66 Dart Gt Idling issues/electrical

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MickeyKnox

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Good evening everyone. This is my first post. Anyone familiar with the 66 Dart GT 273 and had intermittent idling and backfires. It doesn't matter where the timing is set. So heres the backstory. Bought it. Not running. Heres the new items. Fuel tank, coil, plugs, Holley 4160 carb, blue streak cap and rotor, wires are coming tomorrow, she starts and runs now. But its weird. At idle let's say at 1K she idles down then up then backfires then up back down again. I'm getting enough fuel. Bought a new carb just to make sure. Checked fuel pressure. It's good. Could it just be a faulty distributor? Everything else is changed except for the Distributor, wires and ballast resistor. New wires and distributor coming tomorrow. Thanks for reading. And I'm glad to be part of the site. Edit I didn't change the PCV either.
20200509_200133.jpg
 
What are you using for ignition components, AKA is this a factory single point, aftermarket "whut?" and so on.

Start by checking for shaft play in the dist, look for dirt/ moisture / other in the dist. cap and rotor, and check overall general condition. Check all wires for continuity. "New" does not mean "good". Make CERTAIN all wires/ boots/ connectors and plugs are properly connected. Check the coil wire while you are at it

Check the spark cranking BY USING THE KEY. "Rig" a test gap using a solid core wire out of the coil. Should generate a nice hot blue spark about 3/8 or more typically 1/2" long

Check voltage getting to the coil. Should be at least 10.5 during cranking and "same as battery" during cranking. Running, should run (with engine running fast enough to keep battery at 14V) should be around 10-12V right at the coil
 
Also what is your feel for general engine condition? Have you run compression check/ leakdown? Any lifters making noise? Hows the oil look, IE clean, sludged up etc?
 
67Dart273 said:
What are you using for ignition components, AKA is this a factory single point, aftermarket "whut?" and so on.

Start by checking for shaft play in the dist, look for dirt/ moisture / other in the dist. cap and rotor, and check overall general condition. Check all wires for continuity. "New" does not mean "good". Make CERTAIN all wires/ boots/ connectors and plugs are properly connected. Check the coil wire while you are at it

Check the spark cranking BY USING THE KEY. "Rig" a test gap using a solid core wire out of the coil. Should generate a nice hot blue spark about 3/8 or more typically 1/2" long

Check voltage getting to the coil. Should be at least 10.5 during cranking and "same as battery" during cranking. Running, should run (with engine running fast enough to keep battery at 14V) should be around 10-12V right at the coil
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Ok. So does this sound more of an electrical problem rather than fuel delivery? I will find out tomorrow after the distributor and wires arrive. And run some tests. It just has me stumped. Oh and she runs identical with the old carb as she does with the new one. I'll look at the distributor in the morning and hit it with some electra clean. Ty for replying to my thread oh and aftermarket intake was already on when I bought it. Edelbrock performer 318/360 other than that all original
 
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67Dart273 said:
Also what is your feel for general engine condition? Have you run compression check/ leakdown? Any lifters making noise? Hows the oil look, IE clean, sludged up etc?
Click to expand...
Full fresh oil. And I can drive it. Once she hits about 2500 rpm to 3000 there isnt much of a problem. She wants to go. Drove it to work last week. And no. I forgot to get a pressure gauge today when I picked up the new carb. She sounds like panther at higher rpm with intermittent backfires here and there. I just cant get her to time consistently at idle. No matter where I set it.no top or bottom noises either
 
67Dart273 said:
What are you using for ignition components, AKA is this a factory single point, aftermarket "whut?" and so on.

