Hey everyone, my dad has a 455 in his 1970 delta 88 and every so often as we let the car warm up before we take to wherever we go, it suddenly dies and then becomes very difficult to start again. Any ideas?

 

It most likey would be fuel or ignition related. Time to start diagnosing.
Has it had a tuneup done recently? Fuel filter, plugs, and all that stuff?
Carb rebuilt in the last 10 years? How's the vacuum hoses look? Timing okay?
How does it run when it finally restarts?

Does it shudder, buck, or lose power before dying or is it like turning the key off?
I had the latter issue on my old Ford. The electronic pickup in the disty was bad (not one in your car if it is stock) but a bad coil could do that for sure.

When it dies, pull the air cleaner, look into the carb and open the throttle. Look for a couple squirts of fuel, one in each of the primary barrels. If you see them, then it might not be fuel related. However, it could be a vacuum leak though if it runs rough before dying.

 

I'm going to suggest a "heavy" float in the carb. The plastic float materials used in the 1960s-70s are attacked by the additives in today's gasoline and can absorb fuel, becoming less buoyant. The result is a higher than expected fuel level in the float bowl and resulting flooding. If the problem is minor, the engine will run fine when cold or at elevated RPMs, but will flood out and die during warm idle. When was the last time the carb was rebuilt, and was the float replaced at that time? These days I replace the float at each carb rebuild, or get a brass float instead of the original plastic.

 

Wow, never knew that about the floats. I just rebuilt the carburetor (2 brrl rochester) recently, without replacing the float. The guy at my local shop i took it to said it was fine. It has had a tune up but i think cap and rotor haven't been replaced.

 

What about something electrical shorting out after getting warm enough? Coil or condenser? If it was the float, the plugs would be black, no?
Read the plugs.
What do you think, Joe?

 

It could also be the fuel pump. Take the fuel inlet off and check the flow to the carburetor.

 

Reading just 2 or 3 plugs would send you in the right direction. Fuel or ignition. Find out which direction to go FIRST, and then dig in that direction.