underhood heat

[Glenwood]

Thank you for the detailed info. I've been reading up on this subject quite a bit lately at nauseum! (OCD as my wife calls it). After numerous attempts to tune, I realized there are other contributing factors that are likely causing my issues. Many have pointed out the missing shroud as a main source of the heating problem, but I feel that while a shroud is essential to maximizing cooling efficiency, the root cause lies in the ignition/timing system. With issues in this area, the engine is not running well and causes some overheating that is magnified by the hot outside temperature at the time; which in turn affects the fuel in the eddy and so on.
So where am I at?
Well, it is difficult to determine exactly where the issue lies. I suspect the coil primary circuit being starved for voltage and/or increased resistance as it heats up all leading to a reduction in output voltage and possible erratic behaviour. This may be why only some spark plugs appear to be black from running rich.
Here are my findings:
ballast resistor 1.6ohms at room temperature
Coil: accel super stock
primary 1.5ohms cold, 2ohms when (very) hot
secondary 10.3kohms cold, 12.9kohms (very) hot

key on-not running
voltage to ballast 11.39V (to ground)
from ballast 6.45V to ground (suggests a drop of 4.94V & current of 3.09A)
Measuring to ground is not accurate however, as this is a closed circuit. Measuring to the neg side of the coil:
Across the coil: 5.37V. At 1.5ohms, the current is 3.36A. This means that the voltage drop across the BR is actually 5.38V. Total voltage applied from the orange box is 10.75V.

Running at 2000rpm (engine still warming up)
Voltage across coil is now 3.4V which drops the current to 2.27A and a vdrop across the BR of 3.63V, meaning total voltage applied from the orange box is now only 7.03V.
I'm not sure if these voltages are normal, but they seem low to me. I think the BR is too high causing to much of a vdrop and should be reduced. However, I cannot find specific details on how much current this circuit should have. I'm thinking that I have to buy a new coil and BR if required. But which coil to buy? So many choices...

The suspected low voltage of 11.39V to the BR led me to discover that the charging circuit has failed. The constant output voltage regulator is supplying about 10V to the alternator field, but the output from the alt is 36V! With a load applied, the voltage dropped to 22V. I'm guessing the alt diodes are fried and the VR may also be cooked from the long trip I took. I plan to take the alt for testing to a local shop after a few more tests of my own.

 

[Don Gould]

Quick and easy fix for good

 

[threewood]

I hope you get it straightened out. How did the alt test out?
Another ignition option is Pertronix. I have 2 and they work great. Uses the solid state black ign box, Flamethrower coil and drop in module so you keep your stock distributor. Only one extra wire. And you can bypass the ballast with this setup as the coil needs full 12v.

 

[Glenwood]

I pulled the alternator and the auto electric shop spun it and said it was a good and strong 75A putting out 19v.
I told him that my meter is reading 36-39v but he said that can't be. Hmm... my fluke usually is pretty accurate so what am i missing?
Re-installed and tested again.

 

[Glenwood]

Installed a new vr and still not charging wtf? All devices are externally connected to ground wires so that's not it. The vr is sending 10+ volts to the alt field and 39v output but only 12.4 at the battery. Weird

 

[Glenwood]

So, the engine starts easy and runs well despite the charging issue until it is at temperature.
I bypassed the br so the coil at 1.5ohms is getting 8-9v. Then the coil gets hot again reaching 150-160F and the engine starts lacking power and doesn't rev well.
Primary resistance reaches 2.1ohms, secondary reaches 13kohms. I think the spark gets weaker as the coil heats up.

So i threw another stock coil on while the engine was still warm that tests prim 1.4ohms, sec 8.8kohms cold. Immediately runs better with losts of power. After running for 10 minutes the coil reached about 120F and the resistance increased to 2ohms/11.8kohms. I think that proves the coil is crap.

