L18 timing jumping all over?

[sanyantho]

Hi Ratsuns,

      I have a 74 620, after setting my timing, and locking the distributor. My truck timing keeps jumping from 12% BTDC to 5% then back up to 15%. It wont stay at 12% BTDC. When I press on the distributor cap it seems to rev high, when I let go, it revs low.  I changed the plugs and wire, but not the cap and rotor. What can be the problem? Thanks

[bilzbobaggins]

Where's your idle set at? What kinda carb?

[sanyantho]

12% BTDC, weber 32/36 thanks

[datzenmike]

Hi Ratsuns,

      I have a 74 620, after setting my timing, and locking the distributor. My truck timing keeps jumping from 12% BTDC to 5% then back up to 15%. It wont stay at 12% BTDC. When I press on the distributor cap it seems to rev high, when I let go, it revs low.  I changed the plugs and wire, but not the cap and rotor. What can be the problem? Thanks

 

 

This is not normal. Replace the cap and rotor and report back.

 

 

also...

Your idle has to be around 750 800RPMs when setting the timing. If it won't go that low or wanders try adjusting the idle mixture screw...

 

1/ Turn the idle speed as low as possible.

2/ Turn the idle mixture screw in or out to find the fastest smooth idle speed. There will probably be a full turn where nothing much happens, set roughly in the middle.

3/ The idle has probably gone up so turn it back down and repeat 1/ and 2/ to get the fastest smooth idle.

4/ turn the idle speed back down and keep repeating 1/ 2/ and 3/ untill you cannot improve the idle quality and the speed is around 700-850.

 

Once idle is solid now check or set the timing. It will likely be ok now.

[sanyantho]

Hi Mike,

    I knew you would come thru for me. How do I know if my truck is idling at 700-800 rpm without a tachometer? I will buy a new cap and rotor, try my best to adjust the idle and report back. Thank you!

[DanielC]

With older cars, A low speed tachometer is a necessary piece of equipment.  Go to an auto parts store, and ask for a dwell Tachometer, or on line search for one.

[sanyantho]

Thanks Daniel, will do!

[DanielC]

A vacuum gauge will help you set the idle mixture also.

[banzai510(hainz)]

is the bushing loose on the distributor?

 

wiggle the shaft side to side. Maybe its getting worn out.

[sanyantho]

Here is an update everyone...

 

1. Bought new cap, rotor, and points from an auto store. Bought a dwell tachometer from Harbor Freight.

2. Installed new cap, rotor, and points. Gap points with feeler gauge at .50 mm. Used the dwell tachometer to test the rpm, display shows that rpm jumps around from 500-800 rpm. But the engine is idle steady.(Not sure if the dwell tachometer is working correctly) Used the same tach to measure dwell angle and it display 80.( Again not sure if that is correct)

3. After all this, I tried to set the timing. Close I can get is 25 BTDC, by turning the dizzy counter clockwise until it can not go no further.

 

Other than that, my truck seems to be running great. I was able to drive around town with no problem. Should I just drive her until the wheels fall off?

 

Hainz,

    I will try wiggle the shaft tomorrow. Thanks

[datzenmike]

500-800 RPM is not much to hear the difference of and this is why the tach is useful.
 
 
 

Hi Ratsuns,
      I have a 74 620, after setting my timing, and locking the distributor. My truck timing keeps jumping from 12% BTDC to 5% then back up to 15%. It wont stay at 12% BTDC. When I press on the distributor cap it seems to rev high, when I let go, it revs low.  I changed the plugs and wire, but not the cap and rotor. What can be the problem? Thanks

 

You can't have the above and now have 25 BTDC.

 

1/ take the vacuum advance hose off when checking and see. Any change?

 

2/ Suck on the vacuum advance hose to the distributor while looking at the rotor. What you should see is the rotor turn clockwise and return when released. Does it?

 

3/ Set to TDC compression stroke #1 cylinder. Use the timing notch on the pulley and the timing scale by the alternator. Must be TDC!

 

http://community.ratsun.net/topic/64664-how-to-find-tdc-on-the-1st-cylinder-on-l16-engine/

 

 

Now remove the two bolts holding the distributor to the timing cover and lift out. (don't worry, this will not change the timing you have set) This is what you should see...

 

 

Note there is a small and large half moon. Does yours look like the above???

[sanyantho]

Hi Mike,

 

1/ take the vacuum advance hose off when checking and see. Any change? < Which end? from the carb or the distributor?

 

And when I find the TDC, how do I line up the main pulley to zero? Do I unloosen the big nut on the pulley and move it to point to zero?

[datsunaholic]

1/ take the vacuum advance hose off when checking and see. Any change? < Which end? from the carb or the distributor?

 

Doesn't matter which end of the hose, though pulling it at the dist makes it easier to plug the line when idle set testing.

 

And when I find the TDC, how do I line up the main pulley to zero? Do I unloosen the big nut on the pulley and move it to point to zero?

 

You just turn the engine (with a wrench!) until the timing mark aligns.  Easier with the plugs out (compression can make it want to back up).   You're turning the whole engine, not just the pulley.

 

 

 

If the distributor shaft is wobbly it'll make the timing jump around (and make the idle speed appear erratic)

[datzenmike]

-how-to-find-tdc-on-the-1st-cylinder-on-l16-engine/

 

This works on an L18 also

[sanyantho]

Thanks Mike and Aholic, I will try it out and report back! :thumbup:

[banzai510(hainz)]

open the oil cap. pull the center spark plug wire to the distributor.

