Points and dwell setting

[sockpatty]

So I went out and bought me a actron multimeter with dwell and tach so I could do my own points in the future. I had them set by my buddy but the boat still ran like crap.
So I put the dwell on it and it said 25. The book says it should be between 28 and 34. So I checked the point gap and it was set at .022 which is what the book says it should be. So I dropped the gap twice to 20 and then 18. 18 landed me at 30.

So did I do that right? The boat seems to be running good in the driveway.

I hate point and will be going to est next year.

 

[kenny nunez]

Dwell short cut. Remove the spark plugs, be sure to ground the coil wire, spin the engine and adjust the dwell , Forget using a feeler gauge. Also if the dwell moves a lot when the engine is running the distributor needs to be removed and a bushing needs to be installed at the bottom of the housing.

 

[sockpatty]

Didn't know I could do that. I was setting and putting back together and then running it to check. Numbers seemed alright.

 

[Oshkosh1]

You're fine.

FYI; An engine which is designed/curved to run on points will make more power on them than running one of the Pertronix/Accuspark modules(confirmed by dyno pulls). I still run points on a couple of my vintage cars and other than looking at them every 5-6k miles they're no trouble at all.

Also, timing/advance will change depending on fuel formulations. Today's fuel burns differently from the fuel the engine was originally designed with. Use the book as a starting point and fine tune by ear/reading plugs/"butt" dyno".

 

[stonyloam]

Dwell is simply the duration that the points are closed expressed in degrees of rotation of the distributor cam. This is the time that current flows through the coil "charging" it. If the dwell is too short the coil will not be able to develop full voltage, if too long the coil can overheat due to too much current flow. The gap is not important and can be affected by a worn cam or cam follower, and is useful for the initial setting only. So you can ignore the gap, as long as the dwell is correct you are OK. Since the dwell setting affects when the points open you will need to reset the timing once the dwell is set.

 

[achris]

Also, changing the gap/dwell will change the spark timing. If you move the points, you must check/adjust the timing.... (Increasing the gap/decreasing the dwell will advance the timing... Decreasing the gap/increasing the dwell will retard the timing)...

Chris...........

 

[sockpatty]

Ah man,really. I thought I was done. Since I don't know crap about timing, I'm gonna have to find someone to do the reset. The book I have is not very clear on it.

 

[sockpatty]

I watched a YouTube video on how to use the dwell.

 

[achris]

Adjusting the timing is easier that the dwell. Get yourself a timing light, hook it into #1 spark plug lead, identify the timing mark on the front pulley and timing cover. Run the engine at idle, point the flashing timing light at the marks and see what is reading. If the timing needs to be adjusted, loosen the distributor clamp bolt and rotate the distributor slightly until the marks align where you need them to. When you're finished, tighten the bolt and recheck the timing. If it hasn't moved disconnect the timing light. Took longer to write this description than it does to time an engine.

Chris. ...

 

[sockpatty]

That does sound easy. I'll get me a timing light after work tomorrow. Thanks for the info guys.

 

[achris]

One more thing. As you alter the timing, the engine idle speed will change, so adjust that back to the spec after you move the timing. Then recheck the timing.

 

[Oshkosh1]

Your "all in"(fully advanced) timing should be roughly twice your base. So if you're happy with 18? base(under 2kRPM), at higher RPM(over 3k) should roughly be 36?. Don't get concerned if it's not dead on but if it's not close you'll need to look at your advance mechanism(s)

Don't even concern yourself with dwell. Gap the points and run it.

Back in "the day" the only thing you needed for a tune up in most cars running points was a matchbook. The single thickness of the cover is approx .016"(to gap the points while cleaning them) and folded over it was roughly .030" which is close enough for most non electronic ignition plug gaps.

I rebuild/tune old British car engines and also re-curve the dizzy's to run well on new formulations of fuel. I've never had a single person need to use a dwell meter yet. Point gap will get you close enough for our purposes, if not there's something amiss...

 

[Lou C]

Ah yes this reminds me of the fun of setting points, and trying to reconcile the gap vs dwell, and how much we liked the GM Delco distributors that had:
​1) a little metal window you could open to insert an allen wrench to adjust dwell with the engine running, much easier
​2) they came up with a unitary points/condenser set up where they were both mounted to the same plate, again easier than the competition.

​Having Chevrolet small blocks it was sure nice being able to adjust the dwell with the flex allen wrench set up seeing as how the dist was way back in the rear of the engine. Even easier on Cads, and Buicks with the same style dist mounted up front....

​I still have points in my ancient 4.3....

 

[sockpatty]

So let's say someone twisted the cap too much due to have really strong forearms and can't get it start due to timing being so off. How would one go about getting it back on track. It was going hood up til the turn.

 

[achris]

Ok, using a dwell meter is the best way to set the points. Using feeler gauges to get you close is just that, close. The dwell angle is measured electrically, and is far more accurate. Here's a picture of what your timing curve will look like. You can't change the curve (not easiely anyway), so you have what you have. Total advance is 36?, initial advance is 8?.



Ok, what to do when the distributor has been moved too far for the engine to start....

Turn the engine by hand until the timing marks line up for the engine to fire on #1 cylinder. Remove the distributor cap, loosen the clamp bolt and turn the distributor until the points are just about to open. Slightly tighten the clamp bolt and start the engine. Now go through the timing procedure with a timing light.

Chris........

 

[sockpatty]

Thanks. I got it started again. It's hard starting and idles for crap. It doesn't want to stay running lower then 1100. I'm giving up. I'm gonna bring the boat on tomorrow and have them fix the issues. But at least my dwell is good. Thanks for the help guys.

 

[stonyloam]

If you want to give it one more try. Try adjusting the idle mixture screw on bottom part of the carb body. Gently turn it all the way in until it bottoms (do not force it), then back it out 1 1/2 turns. If it starts and runs, adjust it in until it begins to stumble, then out until it stumbles. Back in until your rpm peaks. Might help. Sounds like your timing may still be off, might be a bit retarded.

 

[sockpatty]

Yeah I tried that while it was running. I'm sure my neighbors are sick of me running the boat in my driveway. There nice people so o don't want to **** them off. I've got all next week off and I want to be on lake Michigan with my kids all week.

 

[sockpatty]

But on a side note,I am acquiring tools to be able to do all this stuff. I was proud of myself when I aligned the engine. Simple,yes. But still it was my first time. Got the alighnment tool off Craigslist for 20.

 

[Oshkosh1]

I'm going to tell you what I tell most people tuning their vintage(points) car; Ditch the timing light and tune by feel. Advance it until it runs smoothly...keep advancing it until it starts to stutter a little and then just turn it back a bit...tighten it down and run it. I've LONG lost count of the number of people I've helped who have had MUCH more success after they ditched the light. NONE of them have suffered the ill affects of over advanced spark. Tuning to a number is foolish. Too many variables between individual boats/engines. Once it runs well...THEN hit it with a light to record and save for future reference. I've had cars in which the base timing was off by 8-10deg over "spec" from a manual written 40+ years ago. Fuel, timing chain tension, dizzy spring/weight issues all contribute to your timing numbers changing drastically over "new" spec.

Read your plugs after a good run...those will give you a TRUE sense of what's going on with YOUR specific powerplant...