Diagnosing Exhaust Sound

[toolmanmike]

Also, I have an electric choke, and the hot side is only getting 8.9 volts??

Is it hooked to the ballast resistor? The wrong side of the ballast resistor?

 

[1967coronet]

Chokes not a big deal right now as long as it opens . You need to check voltage at the driver side of the ballast resistor. Most pull choke power from that.
Did you drain the 5yr old fuel out of the tank?
If it was ethanol blend its dbl trouble.
Myself I prefer the non ethanol fuel.
If you eddy 750 sat for 5 yrs it needs soaked & rebuilt.
Your voltage is correct for your coil and distributor.
That backfire is prob crap fuel ( you can't blend out crap fuel ) carb needing rebuilt , and as mentioned wires / fire order or a combo.
I'm kind of suspecting the carb / fuel after hearing of the 5 yrs storage.

 

[Dan The Man]

Chokes not a big deal right now as long as it opens . You need to check voltage at the driver side of the ballast resistor. Most pull choke power from that.
Did you drain the 5yr old fuel out of the tank?
If it was ethanol blend its dbl trouble.
Myself I prefer the non ethanol fuel.
If you eddy 750 sat for 5 yrs it needs soaked & rebuilt.
Your voltage is correct for your coil and distributor.
That backfire is prob crap fuel ( you can't blend out crap fuel ) carb needing rebuilt , and as mentioned wires / fire order or a combo.
I'm kind of suspecting the carb / fuel after hearing of the 5 yrs storage.

Carb rebuilt, new fuel pump. Tank was drained and a few gallons of Rec 90 added. The hot side is running through the fire wall, but have not traced it yet.

 

[1967coronet]

Carb rebuilt, new fuel pump. Tank was drained and a few gallons of Rec 90 added. The hot side is running through the fire wall, but have not traced it yet.

When you say REC 90 do you mean regular 90 ? if so that should be fine.
stock oem style fuel pump ? or higher pressure electric or mechanical ? the carter / edelbrocks only work right at 6lbs fuel pressure or a hair under.
Try a spare ignition box if you have one.
Glad you drained the tank, one thing to ck. of the list. Did you rebuild the carb ? if not pull the top plate and check it out. See if its full of crud , floats adjusted at 5/16 top of float to plate when closed & 13/16 hang off plate when open.
I know its been done lol. but get #1 up to tdc pull the cap make sure your rotor is pointing at #1 terminal and check the wires.

We all have had to fight this stuff before, Im not above trying a known good carb from a friend or distributor to narrow things down.
bump the timing up to 15 advance.

 

[Skytrooper]

I had a similar problem with mine. I couldnt figure it out until Don Frelier. came over. He double checked everything I had done. Then he discovered that 4 out of 8 plugs were not firing....and they were brand new ! I changed them out and it runs great.

 

[Dan The Man]

When you say REC 90 do you mean regular 90 ? if so that should be fine.
stock oem style fuel pump ? or higher pressure electric or mechanical ? the carter / edelbrocks only work right at 6lbs fuel pressure or a hair under.
Try a spare ignition box if you have one.
Glad you drained the tank, one thing to ck. of the list. Did you rebuild the carb ? if not pull the top plate and check it out. See if its full of crud , floats adjusted at 5/16 top of float to plate when closed & 13/16 hang off plate when open.
I know its been done lol. but get #1 up to tdc pull the cap make sure your rotor is pointing at #1 terminal and check the wires.

We all have had to fight this stuff before, Im not above trying a known good carb from a friend or distributor to narrow things down.
bump the timing up to 15 advance.

"Recreational fuel" non ethanol 90 octane. I have a feeling its the fuel. Carter 6903 (6-7psi). I have a spare box and coil. Carb was rebuilt. I'll bump up the timing to 15. The frustrating thing is this car ran like a champ before sitting. Can't see why all these things must be checked out...but I'll go through the motions.

 

[Dan The Man]

I had a similar problem with mine. I couldnt figure it out until Don Frelier. came over. He double checked everything I had done. Then he discovered that 4 out of 8 plugs were not firing....and they were brand new ! I changed them out and it runs great.

Unreal. I just changed all 8. I need to pull the wires one at a time to make sure they are all firing.

 

[Dan The Man]

Honestly, since this car sat, the ONLY thing I did of any significance was rebuilding the carb. and change out the fuel pump.

 

[khryslerkid]

Unreal. I just changed all 8. I need to pull the wires one at a time to make sure they are all firing.

That's what I was going to suggest. It will show a bad plug, wire or cylinder. (Bent pushrod)

 

[Slap Stick]

"Recreational fuel" non ethanol 90 octane. I have a feeling its the fuel. Carter 6903 (6-7psi). I have a spare box and coil. Carb was rebuilt. I'll bump up the timing to 15. The frustrating thing is this car ran like a champ before sitting. Can't see why all these things must be checked out...but I'll go through the motions.

Why do you think it's the fuel? It's all fresh stuff.

 

[Dan The Man]

Why do you think it's the fuel? It's all fresh stuff.

Because everything else is checking out ok. I tested the ballast, coil and pu coil. Cap, rotor, wires and plugs all good. Final test is pulling the wires one at a time. Plus I've never used this fuel before and maybe its not meant to be used in these BB. I bought a can of 110 leaded gas. Stay tuned

 

[Slap Stick]

You dont need all that octane. In fact that might make it run worse.
You said it ran okay before you rebuilt the carb.
I would be looking at that.
The fuel you have should be okay unless it is contaminated.

 

[Dan The Man]

You dont need all that octane. In fact that might make it run worse.
You said it ran okay before you rebuilt the carb.
I would be looking at that.
The fuel you have should be okay unless it is contaminated.

Run worse? How so?

 

[1967coronet]

Run worse? How so?

Another member with a problem kind of like yours on another thread.
He was looking at the fuel system also , car had sat for a few years. ended up being a bad coil.

 

[moparedtn]

If that video is any indication, that rascal isn't hitting on all 8.
That isn't likely to be a fuel thing.

 

[Dan The Man]

If that video is any indication, that rascal isn't hitting on all 8.
That isn't likely to be a fuel thing.

Well all that is left ignition wise is to swap out the ECU with a known good one and pull each plug wire one by one. Coil, pu, cap, rotor, ballast, plugs and wires are all good to go.

 

[Dan The Man]

If that video is any indication, that rascal isn't hitting on all 8.
That isn't likely to be a fuel thing.

It's firing on all 8. Used the timing light on every wire and got a very strong strobe on all. The weird thing is I put both my hands over the carb while idling and it just about sucked the skin off my hands. But only that one time. Then no reaction after that. I still have a crappy throttle response from stop, but I believe that is the gas cable/linkage adjustment. I do have some exhaust leak going on around the heat riser/passenger side exhaust manifold. HEED THIS WARNING! NEVER LET YOUR CAR SIT IDLE FOR LONG PERIODS OF TIME! My a** hurts from kicking myself.

 

[moparedtn]

Does it sound any different than in that video you posted at this point?

 

[Dan The Man]

Does it sound any different than in that video you posted at this point?

It does seem less, but maybe I'm use to hearing it at this point.

 

[moparedtn]

It does seem less, but maybe I'm use to hearing it at this point.

There's a really odd burble to the exhaust note for a 440 for sure....if it isn't ignition, well....
I'll leave it to the more knowledgeable engine guys here,
Maybe it's time for a fresh video?