Questions on engine timing - '36 Dodge

I have recently replaced my distributor points base plate because of the stationary point's threaded hole being stripped out. (There has been a jamb nut system used on the stationary point for as long as I can remember. It is a real pain to adjust that way)!

I have carefully cleaned the minor storage corrosion from the new base plate and dressed the new point faces lightly. I am using the "new" condenser that came with the base plate also. I have set the point gap, best I can lightly feel, to .020 with a flat feeler gauge. All plugs are gapped to spec. There is a vacuum advance on this distributor along with centrifugal advance weights under the base plate. Part of the reasoning this was all done is two fold - hard starting especially when hot and a slight but regular miss or engine stutter at sustained high speeds (45mph or more) especially when hot.

I have tried to set the timing using a Sun 6 volt Timing Light, attached to the #1 cylinder, to the specified 4 deg after top dead center, but I can only get it to about 2 deg before TDC when it starts to lower the idle speed significantly and stumble. The timing started at about 14 deg BTDC.

I understand from the Service Manual that the timing can be set with a timing light to the indicated "Ignition Timing" from the specifications. The wording in the specification section reads: "Degrees of crankshaft rotation when points open" = 4 deg ATDC. The Service Manual also states that there is no need to disconnect the vacuum advance when using the timing light for this adjustment. If I were to push the timing down to the 4 deg ATDC the engine would stall for sure. As it is, I had to raise the idle speed at the carb a bit to keep it running at 2 deg BTDC. It also seems to have no power on acceleration while stationary. I have not done a test drive.

So, what am I doing wrong or what types of problems can I expect to try and locate considering this information?

Hi 1936 D2, I have just looked up 5 manuals for DBs from 1928 to 1938 and the all say 4 deg before TDC Hope this helps Ron

BEFORE! OK. Those are all different than my Service Manual that talks about AFTER.

I would be pretty close with where it is now then. I will just trim it up a bit closer to 4 deg BTDC and then do a road test. Thanks for all the time looking this up!

If anyone can tell me more how this "Ignition Timing" verses "Degrees of crankshaft rotation..." thing goes, feel free.

This is some info I have. I will not comment on it and profess to have no knowledge of the timing process. A little knowledge can be a dangerous thing....

Ross

Ross: The way that chart reads the timing is 4 degrees AFTER Top Dead Center! That agrees with my Service Manual. (But my car would run poorly at that setting). Hmmm... More info to come I hope!

Say "amigo"... If you are reading this, I wonder if you could check your car with a timing light connected to #1 cylinder and tell me what your timing reading is at idle. You mentioned in another post that your car starts easily with a "half crank". I am trying to go for that kind of set-up!

Like I said, I really don't know. Perhaps you have your engine installed upside down?

Seriously though, there must be an explanation if both your service manual and my book that I understood was some sort of bible for service staion mechanics of the day say the same thing.

Maybe one of the blokes on here that can lick a dipstick and tell you which cylinder is down on compression can shed some more light!

Even the "Motor's" manual says 4 lines after TDC. Couldn't be a typo! I would think it hard to adjust the distributor with the vacuum line hooked up,there's not much travel. I'm not sure that every engine responds exactly to specs.!

Try this trick.

Hook up a vacuum guage and adjust until you get the most vacuum then retard about 2 inches of mercury.

Works for me most times.

If you would like me to clarify with tect or pictures let me know, 1936 Dodge passenger car service manual states...........Piston position when points open .002 ATDC, all sorts of other info if you think it might help, cant remember if you said you had this manual or not sure which manual you are working from

I am working from the "Master Maintenance Manual" #D3497.

I am working from the "Master Maintenance Manual" #D3497.

Cant read the identification key on the cover of this book so that wont help, if the information I posted above is the same as what your book states than I guess I cant help, if its different than let me know

Ross: The way that chart reads the timing is 4 degrees AFTER Top Dead Center! That agrees with my Service Manual. (But my car would run poorly at that setting). Hmmm... More info to come I hope!

Say "amigo"... If you are reading this, I wonder if you could check your car with a timing light connected to #1 cylinder and tell me what your timing reading is at idle. You mentioned in another post that your car starts easily with a "half crank". I am trying to go for that kind of set-up!

Is that for static (engine off) timing? If so, then when you start the vacuum and mechanical advance units will advance the spark a fair amount even at slow idle. If you are setting by a test lamp while the engine is running and trying to get it back to 4 degrees after TDC then I can see where there could be an issue with it running correctly.

What Jason posted MAY be information for a static timing - like an engine rebuilder may use. I am trying to work off a timing light (since I have a decent one) on a live -sort of- running engine. That's why I am hoping "amigo" may be able to do the same test and give me a reading from an engine that is known to be apparently working well.