Start by checking for shaft play in the dist, look for dirt/ moisture / other in the dist. cap and rotor, and check overall general condition. Check all wires for continuity. "New" does not mean "good". Make CERTAIN all wires/ boots/ connectors and plugs are properly connected. Check the coil wire while you are at it

Check the spark cranking BY USING THE KEY. "Rig" a test gap using a solid core wire out of the coil. Should generate a nice hot blue spark about 3/8 or more typically 1/2" long

Check voltage getting to the coil. Should be at least 10.5 during cranking and "same as battery" during cranking. Running, should run (with engine running fast enough to keep battery at 14V) should be around 10-12V right at the coil
Click to expand...
I am using all original components as much as I can. And I like that idea. I use the old put a plug in ground it and if you see a spark your good method ‍
 
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Explain the backfire a little more. Is it through the exhaust or out through the carb? Did this engine sit for a while not running? First suggestion after new ignition components, (cap, rotor, plugs, wires,) would be to run through the valve adjustment.
 
TT5.9mag said:
Explain the backfire a little more. Is it through the exhaust or out through the carb? Did this engine sit for a while not running? First suggestion after new ignition components, (cap, rotor, plugs, wires,) would be to run through the valve adjustment.
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Oh brother. I'm new to the internal workings of the motor. But I just self tought myself how to properly perform a compression test and wet test, after that a leakdown test. I will make a compression tester tomorrow. But for the leakdown I'll just connect with 30 psi. The backfire is exhaust btw.
 
What you really need is a timing light and a tachometer.
A 'distributor wrench' is handy but not neccessary - the hold down cap screw can be gotten to with sockets and extension or a box wrench with some creativity.

The initial timing of a 4 bbl '67 273 Plymouth is 10° BTDC at 600 rpm. Plus minus 2° is still within spec.
  1. Clean the timing marks.
  2. Connect the timing light's inductive pickup. - Place it over the #1 spark plug wire (front driver side) so the wire goes through the opening. -Route the wire so its clear of exhaust and the fan, belts, etc, and so you can hold the light pointing at the timing marks.
  3. Connect the tach/dwell meter if that's what you have for a tach.
Start the engine.
  1. If its not warmed up, get the engine warmed up.
  2. Kick it off fast idle. When it will run at slow idle (no choke), connect the timing light power. Most timing lights get power from the battery. Positve clamp to positive, the other one to negative.
  3. Remove the hose from the distributor's vacuum advance. Stick a golf tee in the hose. Alternatively, remove the distributor vacuum hose from the nipple on the carburator's side. Place a rubber cap over the nipple.
  4. Read the RPM and the Timing. Write them down
  5. Adjust the idle speed screw to change rpm and read the timing again. (write down how many 1/8 or 1/4 turns of the screw you make so you can go back if needed).
You should be able to measure and set the timing at 600 rpm.
If you can do that. Great!
If you want to check the mechanical advance is working, turn the idle speed screw in to bring the rpms up. Write down the new rpms and the new timing reading. Do this up to the top rpm of the tach/dwell - usually this is around 1200 rpm. If you have an dash tach and you want to measure at higher rpms, thats fine. When done measuring, return the idle speed screw to 600 rpm.

Reattach the distributor's vacuum hose to the vacuum port on the side of the carb.

Someone here may have the specs for '66 Dodge. It's probably the same or certainly close to '67 Plymouth non-CAP. But you should get your own '66 Dodge Service manual. Print editions are available used or reprint. Some free digitial editions are available for download. Go to mymopar.com and look in reference.
 
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Mattax said:
What you really need is a timing light and a tachometer.
A 'distributor wrench' is handy but not neccessary - the hold down cap screw can be gotten to with sockets and extension or a box wrench with some creativity.