 

[Glenwood]

I hope you get it straightened out. How did the alt test out?
Another ignition option is Pertronix. I have 2 and they work great. Uses the solid state black ign box, Flamethrower coil and drop in module so you keep your stock distributor. Only one extra wire. And you can bypass the ballast with this setup as the coil needs full 12v.

I think an aftermarket system is in my future. First i need to figure out this charging issue.

 

[ckessel]

Very informative read here with the info from Don and your diagnosing Glenwood.

 

[miller]

Yeah, I kinda suspected the coil, being at least part of the problem.

Don't take this wrong, thought about mentioning before, but when you gave the compression readings, personally think there's too much of a spread. All should be within 10% max. What can be done about that? Not much...maybe after time, the gap will close. Big reason your plugs are showing difference.

I think an aftermarket system is in my future. First i need to figure out this charging issue.

Yes on the charging issue, maybe check wiring too?
Choices on the ignition system, plenty of them. You probably already know what I have, pure old school...stock coil, dual point Mallory, solid core plug wires, and no issues.

I'm not saying anything is wrong with using the later style systems. They work, more so when set-up right, all good components. Just choices.

Sorry to hear about the issues your having.

 

[Glenwood]

Yeah, I kinda suspected the coil, being at least part of the problem.

Don't take this wrong, thought about mentioning before, but when you gave the compression readings, personally think there's too much of a spread. All should be within 10% max. What can be done about that? Not much...maybe after time, the gap will close. Big reason your plugs are showing difference.


Yes on the charging issue, maybe check wiring too?
Choices on the ignition system, plenty of them. You probably already know what I have, pure old school...stock coil, dual point Mallory, solid core plug wires, and no issues.

I plan to rerun the compression tests at some point as I forgot to hold the throttle open during the test. Even so, none were over 5% difference. I want to inspect the valve train closely, once it is tucked away for the winter. I need something to do since I have nothing to weld this winter!

I'll pickup a VR today from Nigel up at national moparts. Hopefully it will be USA made instead of the china quality piece I picked up yesterday. I'll probably pick up another ECU too in case this one took a beating from the faulty VR. They also sell pertronix coils but I can't figure out if they need a BR or not. The pertronix website doesn't specify. Nothing wrong with old school, but I had my fill with points for both auto and marine years ago. I still prefer electronic.
I just can't figure out how I am reading such high voltage, but little current from the alternator though. Must be some sort of anomaly!

 

[miller]

I plan to rerun the compression tests at some point as I forgot to hold the throttle open during the test. Even so, none were over 5% difference.

I just glanced at your readings...thought a little more. (Sometimes I'm too quick, my fault!)
Yup, throttle needs to be blocked wide open. My tester has a release button, to reset the gauge, after testing. Pull all the plugs, pull the coil wire, then do the check. I was always told, for each cylinder, allow three hits on the gauge, to be accurate. If there's any chance the cylinder walls are dry...spray a little WD40 in each plug hole.

Ignition...fully agree...should use what your comfortable working with! I've used dual point distributors all my driving life.

Good luck on it.

 

[Ranger16]

I'll probably pick up another ECU too in case this one took a beating from the faulty VR.

I'm not sure which system you are using and I don't know how any of the others react to overcharging, but I can tell you from experience that the Mopar Performance ECU's do not like overcharging.

 

[Glenwood]

Working on a theory that there is a partially open circuit. What i mean is that if the wiring was starting to open at connection point, there might not be a charge at the battery when such a load is applied, but a sensitive digital meter may see the voltage at both sides of the faulty connection and the voltage may appear cumulative as if to place the alternator output in series with the battery as sort of a trickle effect. The old analog meters didn't have this problem.
Well didn't take long to find it. The new harness bulkhead wires are already melting! These had good clean connections and still are a source of problems. Should have rerouted the blasted wires when i put it back together. I'll do a temporary reroute and test.

