Timing Advance?

[atkinson40]

Hooked up a vacuum pump to the dizzy advance and verified that the timing was advancing with a timing light as I applied vacuum to the port. Hooked up a vacuum meter to the carb port that provides vacuum advance to the dizzy and can see that at idle there is no vacuum on this port. There's only vacuum when I rev the engine. Is this correct? That would mean the port opening inside the carb is only exposed to the downdraft of the carb when it's rev'd up or that at idle the downdraft is so small as to not cause a vacuum at the port. -K

[datzenmike]

That is normal and is an emission thing. There is a vacuum port above the throttle plate when properly set at idle. Above the plate reads zero vacuum as it is exposed to outside atmospheric pressure, but when the throttle is opened the plate lifts up and exposes the port to intake vacuum.

[atkinson40]

Thanks DM. My timing light seems to have crapped out. So my diagnostic tools are now reduced to a vacuum meter. From the interwebs, I see I can set the idle mixture with a vacuum gauge and also the timing. I'm left with setting the idle w/o an RPM meter. Any way to do this? -K

 

PS: It's raining in San Diego in May. In 35 years I've lived here this has never happened. Mind you I'm not complaining. I wish it would rain at least once or twice a month all year long. This is a desert after all and my 100 fruit trees need the water, but WTF are we doing to our climate?

[DanielC]

this could be about your Datsun, your Toyota, or your Honda. I am thinking that since this is a Datsun forum, it is your Datsun pickup. But even assuming that, it could be a 521 truck in 1972, or the 620. The model change was made mid year.

Does the truck have the original engine? Does the engine have the original carburetor? Does the engine have the original distributer?

 

If your vacuum advance works, and the centrifugal advance works, you can set the timing pretty close with just a test light. Hook the test light to ground, and the negative side of the coil. Turn the engine in its normal direction, by hand, WITH THE SPARK PLUG WIRES DISCONNECTED. The light will be off before the spark should happen, and exactly when the light comes on, you should be passing the correct timing mark on the crankshaft pulley. This method will work with points, but may not work with an electronic distributer. Go for a test drive, and listen for spark knock. If it knocks, retard the timing about two degrees, and test again. If it does not knock, advance the timing about two degrees, and test it again.

 

If your idle speed is too low, the engine will die easily in normal driving. If it is set too high, the engine may have a tendency to keep running after the key is turned off. Compare the idle to your other cars. Does it seem much faster, or slower? It probably is.

[banzai510(hainz)]

I dont have a RPM meter. Just set it to 10 on timming lights and go between the carb mixture and the timming light(dizzy timming)

[atkinson40]

Thanks DC. The Pu is a '72 620. Motor swapped to an 1.8. Still has points. Is the test light just a 12V bulb? I tried timing/mixture using a vacuum gauge yesterday and failed. Must have something else wrong. I think I read somewhere the vacuum should be steady 16-20 and I can get it there with various setting of timing and mixture, but I don't think those settings are correct. I'll try the bulb method if I can't get my timing light to work. Thanks -K

[DanielC]

you can use just your common everyday test light. With points, it is easy. All the points do is connect the negative side of the coil to ground. The spark plug fires when the points open, breaking the circuit. So, when the points open, the light comes on.

 

Here is a site with lots of information about your truck.

http://www.olddatsuns.com/

[banzai510(hainz)]

Is the test light just a 12V bulb?

 

whats this going to ck. Thats the point work? Just grab the output of the coil and place to ground and your see spark when you start . but you know it sparks. You need the timming light.

Time it with no vac adv hose hooked up. Personally I do both and dont notice much change.

 

If your timming is really fucked then I would swap anynother dizzy. ,I had one where my weights and springs exploded in side and was draggin around. Or ck if a wore out bushing which cause the point bounce(dizzy shaft wiggles side to side cause points to open)

[DanielC]

You slowly turn the engine in its normal direction with the test light hooked up as I said, and you can see if the light goes on when the correct mark on the crankshaft pulley passes the timing pointer. If it does, your timing is pretty close to where it should be. You can use a timing light to get an exact number, but I generally advance the timing on old non computer engines until they knock slightly, and then retard the timing about 2 degrees any way.

[atkinson40]

Or ck if a wore out bushing which cause the point bounce(dizzy shaft wiggles side to side cause points to open)

 

I can see my dizzy wobbling around. The cap is doing a dance. Is this going to cause it to FU? Can I fix this with a bushing? I've got an electronic dizzy I snagged at the JY a while back but don't have the souped up coil or the electronic unit I need to go with it. I think there are aftermarket things I could find and use for those two things if I need to. -K

[banzai510(hainz)]

I can see my dizzy wobbling around. The cap is doing a dance. Is this going to cause it to FU?

 

Only you can tell if its really loose. or not.

