Chrysler model 65, 1929 correct dwell angle for modern petrol

[aron_budapest]

Could somebody know the good ignition dwell angle for my flathead six normal compression (not red top)? I want to adjust it by timing light.  Better if i know the dwell at idle speed , mid range rev and high rev to check the automatic adjust weights are working properly. I live in central europe and use unleaded 95octane fuel. Thanks

Edited March 24, 2022 by aron_budapest (see edit history)

[maok]

You adjust the points gap (standard is 0.020") to adjust dwell angle, you should aim for around 38. 

 

Timing light is generally to check the timing to advance/retard the timing, turn distributor clockwise to retard and anticlockwise to advance.

[ryan95]

If I am wrong, I hope someone corrects me. I think that the dwell angle spec should be about the same for any six cylinder engine that uses a typical coil and distributor setup. Dwell is just how long the points stay closed, which it's how the ignition coil builds enough of a charge for good spark. This means that if the point gap is too wide, the dwell time won't be enough. The specified point gap is usually what gets the dwell about right, but setting the point gap based on the dwell is probably better if you have a meter and know what to shoot for. Make sure to set the timing after getting all of that correct since changing the point gap doesn't just change how wide they open, but also when the points open. 

[m-mman]

1 hour ago, ryan95 said:

If I am wrong, I hope someone corrects me.

Nope this is correct. 

The Point gap (also known as dwell) is set to the correct numbers and left there. 

If the point gap (dwell) is wrong it can affect the timing BUT you do NOT ever adjust the point gap to adjust or correct the timing!   

 

First set the points. (gap and/or dwell) THEN you turn and adjust the distributor to set the timing. Either to original specifications or making adjustments for fuel quality, operating environment (high altitude?) or best on the road performance. 

[Bloo]

1 hour ago, m-mman said:

First set the points. (gap and/or dwell) THEN you turn and adjust the distributor to set the timing. Either to original specifications or making adjustments for fuel quality, operating environment (high altitude?) or best on the road performance. 

 

This is the correct way.

 

5 hours ago, aron_budapest said:

Better if i know the dwell at idle speed , mid range rev and high rev to check the automatic adjust weights are working properly.

 

Dwell may change with RPM, but that is just a coincidence. It won't tell you if the weights work properly. Those adjust timing automatically with increasing RPM, and to check them you need a "dial back" style timing light, or timing tape on the front pulley and a standard timing light, or a distributor machine.

 

5 hours ago, aron_budapest said:

I live in central europe and use unleaded 95octane fuel.

 

It is timing advance, not dwell that might change for higher octane. You should be fine with the stock setting, but I might try 3 more degrees of timing and see how it runs. If it's fine, I might try another three. higher octane fuel often allows a little more timing advance, and more timing advance will make a little extra power.

 

Potential problems from too much timing advance are pinging or detonation, an uneven miss either idling or revved up in neutral, trouble starting because the engine "chugs" or tries to kick back on itself, or trouble getting the idle speed set right.

 

Edited March 25, 2022 by Bloo (see edit history)

[aron_budapest]

Sorry I think I put it wrong, my english is not the best unfortunatelly.The question is how many degree need the timing adjust for modern petrol.I use pertronix electric ignition, so no points and gaps which I can measure. 

[edinmass]

You can have the correct point gap, and the dwell can still be a mile off. It’s especially noticeable on dual point set up’s. In my experience today about 80 percent of the cars have incorrect points in them......thus the gap may be fine, but the dwell and synchronization can still be a mile off. Today more than ever....put your distributor on a Sun tester and run it up to speed. Checking the advance curve is very important as many are gummed up and don’t function. Also, running it to a high rpm you can check for arcing, and also shaft wobble.....another common problem.

[maok]

1 hour ago, aron_budapest said:

Sorry I think I put it wrong, my english is not the best unfortunatelly.The question is how many degree need the timing adjust for modern petrol.I use pertronix electric ignition, so no points and gaps which I can measure. 

IIRC it's about 2* btdc standard, but as mentioned, keep advancing until you experience knocking from the engine then retard back a couple of degrees. You can probably get to 10* btdc without knocking.

 

The problem you may experience is on starter motor pinion and flywheel gear with original Bendix style of starter motor on your  car

[aron_budapest]

Sun tester unfortunatelly not available here in hungary.I take the distributor apart, clean it, bushing and everything is fine.Weights are moving freely, springs are ok.As I mentioned an electric pertronix ignition installed.There is a mark in the crankshaft pulley and the engine front.This could be the ignition point at idle? When I increase rev I see the weight advance is working well.

[ryan95]

Keep all of the parts you removed with the points in case you decide to go back. Points are reliable, fixable, and parts are plentiful. I work on boats during the warmer months. Of the two boats that I work on with Pertronix units, both boats have had a Pertronix unit fail, requiring ordering another and waiting for it to arrive. The only instance I would use a pertronix is if I had a worn distributor bushing and was too lazy to fix it.

[edinmass]

Take the Pertronix out........nothing but headache..........run it stock.

[maok]

Nothing wrong with the Pertronix, keep it and enjoy points free motoring...:)

[keithb7]

All this talk about points and dwell. 
 

My ‘38 Chrysler, I can set the timing to the point where the engine pings under load. I back it off. Then no pinging. 251 ci 25” engine. 
 

My ‘38 Plymouth, I just rebuilt the engine this past winter. I can play with the timing. All over the map. It will certainly buck a bit and feel poor if timing if off, but It doesn’t seem ever ping under load.  237 ci 25” engine. 
 

Wondering why the difference? Same octane gas. Maybe the older, not freshly rebuilt engine has carbon build up?  Would that make a difference?

Edited March 26, 2022 by keithb7 (see edit history)

[aron_budapest]

I keep all the original parts, they are in a box under the rear seat, so I can put it back if electric unit fails.

 

[Flivverking]

Dwell was not a major concern back in  the day..as long as there is enough. 

 If everything is in good condition,set up close to spec.  and you don't have a fxxked up worn distributor cam,regardless of fuel,you should be o.k.

[Tonz]

I remember in my youth with or first cars, they were usually 10 to 20 year old bombs that we always had to work on. This included tune ups. We were all just setting points at 16 or 20th.

Then in the 80s, young smarty apprentice mechanics started to tell us we were all wrong, our cars weren't running correct because of the "dwell".

Yep, bluffed a lots of people out of $$$ for a "dwell" tuneup.😆

[Rusty_OToole]

I worked on a lot of sixties cars. The repair manuals gave points gap and dwell. I often set the gap with a feeler gauge then double checked with a dwell meter while setting the idle speed. They were always spot on, or no more than a degree or two different. In other words both methods gave the same result.