Voltage at (-) side of coil?

[SSTKO81]

Re: Voltage at (-) side of coil?

Up to this point timing has been roughed in using TDC method. I realize its crude, but untill I can get it to stay running for 5 minutes, it's my best option. Dwell (gap in this particular case) was dialed in using a .030 feeler guage. (looks like thats at least .010 too much)
What exactly does dwell dictate? How long the points stay open?

 

[HT32BSX115]

Re: Voltage at (-) side of coil?

I'm gonna disagree with you Rick. Gap get's it close enough to run.

I'm not saying that setting dwell is not a good thing to do, I'm just saying that it's not a show stopper to set the gap and run it.


Millions of different engines are out there running having never had the dwell set and are "no worse for wear".

2 examples I can think of are both my former OMC 460 and my former 150 Mercruiser(GM inline-6) They NEVER had the dwell set and both ran fine.

Might it have been better to set/check dwell on either? no question. but it wasn't absolutely necessary. My 292 ford Y-block ran for thousands of miles and never had the dwell set or checked.

I would still get the "big stuff" dialed in before fine tuning the dwell etc...

 

[amdburner]

Re: Voltage at (-) side of coil?

Dwell (gap in this particular case) was dialed in using a .030 feeler guage.

.030 is too much gap and will give you too little dwell. Start around .020 and see how that goes. What I did to get my timing close was to set the timing mark on the balancer to the zero mark on the timing indicator and then use a multimeter set on continuity so that it would beep when the points were closed. I then would turn the crankshaft back and forth with a tool on the water pump pulley until I had the distributor set for the points to open at 6 degrees BTDC. I then fired up the engine and discovered that my timing light was fubar.

Anyway, I purchased an Actron automotive diagnostic multimeter and a new dial-back-to-zero timing light and fine tuned the dwell and timing with them. The engine now starts easy and runs very smooth compared to what it did prior. Unfortunately I haven't had a chance to put it back in the water this week.

 

[bruceb58]

Re: Voltage at (-) side of coil?

Up to this point timing has been roughed in using TDC method.

That's not a good method. You can still set the timing without the engine running with a timing light. You just have a helper crank the engine and use the timing light as if the engine is running.

 

[carcraze]

Re: Voltage at (-) side of coil?

As I understand it (it's been a while), gap and dwell in the end affect timing because the points breaking the coil circuit is what fires the coil. Changing the gap which is what you change for dwell affects when in the rotation the coil fires.

The reason to check the dwell is the points have to stay closed long enough to fully saturate the coils magnetic feild, as the collapse of this feild is what generates the high voltage spark.

Gapping the points should get it close enough to run as long as the timing has been set either as above by cranking the motor and checking with the light or in the past I have used an ohm meter hooked up to the points to determine when they open and can roll the distributor with the engine set on the proper timing marks for cyl 1.

 

[SSTKO81]

Re: Voltage at (-) side of coil?

Ok, so first thing tomorrow morning I'll do the following:
1: Set the gap on the points to under .020 and be sure to fine tune dwell ASAP

2: Make sure timing is accurate

3: Make sure Carb is indexed correctly and not starving.

And I'll let you all know how that goes and probably be coming back with more questions. Thanks a ton guys.

 

[JustJason]

Re: Voltage at (-) side of coil?

I'm just saying that it's not a show stopper to set the gap and run it.

I think it's more of an engine specific thing as to how critical dwell needs to be vs gap. For instance, I was working on yet another Volvo AQ131A today (seems i'm the old volvo guy lately). I eyeballed my gap then hooked up the dwell meter. Spec is 59 +-3, my eyeball gave me 70 degrees on the meter. It coughed and spit and would not run. Fine tuned it down to 60 degrees, smooth as silk. That's all it took. That and me holding a gun to the solex carb!!

 

[SSTKO81]

Re: Voltage at (-) side of coil?

Also, If this is a fuel related problem as well its most likely due to bad initial settings on my carb (2G Rochester) Is there an initial setting that works better for these than what the manual recomends? I've got it set to all factory specs right now; but what the factory thinks verses what y'all know is two different things.

 

[SSTKO81]

Re: Voltage at (-) side of coil?

And as promised;more questions. How do I set the timing when there are no markings the balancer? There's a small notch on the end of the crank, but nothing else anywhere. could this be an index mark?

 

[bruceb58]

Re: Voltage at (-) side of coil?

You said before that you set your timing with a TDC method(whatever that is). What did you use then?

Does the balancer have a single line on it?

Might want to post a picture.

 

[SSTKO81]

Re: Voltage at (-) side of coil?

Well big news! She fired up. I Went ahead and closed the point gap down to about .018 and retarded the timing back a hair just to start with. And after a little cranking she came to life. Turns out my timing was off only by about 4*. -not bad for practically shooting in the dark! But I wanted to give you all a big thank you for your wisdom and insight. It's gonna be a great weekend at the lake now