General tune up parts for a 1970 455 with points

Want to get this all ordered this week to figure out why the Stage was running, very well, then dies flat on its face, not starting, backfiring (enough to blow out a muffler), once started, will not stay lit as it is given the smallest amount of throttle... I have both valve covers OFF, and all of the rockers and push rods are functioning...
The distributor has not been moved... Maybe I burnt out the points.. I just don't know...

 

There's only one condition that will blow a muffler off, Fuel build up from too much fuel!

Either a cylinder or more is not firing and that fuel then is going out the Exh, or the Carb is flooding out for multiple reasons and making for the same end result of fuel collecting in the muffler and then lighting off when there's enough heat to do so.

If the motor will start fine cold and hit on all cylinders ( depending on clean good plugs) then it's very likely not a spark or Distributor issue.

If you have a true duel Exh and only one muffler is blowing up then it's without question a Carb issue.

 

Yes- not the carb... Hence why I am focused on ignition parts.

Adam- they are all the same things it was on it when it left you.... I can assume it is all 10+ years old... Maybe 20!

 

To add to what Larry said - also use a points file. Burned/worn pints can have high spots. File the surfaces flat then reset.

 

I like the Standard ignition two part point condenser set I don't like the uniset and I always buy this in person so I can look at the contacts and see how they meet before buying.

Also I would run a timing light across all 8 and make sure all are firing. a miss would be dumping unburned fuel on the exhaust cycle.

 

NO! NO, no, no, absolutely NO.

Actual GM spec is to not dick with the "high spot" until it's larger than the gap. The cone of transferred metal on one "point" matches a conical divot in the other "point", the transferred metal becomes additional surface area leading to better contact/lower resistance.

For the record, if you look at the cone of transferred metal, it'll tell you if your condenser/capacitor in the distributor has too high or too low of a value. You look to see if the cone is on the stationary contact, or on the movable contact, and that tells you if the condenser is too "big" or too "little". Then you measure twenty condensers with accurate equipment and compare to the existing condenser to find one that happens to be closer to optimal. I haven't wasted my time on contact-controlled ("points") ignition in over thirty years (God bless HEI!) so I don't remember which way means too "big" and which way means too "little", although someone reminded me about three years ago.

That cone of transferred metal is also why checking "gap" on used points is "pointless", use a dwellmeter instead.

Quality points sets have Tungsten plating on the contact surfaces...tungsten has a very high melting point, which is why some arc-welding (TIG/"Heliarc") is done with Tungsten electrodes. You put a file to those tungsten-plated points, and you destroy the tungsten plating, which leads to even faster deterioration of the points set.

"Points files" are great for removing the ragged end of your fingernails. Keep them the hell away from your ignition points.

 

Sounds like the condenser is bad...

 

OK - I am assuming the points are shot any way and the cone has grown to where the gap is gone. Using a file will knock the cone down and open the points( see Larry's thread above) to see if the car will run. If the car will not start there is another problem too. Follow Larry's post. The file is not a normal maintenance process, as you "pointed" out!

 

The cone of transferred material does not "close" the gap. What transfers to one contact creates a matching divot on the other contact. There's still a gap. Check with a dwellmeter, not a feeler blade.

You could close the points, and check resistance through them. High resistance will prevent the coil from properly charging. Low resistance (nearly zero) means the coil should still charge.

If the condenser fails, the engine can be non-starting or hard-starting but it might run (poorly) if you get the rpm up. The condenser not only creates a sudden drop in coil amperage which creates the spark, it also minimizes the metal transfer from one contact to the other. The faster the metal transfers from one contact to the other, the farther away from the optimal value the condenser is.

They say that half of all "carburetor" (fueling) problems are in the distributor. It's also true that plenty of "distributor" (ignition) problems are caused by the fuel system. If the car is hard-starting, then stalls when the throttle is opened, ignition is not the only possible cause. Verify choke, fuel pressure, float-bowl level, accelerator pump-shot, etc.

 

I got all new ignition parts… going in tomorrow

 

Thanks Larry! Called Larry on the phone…. “Try jumping the coil from the battery”….. fired right up and idled….…. Some small misfires…

thanks Larry and Adam!