[ggzilla]

Yes, if your distributor is moving around, you won't be able to set the timing correctly. Tighten the hold-down bolt.

 

If the shaft is worn, your timing advance will never be correct. Even worse, if yuo have a points distributor, you'll never be able to set the point gap correctly.

 

If you have an electronic distributor, you don't need a timing light or a 12V test light. Just turn the crank so the timing mark is at 7 or 10 BTDC and then rotate the distibutor to align the teeth inside. That's it.

[banzai510(hainz)]

If you have an electronic distributor, you don't need a timing light or a 12V test light. Just turn the crank so the timing mark is at 7 or 10 BTDC and then rotate the distibutor to align the teeth inside. That's it.

 

Cheater!!!!!!!!!!!!!!!!!!!!!!!!!

[atkinson40]

If you have an electronic distributor, you don't need a timing light or a 12V test light. Just turn the crank so the timing mark is at 7 or 10 BTDC and then rotate the distibutor to align the teeth inside. That's it.

 

Cheater!!!!!!!!!!!!!!!!!!!!!!!!!

 

 

Points

[atkinson40]

Yes, if your distributor is moving around, you won't be able to set the timing correctly. Tighten the hold-down bolt.

 

If the shaft is worn, your timing advance will never be correct. Even worse, if yuo have a points distributor, you'll never be able to set the point gap correctly.

 

If you have an electronic distributor, you don't need a timing light or a 12V test light. Just turn the crank so the timing mark is at 7 or 10 BTDC and then rotate the distibutor to align the teeth inside. That's it.

 

Bolt is tight but my dizzy is still wobbling. I banged my timing light until it started working again and set the timing to 10 Degrees BTDC. I can see the advance working when I rev the engine. Bad news: Every once in a while the timing light misses a beat on all plug wires. This coincides with a slight stutter in the engine. With the engine off I can grab the dizzy body and move it around side to side. -K

 

[atkinson40]

First time I tore this pony apart I had an extra O ring that I couldn't place. I posted and someone said it looked like the dizzy o ring. I didn't remember it coming out when I removed the dizzy so I didn't pay too much attention.

 

Now maybe I'll rethink that. I see a bit of oil seepage around the dizzy. Where would this o ring go and could it missing be the cause of my dizzy wobble?

 

When I get back from Mexico this afternoon I'll see if I can track down the o ring, pull the dizzy, and see where it could fit.

 

-K

 

[DanielC]

It goes together like this. Distributer, steel plate held to distributer, using a bolt with a 8 MM head, up into distributer body, "O" ring over distributer, next to steel plate, distributer into mount on engine, and a bolt with a 10 MM head down into distributer mount, through steel plate.

[banzai510(hainz)]

when I mention dizzy wiggle I was talking about the shaft inside where the points are. But i think you knew this already.

If outside wiggles I would look into this also.

YOur a L16 guy you should have 2 to 3 spare FREE dizzys lying around for spare or trouble shooting.

 

but if you need a spare dizzy take the old one out put a FREE sign in the yard. In the morning there will be a couple more next to it and pick another one to install.

[atkinson40]

It goes together like this. Distributer, steel plate held to distributer, using a bolt with a 8 MM head, up into distributer body, "O" ring over distributer, next to steel plate, distributer into mount on engine, and a bolt with a 10 MM head down into distributer mount, through steel plate.

 

 

Thanks DC, Will check after return from Mexico this afternoon. -K

[atkinson40]

Anybody have a picture of what the dizzy should look like in this image? I've never been happy with the way the points set. Right now the points don't follow the cam lobe on the shaft for the whole revolution. They just get bumped open on the high part of the cam. I'm thinking my wobble is coming from this bump is banging the dizzy over. Everything seems tight and I have an o ring where it should be. -K

 

[ggzilla]

It is normal to not ride on the cam at the low spots. The distributor wobble is not normal.

[atkinson40]

It is normal to not ride on the cam at the low spots. The distributor wobble is not normal.

 

 

Thanks GG. Does the points set up look normal. That adjustment slot and the way they sit doesn't seem right. Do I have the right set of points? Or do I have them installed wrong somehow? -K

 

I'll keep looking for the dizzy wobble source.

[banzai510(hainz)]

I would swap in another dizzy from somebody. Those point lobes should have point grease on there also.

 

most O rings that come in the Felpro kit or most kits go in the dizzy pedastal. youll pull the dizzy from the Pedastal and it fit inside to keep oil from oozing out the top

[atkinson40]

I would swap in another dizzy from somebody. Those point lobes should have point grease on there also.

 

most O rings that come in the Felpro kit or most kits go in the dizzy pedastal. youll pull the dizzy from the Pedastal and it fit inside to keep oil from oozing out the top

 

Don't have somebody else. :(

[banzai510(hainz)]

If you were closer I give you 2 as my pile is getting to big!!!!!!