All the information seems to be contradictory (as is seen in this post). The issues of vacuum advance and centrifugal advance all coming into play on a running engine are the crux of the issue. Right now, I am thinking I should be somewhere around 12 to 14 degrees BEFORE TDC on the running engine (pretty much where I started). But then why is it so hard starting at that setting?

I must admit, I am a bit in a quandary at the BEFORE TDC info from Ron's five sources.

I will wait to hear more as this thread progresses.

IF an Engine was setup to fire after TDC (the piston being on the power stroke of the cycle) by the time combustion was completed the piston would be at the bottom of the stroke The reason for having detornation Before TDC is that as the piston reaches TDC on the power stroke the fuel-air mixture is already ignited and the full force of the explosion then forces the piston down again To have an engine timed to fire After TDC is a bit like closing the gate after the horse has bolted Cheers Ron

Ron: You are addressing the idea that the timing is applied to either a static engine or one that has no other advance features. With the distributor on the '36 having two advance features, both a vacuum and a centrifugal advance, there is advance working on the distributor all the time it is spinning or sometimes dependent on engine vacuum. I am trying to find specs that would allow me to set the timing via a timing light on a running engine. So at least centrifugal advance is working to some extent and vacuum advance to a lesser degree.

I understand what you are saying but we have to take in these other advance mechanisms when setting with a timing light. That is why I think they spec the 4 deg AFTER TDC. But like you say also, this MAY be a spec for a static engine, before the advances are applied.

Still trying to find out what the advance timing should be when these mechanisms come into play. Maybe like 12-14 degrees BEFORE TDC? That's what I need I guess.

...Still trying to find out what the advance timing should be when these mechanisms come into play. Maybe like 12-14 degrees BEFORE TDC? That's what I need I guess.

I wouldn't be surprised if it was close to the specs for the '36 Plymouth. For the '36-38 Plymouth the factory service manual has:

Mechanical advance:

0 degrees at 350 RPM

3 degrees at 400 RPM

6 degrees at 950 RPM

9 degrees at 1500 RPM

11 degrees at 1850 RPM

Vacuum Advance:

2 degrees with 6 3/4 in. of vacuum

11 degrees with 17 in. of vacuum

And, by the way, it shows the static (engine off timing) as 4 degrees A.T.D.C. The '36-38 Plymouth distributor is listed as a AutoLite IGS-4003-B-1 so you can see if that is the same as the Dodge.

There are some slight changes for those advance numbers in '42 when Plymouth got the 218 so a earlier Dodge might have slightly different specs especially if it has a 218 instead of a 201 engine.

Final edit: From the above numbers it looks like if you block off the vacuum advance and set the idle to about 500 then your timing light should show pretty close to TDC (a bit more than 3 degrees mechanical advance from your 4 degrees ATDC starting point).

Try this trick.

Hook up a vacuum guage and adjust until you get the most vacuum then retard about 2 inches of mercury.

Works for me most times.

Jack M has the right idea, you are much better off with a vacuum guage to get the best ignition timing. Dont get too excited with the 4 degree issue as this really is not relevant with todays fuels, the burn time characteristics are vastly different from the fuels of 1936.

What you really need to achieve is a steady vac. gauge reading of 18 - 20 inches at idle, this is accomplished by moving the distributor base plate, with the engine running, just as you do with the timing light.

If you dont have a vac guage, timing by ear will get you close to the mark. Set the distributor so that you get an easy start and a smooth idle; take the car out on the road and get into top gear, then steadily accelerate, if the car pulls away readily without any hesitation or pinging then you are in the ballpark, if it pings you are too far advanced and need to back the distributor off a little.

The final outcome should result in best acceleration just before the onset of pinging.

Having reached a satisfactory setting, then have a look with the timing light so that if there is a next time you know where to set things up.

Some great specific info from "ply33"s shop manual. The Dodge manual is not as "informational". Thanks.

Excellent explanation "hchris"! Very clear and good reasoning as to why to not worry too much about the indicated timing from the timing light.

I have a nice vacuum gauge so this should be fairly easy. I thought "JACK M" might have been on the right track!

:cool: Works on hot rods too !!

:cool: Works on hot rods too !!

It prob. grumbles throughout the whole ordeal

:cool: Works on hot rods too !!

No doubt in my mind, Jack has the best suggestion with a vac gauge but my Dad always did like hchris and set the timing by ear. Either way is probably better than trying to go by the book in this case unless that is what you feel most happy with. Sound advice given here in my view.

Ray

Yup. All good food for thought.

Guess I can close off this thread for now.

If I remember I will give a final report as to how the timing was finally set and what may have been causing the hard starting issues.

