theesir

Hi all,
I do my best to do-it-myself whenever possible, and have hit one of those "I don't know where to start" moments.
Up until a week ago, my 69 (350) has been running GREAT, smooth idle, excellent acceleration, the works.
About a week ago I noticed a bit of vibration, which I now attribute to the motor running a bit rough. Yesterday, with a warm engine, I got a loud backfire (in the carb-- all backfires I hear are in the engine compartment) when I started the car and the engine stalled. I was able to start but then the ride was terrible. Occasional backfire on first gear acceleration and definite loss of power. On acceleration in 4th gear, I get a hesitation and then it begins to go. Today on cold engine start, it backfired and stalled (but did start).
Now here's where my limited knowledge comes into play. I believe the issue is in the ignition system (plugs--->distributor (regular points distributor by the way).
I don't know where to start trying to track this down.
Do I start by pulling and inspecting the plugs, replace distributor parts, check timing? All these things may be playing a roll (I think), I just don't know if there is some testing I could do that would help me narrow down the problem.

Thanks

Duke94

Check the points first, then pull plugs. Make sure a plug wire didn't come off.

Gary

theesir

A bit of an update and then a question. I started the car and then one at a time pulled and replaced the spark plug wires from the distributor.
The 2, 3 and 5 cylinders do not seem to have any affect. They show spark from the distributor, but the cylinder does not seem to be firing as there is no additional "roughness" in the idle when those are pulled. Each of the other wires when removed cause a rougher idle.
I then pulled 2, 3 and 5 all at once and again, no effect on idle and when each were put back on one at a time no effect.
Wires seem solid I have checked each, no arching and no worn/melted shots. I tried switching wire from cylinders that worked to those that didn't and same 2,3,5 seeming failure exists.

Could this still be the points? If so how do I check them. If not, is replacing the spark plugs the next step.

Duke94

Pull the plugs next. Do you know when the cap, points and plugs were repalced? If you don't know the history, replace the plugs when you pull them. Cheap insurance.

Gary

theesir

the points have not been replaced since I have owned the car (6 years or so). I pulled a plug from one of the "non-working" cylinders and turned the car. The plug was definitely showing spark.
I will replace all the plugs. Could the points be affecting the cylinders not all seeming to fire?

mds3013

Bad plugs can fire when not in their holes and under compression. mike...

Duke94

Check the dizzy cap and make sure all the terminals (the part inside the cap) are not burned. I would say if the points were shot it would affect all cylinders. If nothing has been replaced for over 6 years, I'd say you are ready for a tuneup. Points, plugs, cap etc.

Gary

theesir

Everything inside the cap looked clean. No carbon. It has been six years, but if I have put 700 miles in that time it is a lot. I am going to replace all pieces and see what the effect is.
Thanks, I will report back after all has been done.

...Roger...

If you have a temp gun shoot the exhaust manifold to try and find a cylinder thats cooler than the rest. Then pull the valve cover and see if you flipped a rocker.

my 76 ray

Pull the valve covers and make sure the valves are opening on the dead cylinders. If an exhaust valve isn't opening the result is a backfire when the intake valve opens.

markdtn

If you have a Holley carb and you have a backfire you will have blown the power valve inside. Just a thought.

TeaEye

How can you check the valve to see if blown?

TeaEye

Here is video on how to check the Power Valve. After the explanation of the valve, the video tells how to check it.

http://www.youtube.com/watch?v=6vKlA...eature=related

1972corvette454

I had the exact same problem, check the condensor (next to your points)
I replaced mine and problem solved

MotorHead

Check to see which vacuum line got disconnected

Mr.Gearhead

A few years ago I had the same symptoms. Rough idle, lag on WOT and backfiring through the Holley. Mine was breaking up at about 4-5 rpm too..

for me... it wasn't the ignition or those related components. I believe some of the other forum members are on to something if the ignition checks out. The valve train... rocker... or in my case a munched lifter. I had an exhaust lifter wipe out and took a cam lobe with it. If all else fails you can remove valve covers and watch the rocker movement. Mine was very easy to see as the exhaust cam lobe was completely gone.

Hope this helps and good luck.

theesir

OK, so in the interest of starting with the simplest solution first, I have purchased plugs, cap, rotor, points and condenser.
Under the rotor, on the distributor there are 2 balance weights(?) that have springs attached to them. The points and condenser are underneath that. Do I need to remove that before I remove the points? If so, how do I unattach that unit.
Thanks

theesir

Ok so I embarked on replacing the plugs, cap, rotor, points and condenser

Replaced plugs, cap and rotor, started the car and it continued to run rough.
Replaced the condenser and points, checked the initial gap an assured it was at .019, replaced the rotor and cap- tried to start and NO spark at all.
Put original points and condenser back, still no spark.

What could I have done. I have checked and it does not seem that I have disconnected any wires or hoses.

Where do I start in trying to find my missing spark!

my 76 ray

Did you have the rubbing block on the points on a high point of the distributor shaft when you set the gap?

Do you have the condenser wire or power wire to the points grounded out on the body of the distributor?

theesir

I did test the gap on the high (point of the lobe) of the shaft.

Should I be grounded or not? Here is a picture.
Is there anything obvious I have wrong???