ignition switch to ON. Rotate the distributor housing counterclockwise a few degrees, then slowly rotate the housing clockwise until a sparkfires across the test plug. If you tighten the distributor at this exact point, accurate timing results"

Is one of these methods best?

If so, does "turning the ignition switch ON" mean that the starter is moving the engine through it's full range of motion until the spark happens? I ask because I am using my push button on the solenoid as I don't have an ignition switch set up yet. I have an OFF/ON switch on the dash board and a floor switch that would normally activate the starting process.

How do I get the current to run across the distributor to the #1 spark plug (staic timing) or to rotate to where the points arc (initial timing) when my solenoid switch jumps the distributor across a significant arc at any given push? Can I run a jumper or something across a couple of leads to simulate the ignition switch.

Thanks for your insight and help.

Jon[/u][/b][/i]
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby Wes K » Thu May 13, 2004 9:24 pm

Jon,
The best advice you'll recieve at this point is to get an experienced mechanic to show you how to do it once and you'll not have any further problems. This may not be possible for some reason in your case and your location. But it would be worth the proverbial "Picture is worth a thousand words"! I can come over to your garage and with only 8 or 9 sentences walk you thru this entire process. As you will soon see it takes volumes of typing to accomplish the same thing from here.

Correct indexing of the distributor is to ensure you have enough swinging room to rotate the distributor when timing adjustments are needed. It is more critical when the distributor is large or odd shaped or has a large vacuum advance unit sticking out that dictates starting with a basic porition of installation of the distributor. With the simple round distributor you have and no objects purtruding from it you can leave it where it is as long as you can adjust it's rotational location so the spark occurs at 5 degrees BTDC. Wherever it points just put #1 wire in that hole and install the other three in their correct sequence and direction.

Both of your timing examples do the same thing. You do NOT use the starter to rotate the engine or distributor. The first program uses a spark across the points as your indicator of where to lock the distributor down and the second program uses the spark at the plug for the same purpose.

I have a few questions for you.
1-You say the timing hole is in the fan pulley and not the crank pulley?

2-You say you are moving the distributor to a different engine? Is this going to be the engine that will stay in your M38A1?

3-Have you confirmed that this new engine has #1 piston at TDC on compression with both intake and exhaust valves closed,
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Postby M38A1 MP Jeep » Fri May 14, 2004 4:48 am

Wes -

The timing hole is on the crank pulley and not the fan pulley. Oversight on my part here.

Yes, the distributor was moved from one engine to another and it will be the engine the distributor stays in.

I have not confirmed that this new engine has #1 piston at TDC on compression with both intake and exhaust valves closed unless you count lining up the timing hole on the crank shaft pulley with the timing gear cover index markings. What is the trick to doing this?
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby Wes K » Fri May 14, 2004 8:29 am

This is why I recommend having a mechanic walk you thru this in person. I am not an eloquent enough writer to describe the fell and touch involved.

The short version is those marks will line up twice for #1. I'll skip the long explanation about how 4 stroke engines work. You need a helper. Pull all four plugs out. Hold your thumb in the #1 plug hole while your assistant rotates the crank manually untill you feel the greatest amount of air pressure against your thumb. When that happens lighten the pressure up on your thunb so the air can escape with an audable hiss. When the hiss stops the piston is at TDC and have your assistant stop turning the crank immediately. Now you should only have to rotate the crank backwards a very little bit to align the timing marks. Now insert the distributor. WEhen it is firmly seated in place install the bolt loosely that retains it. Now rotate the distributor counterclockwise (CCW) as viewed from the top looking down until the points are closed. Now place a piece of plain white paper between the point contacts. Maintain a slight pull on the piece of paper while you very slowly rotate the distributor clockwise (CW) as viewed from the top looking down. Stop the instant the paper starts to slip out of the points. Lock the distributor here. Now place #1 plug wire in the tower the rotor is pointing at. Add the remaining three wires in order. Voila, install the cap, plugs and connect the wires to the plugs and start her up.

Engine can be turned over manually by using a socket and ratchet on the crank nut or by placing your left hand on top of the two fan belts about halfway between the generator pulley and the waterpump pulley and apply a little downward pressure then with your right hand turn the fan clockwise (CW) as viewed from the the front of the engine lookming towards the engine.
Last edited by Wes K on Fri May 14, 2004 9:07 pm, edited 2 times in total.
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Postby M38A1 MP Jeep » Fri May 14, 2004 8:43 am

Wes -

Perfectly described. Thank you, I will give it a shot this weekend.

One last question - What's the easiest way to turn the crank over as you described with all the pulleys connected together via the felt belt and with all the plugs in except for the #1. It does not turn by hand easily like it did without the fan belt and plugs installed. Large wrench? Socket?

Jon
I am seeking information on M38A1's configured for MP use from 1953-?.

I am also interested in equipment and uniforms worn and carried by MP's during this timeframe.
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Postby Wes K » Fri May 14, 2004 9:31 am

As I said in the last post. Pull all four plugs. I forgot to give you options for turning the engine by hand. One is a socket on the crank pulley nut and two is place your left hand on top of the two fan belts between the generator pulley and the water pump pulley and apply some down pressure. Then with your right hand rotate the fan clockwise as viewed from the front looking at the engine for normal cranking rotation.
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