calebad

Okay, so here's the story: I decided to upgrade the power valve on my holley carb to an 85 from a 65. It ran very rough, almost like it was misfiring, the timing was very bad, or it wasn't firing on all 8 cylinders. It would stall if I let it idle at all, and had a very hard time accelerating when I tried driving it a short distance. So naturally, I swapped the old 65 back in. Now it won't start at all. It used to run a little rough like that when I started it on cold days, but only for about 30 seconds. Is it possible that it is some other issue that coincidentally got worse right now?

My info is probably way out of date so here's what I have that may help:
350 with a holley ultra street avenger VS carb, MSD distributor, cap, and wires, mild cam (came in the engine when I bought it so I don't know the specs)

calebad

Update:

I fully cleaned the primary side with seafoam and blew all of the passages out with compressed air to ensure that there was nothing blocking fuel flow. I noticed that the primaries had a little soot buildup, as if there might've been a backfire. That still shouldn't stop me from starting my car though.

After trying that, she still wouldn't start, so I pulled the plugs, saw that they had a lot of carbon buildup, and so I replaced them. Still wouldn't start.

Next, I checked the coil with a meter to check to see if it was any good, sure enough its impedance was far too high (9ohms on the primary when kt should've been 0.3) so I replaced it, but it still won't start.

It's possible that I did fix it by replacing the coil, but my battery was running very low from trying to start it so many times. Tomorrow I will boost it and find out for sure.

calebad

I tried boosting it today, but it still wouldn't start. I pulled the rotor off the distributor, and it looked nice and clean underneath. I even yanked the whole distributor off to look for damage or grinding with the camshaft, but there was nothing wrong there.

I have no idea what's wrong. There is plenty of fuel going to the engine, I even flooded it once. (No, I'm not stupid, I pulled out the plugs for an hour to dry out the cylinders afterwards)

Once while my friend was cranking the engine over I heard a grinding sounds, and the engine shook. He turned off the ignition right away. It sounded to me like the grinding came from the back of the engine.

Can anybody help me out here?

Ingram78

Still running a vacuum advance?
Is it getting fire?

calebad

Yes, I'm still running vacuum advance.

I yanked a plug to check for an actual spark (there was none before I changed the coil) and she fired right up. Go figure. For some reason it didn't want to run after I changed the coil, but a few days later it did. I guess that this will go down as another problem that I have solved without knowing how.