Too bad I have not heard back from "amigo" yet as to what his running timing looks like. Some day maybe.

Man I missed this post and now I need to. Know I got my engin back and want to install the oil pump but don't know where to start

I find this question very interesting ... Following my distributor problems 540 kms. from home last year.... I had another distributor re built .. Carby over hauled .. new fuel pump installed and a new exhaust system fitted. I also set the timing as discribed by 1936 D2 .... using the service manual standards.

I found the car ran OK for about half an hour on the road, and then had afterfire in the exhaust on decelleration and when backing up or moving slowly .. I fiddled with the adjustments and succeded to destroy a muffler that had done less than 200 kms. I had a friend come and have a look during this last week, before I took the step of removing the motor . .... He set the timing well advanced so the timing light was showing a little more than 15 deg. before TDC with vac pipe attached. I was doubtful of this much advance but ran the motor for 2 hours in the garage before going for 2 1/2 hour drive. car ran excellent and I have had it out twice since then without problem ... I am not overly mechanicaly knowlegable. but I was sure I had it set "by the book " ... All I can suggest it give it a try a fair bit advanced..... It seemed to work on mine

1936 D2,

I recently did the timing on my 1935 Dodge. For starters, you mentioned something about hard starting when hot. Does it crank over slowly when hot?...If I were to guess, this is a symptom of timing that is too far advanced during cranking speed. My timing was set at 2 deg ATDC and I have no problems with start ups, cold or hot. Let me just list a brief summary of timing in degrees vs engine speed, then explain...

350 Rpm - Cranking speed - mechanical advance activated slightly, & should advance timing 1 deg to 3 deg.

800 Rpm - Idle speed - mechanical advance activated & should advance timing to about 6 deg BTDC.

3000 Rpm - High Speed - mechanical advance, vacuum advance activated & should advance timing to about 24 deg BTDC.

Explanation:

350 Rpm - During cranking speed, mechanical advance should put timing at 0deg TDC or AFTER. This is important because why would you want your poor little

starter fighting against violent explosions in the combustion chamber? Power stroke on these engines should be at TDC or

after TDC (ignition while the piston is on its way going down!). STATIC TIMING MUST BE SET 1st

With the engine NOT running, put your crank at 2 deg ATDC, pull #1 plug out, wire still attached to plug, turn distributor ccw until

spark occurs at the plug...presto. Static timing is set. Now during cranking, mechanical advance is activated & should put power

stroke @ TDC or later.

800 Rpm - Mechanical advance is activated at start up. The faster the distributor spins the harder mechanical advance works. Higher engine speed means

more advanced timing because air flow is SLOW compared to piston speed & spark speed. (Don't know how else to put it..Ha!)

3000 Rpm - Mechanical advance and vacuum advance is activated. These combined timing advancing mechanism are causing max timing advance. Make sure

your vacuum advance hose is attached to PORT VACUUM and not MANIFOLD VACUUM. Port vacuum is a vacuum that occurs above the throttle

plate (above idle). Manifold vacuum is a vacuum that occurs below the throttle plate (Idle).

Hope this clears things up and helps. I am not an expert, but always willing to offer insight if I have any. I'd be glad to hear of any news of progress on this issue.

Good Luck,

Thomas

I could use some help setting my timing with the vacuum gauge method mentioned above. When I connect my gauge as shown in the picture I get almost no vacuum at idle. If I crack the throttle the vacuum goes right up. 

Is this his the correct place to check the vacuum?  This is where the windshield wiper motor hooks up. There is a copper vacuum line to the distributor which connects opposite to this and closer to the manifold.  From what the previous post stated it seems these lines may be installed backwards. 

Jim

48 minutes ago, jimy said:

it seems these lines may be installed backwards. 

Yes,backwards ...the distributor is almost always hooked to a port "above" the throttle plate.  The wipers are hooked to direct unported vacuum source.

Agreed, the vac source for timing should be from the manifold not the carb, in airflow terms it should be down stream of the throttle plate.

At idle, with good compression, you should see about 18" of vacuum; if not move the distributor either way until you achieve this.

You may find the vac can go a little higher with distributor movement, ideally you should set it about 1 -  2" below the maximum value achievable; in a perfect world this should give you optimum timing.

Thanks for the help.  By the way - is the 18" of vacuum specific to this engine or to a particular compression ratio, displacement, etc?

I'm anxious to try this out, but the old copper line is too short and I had trouble finding correct fittings that would allow a rubber line for at least testing.  Turns out the current line (likely a brake line ) wasn't sealing at the distributor end anyways (line was still rattling around when fitting was tight).  So I am waiting for JB Weld to dry where I bonded a stub of brake line onto the fitting.  Then I'll run the rubber line and see how it runs.

Jim