 

now look in the oil hole and that lobe is your intake lobe, hit starter qickley till the lobe is pointing to the left. when it is shut the key off. then crab with your hands the pulleu and turn right(clock wise till the Zero mark in the pulley is lined up to zero.  THIS is TDC.  you can open your dist cap and see how far away the rotor is to the number 1 plug wire.

 

 

Im confused as you got it to 12deg BTDC BEFORE!!!!!!!!  so why is it now 25BTDC

 

 

 

I just adjust a guys 620 and he was so far RETARDED on his dist that I don't know how he was running it like this . I adjusted the 8mm bolt under the dist to loosen the timming plate. tghen recentered by using the timming light crancking the dist to one side it needed to go. put the timming plte in the middle then tighten the 8mmbolt  then fine tune the adjustment to 1odeg BTDC and then adjusted the mixture and the speed screw as he had this cranked to many turns as it was above idle speed..

[sanyantho]

Hi Ratsuns,

     Reporting back.

1. Found the TDC by plugging my finger into the #1 spark pug, also checked that first 2 lobe was at 10 and 2 clock position. Timing mark was pointing to 0 degree.

2. Pulled the dizzy and the shaft was leaning a little toward the 12:30 clock position not 11:25 as it should. Dizzy wiggles a little, if I dont have the screws tight. With the 2 screws tight, it doesnt wiggle. Also sucked on the hose to the dizzy and the rotor moved clockwise and back as it should. But I had to suck on the hose really hard.

3. Removing the advance vacuum hose and checking rpm, didnt change.

4. Check the timing and it was still at 25 degree BTDC, had to unscrew the hidden 8mm screw to set to 12 degree BTDC and it worked. The timing is steady and doesn't jump around anymore.

5. Checking rpm with a dwell tach and it still jumping around from 500 - 800.

 

Please let me know what you guys think. And thanks for all your help.

[datzenmike]

Sounds all good now.

[sanyantho]

Thanks Mike, Hainz you hit it right on the money with your last post. I had to do the exact same :thumbup:

[banzai510(hainz)]

Well just to let you know the customer cam back and had point issues. I forgot to ajust the points. So I said fuck it he had a Pertronix on another dist. I said lets install this and be done with it.

Well I found a mount cause he forgot to grab the mount when he pulled this dist from junkyard. Why people do this I don't know.

well I had a spare and foundit I couldn't get it timed also either. would not go to the number one plug wire just by eyeballing it. The I flipped the timming plate over then I could get it all adjusted in fine.

I don't know How people fuck simple shit up !!!!!!!!!! I heard of the timming plates getting flipped before but I would not know why one would do this.

[banzai510(hainz)]

YOu should be able to get the dist timed from 0 -25 deg BTDC easily. if not you still may be off a tooth and compensating it by having the dist cranked with the timmin plateto one side.

 

but drive it up a hill and you have power than call it good.

 

if you have a photo of your point distributor cclose up shots and is a single point wit no ring above the point lobe you can convert to a Pertrinx ignition. But you still need the point coil and ballast resisitor.

 

there are" HOW TO" section on electronic ignition conversions. read up.  don't change  to another type of coil while running points. These will kill them.

 

I think your good for now.

[sanyantho]

Hi Everybody,

 

Here is a few pic of my work yesterday:

 

 

Why is my distributor shaft tang so off from the 11:25 position?

[datzenmike]

First... your bypass hose is folded closed. It's the one coming out of the side of your thermostat. Get a longer hose that will make a full loop before joining the metal pipe. This will improve your warm ups.

 

Also replace that broken thermostat cover bolt before you overheat and warp the head

 

 

 

 

Why is my distributor shaft tang so off from the 11:25 position?

If you set TDC just by lining up the cam lobes, I not surprised it appears to be out. The cam lobe position only confirm that you are on the compression stroke. Look at your crankshaft pulley and the timing scale behind it and move the TDC notch to the tip of the pointer. I think the L18 is just below the distributor.

 

If you are lined up, for absolutely sure at TDC, then the drive spindle for the oil pump and distributor has been removed and put in a tooth off. If it runs and ignition timing can be adjusted fine it's ok, just leave it. If you can't get the distributor to time properly then the spindle must be removed and moved to that 11:28 position.

[sanyantho]

Thanks Mike,

      I lined up TDC by putting my finger into the #1 spark plug hole and turning the pulley until I felt air pushing on my finger as well as ling up the first 2 cam lobes at 10 2 position, The timing mark is pointing to zero.

 

[banzai510(hainz)]

I think it looks fine what I see by the oil spindal

 

 

you might need a new lower water stat housing. now to swap the temp sensor over you might even crack it. best to find one intack from another motor and just take the 2 bolt out from the head. I now Mine all crack when I remove the temp sender. So I have spare lower temp housings and the new 16mm hex nut to hold the sender in.

 

 

if you gan take the rotor out to look at the point better I can see if you want to put a pertronix  in there  looks like a single point but need to see if the ring is above the point lobe otherwise the magnet ring in Pertronix kit will not fit on the point lobe cause the ring is in the way(needs to be machined off)