 

[Glenwood]

yep, that was it! charging now at 13.8~14.4v. Current from the alt with low beams is 30A with about 21A going through to the headlight switch, gauges etc. and 9A to run the engine & charge the battery it seems. lights off and the alt drops to 16A with still 9A to run the engine & charge the battery. interesting (to me!)
I just crimped a large ring onto the black alt wire at the bulkhead and attached it to the starter relay post. Doesn't detour all of the current from the dash, but reroutes the battery portion away. If yearone ever replaces the tach I ordered in June, I'll remove the cluster to install it and then rewire these high current wires away from the bulkhead and may even reconnect the ammeter for fun!

Just to note, the old stock coil heats up to 150F even with the 1.6ohm BR in the circuit, but the secondary resistance stays below 12kohms, so the spark is probably borderline. A smaller resistor might help to bump up the voltage to the coil from 5.9V at 3A with the 1.4~1.9ohm primary coil, although it is running fine at operating temperature atm.

I have 18"hg of vacuum with a little fluctuation at about 17*btdc. Timing light is not working right so this 35+ year old light will likely be replaced unless I can find the cause. Turning the mixture screws 1/4 either way has no effect on vacuum so I'm not sure how to get it right. More reading ahead!

 

[Don Gould]

I have 18"hg of vacuum with a little fluctuation at about 17*btdc. Timing light is not working right so this 35+ year old light will likely be replaced unless I can find the cause. Turning the mixture screws 1/4 either way has no effect on vacuum so I'm not sure how to get it right. More reading ahead![/QUOTE]

Try pulling the vac line and bumping the timing to 30* at Idle, now check your vacuum and the carb should now respond to tuning adjustments. The amount of vacuum you generate at 30* of idle timing will tell us a lot about setting up the distributor. Also note your idle speed where you have it set now and how much RPM you get when you jack the timing up.

 

[Glenwood]

Thanks will do that.

 

[superfragl]

Lots of good advice here!
I will tell you what I did when I had similar situation with hot temperatures. Maybe that could help some.
I had a mild Lunati cam in my 440, 9.6:1 compression, Mallory 6A ignition module, Edelbrock 750 carb. On a hot day the coolant temperature would climb to 220 degrees and I was not really happy about it.
First thing that helped was setting initial ignition timing using vacuum gauge. It came to 20 degrees with 36 total (had to weld the slots), with vacuum advance hooked up it came to 52 total and the engine liked it.
Carburetor was adjusted to achieve highest vacuum at idle (15 inches).
The radiator was aluminum speed cooling 2-row. After adding a shroud I could feel the hot air flow from under engine compartment towards the back. That improved things a bit but still if the outside temp were over 100 degrees the engine would get to 205 - not bad, but I wanted better.
Next was smaller water pump pulley and high flow 180 thermostat - that did make a difference!!!
About a year later I put a gen III Hemi in my Fury and temperatures around 220-225 were usual (talk about running hot). I installed a Mopar severe duty II radiator with factory dual fans and that completely solved the issue. The radiator is one row 1 3/4" tube, which allows better airflow and better fin surface contact. It runs 194 degrees all day long now.

 

[Glenwood]

At 17* btdc, idles at approx 925rpm amd vac at 18"
At 30* idles increases by 100 rpm and vac still at 18".
No effect on vac or noticable change in rpm wth either ims turned 1/2 either direction. Smells rich though with both ims out approx 1.5 turns.
Btw, the mag pickup is about 890ohms and i gapped it to .008 as it was about .012.

 

[superfragl]

You have to stop advancing ignition when there is no much vacuum improvement anymore.
The throttle might be open too much. If you bring idle rpm down to 750 or even 700 by closing the throttle - does the mixture screw do anything now?

 

[Glenwood]

The vac max out at 18" around 25*. I dropped the idle to 700rpm and the vac gauge starts fluctuating a lot. Turning cw smoothes the needle out somewhat at 18". One ims is about 1.25 out and the other is about 1 turn out.