The initial timing of a 4 bbl '67 273 Plymouth is 10° BTDC at 600 rpm. Plus minus 2° is still within spec.
  1. Clean the timing marks.
  2. Connect the timing light's inductive pickup. - Place it over the #1 spark plug wire (front driver side) so the wire goes through the opening. -Route the wire so its clear of exhaust and the fan, belts, etc, and so you can hold the light pointing at the timing marks.
  3. Connect the tach/dwell meter if that's what you have for a tach.
Start the engine.
  1. If its not warmed up, get the engine warmed up.
  2. Kick it off fast idle. When it will run at slow idle (no choke), connect the timing light power. Most timing lights get power from the battery. Positve clamp to positive, the other one to negative.
  3. Remove the hose from the distributor's vacuum advance. Stick a golf tee in the hose. Alternatively, remove the distributor vacuum hose from the nipple on the carburator's side. Place a rubber cap over the nipple.
  4. Read the RPM and the Timing. Write them down
  5. Adjust the idle speed screw to change rpm and read the timing again. (write down how many 1/8 or 1/4 turns of the screw you make so you can go back if needed).
You should be able to measure and set the timing at 600 rpm.
If you can do that. Great!
If you want to check the mechanical advance is working, turn the idle speed screw in to bring the rpms up. Write down the new rpms and the new timing reading. Do this up to the top rpm of the tach/dwell - usually this is around 1200 rpm. If you have an dash tach and you want to measure at higher rpms, thats fine. When done measuring, return the idle speed screw to 600 rpm.

Reattach the distributor's vacuum hose to the vacuum port on the side of the carb.

Someone here may have the specs for '66 Dodge. It's probably the same or certainly close to '67 Plymouth non-CAP. But you should get your own '66 Dodge Service manual. Print editions are available used or reprint. Some free digitial editions are available for download. Go to mymopar.com and look in reference.
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Yes. Its marked. I have set it at 10,13,15 pretty much with timing light. I'm actually agreeing with an earlier post in regards to valve adjustment. This beauty has been sitting a while. So I prefer to do warm adjustment with a feeler gauge. Which I cant find now. Lol of course when you need something. It's never around
 
Backfiring through the carburetor or the exhaust? Yes could very well be valve adjustment or valve timing (Timing chain and gears) But, let's not go there just yet.
I looks like a dandy.
 
Ok everyone. New distributor is in. Vac advance to old distributor was bad. She is idling smoothly now. #1 plug wire was bad looked inside distributor cap and identifying Mark's are all identical. #1 had none. Is there a chance that I could be one spark plug off from the left to the right or voice versus. Because when I put the timing light on at 10° it wants to stall and backfire but if I put it 20 -30 she idles fine. Does anyone have a pic on your distributor? I'm about ready to move all wires back by one. I would upload a video but it wont let me. And yes I pulled the vac advance off to time
 
Then it probably was already advancing.

A bad vacuum advance shouldn't have been involved when setting timing.
Also only causes minimal changes at idle when properly set up, even if the diaphram was bad.
Was it the original ? If so, dont exchange it - get it fixed.
 
MickeyKnox said:
20 -30 she idles fine
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Sure its in Neutral, there's no load, you can give it tons of advance and run it real lean since its only overcoming friction.
And as I stated in previous post, the timing is rpm dependent. 20* at 1200 rpm would be within spec for a '67 4 bbl 273.
 
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And one thing about setting the initial timing at idle rpm, (Usually 650 in drive for the automatics) it is slow enough to not effect the mechanical advance. And of course the vacuum advance hose is pulled and plugged.
 
6EE43E54-B82E-46B3-BC0C-B9D3EFB81152.jpeg
Here’s where my distributor is on my 273 charger engine with edelbrock and LD4B mopar electronic ignition.
 
Dartsun said:
View attachment 1715531626 Here’s where my distributor is on my 273 charger engine with edelbrock and LD4B mopar electronic ignition.
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Thanks. My #1 is facing directly to the front. Between 8 and 2 Your 1 and 8 are beside each other. If that makes sense heres a pic. Your front two are side by side my #1 is directly facing front ward. That's why I'm thinking I may be one plug off to the left and not getting correct timing. Or am I overthinking? My brains hurting the wires you see are for my trigger pull so I can do everything under the hood.
20200519_203846.jpg
 
I can get you a pic of where my number 1 on my distributor is pointing here in about 30m. Yours does look little to much in center.
 
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