Ford 460 Does Not Start Only Backfires When Cranking Over

Question

I have a Pioneer Jet Boat with a Berkeley Pump attached to a Ford 460 big block.

The 460 has a Holley carbureter, and Basset water-injected headers.

The engine was running fine until one day when pulling the boat out of the water and putting it on the trailer, we went to try to start it to drain out any excess water and it wouldn't start. We attributed it to being out of fuel. We gassed the boat back up and hauled it back home not thinking anything of it.

The next day we try starting it and aren't having any luck. Whenever the motor is cranked over it doesn't even try to start and we only get backfire out of the carb or pipes.

We've compression tested it, did a carb rebuild, replaced the plugs, and put a new fuel filter in it without any luck.

We know it's getting fuel because the fuel filter fills up and we see fuel spray into the carb when the throttle is depressed.

We know it's getting spark because we've pulled every plug and tested each plug individual for spark by plugging them into their wires and holding them to the motor (for ground) and watching them spark.

We know it's getting fuel because, well, there's nothing on top of the carb, just open while we work on it and covered up when we're not.

We've also triple checked the timing and we're 99% sure it's ok. Any ideas or input would be of immense help.

Answer 1

After compression checking and pulling off the valve covers it was obvious there was no traumatic damage. Rebuilding the carb helped (because after we solved it we had a huge surge in horsepower) but didn't solve the problem. It was only after we had called a local machine shop and described the problem just like above where they had mentioned "are the gears on the distributor shredded?". It was that vouala moment where we had realized that we weren't checking the distributor close enough and that there was a problem with it. The gear that was driven by the camshaft had been forced loose and caused the pin that secured it to be sheared. It was only after replacing that pin and repairing that gear where the distributor was being driven that we were able to pinpoint the cause of the problem. It was timing all along. But timing as a result of a stripped gear.

The gear itself is steel and the machinist mentioned that if it had been bronze that the gear would have been sheared for safety reasons forcing us to change the oil if so (all that bronze would have made it's way to the oil pan and through all the oil galleys). Our gear however was steel and had not been destroyed, only the pin which held the gear in place.

We are back on the water and very pleased with all the extra work we did to the carb ;)