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popping through exhaust

gunkholer

Member
I have a pair of 454 crusader engineswith Edelbrock carbs 1410. My stbd engine recently just started torandomly pop through the exhaust. I haven't taken it out and put itunder load yet, but at the dock I've revved it up to about 2200 rpm. I've checked simple things like loose plugs or plug wires and anyloose wires or corroded wires.
I checked previous threads on this topic but I didn't really see anything that might give me a clue.
There are two circumstances that mayhave caused this or perhaps they are both coincidental.


I think I might have run out of fuelprior to this happening. I know I was getting low and the fuel gaugewas showing about 1/8. When I fired up the stbd engine one day itfired up fine but the rev's wouldn't increase when I moved thethrottle lever. I shut it down and added about 70 litres of 91octane. It still did the same thing when I fired it up again. Iremoved the fuel filter that's on the engine. It's close to thesolenoid. It was about 1/2 full of gas ( no dirt) and I added a bitmore, reinstalled it and then I fired up the engine again. I hadjust recently replaced that filter canister as well as the largerfuel filter canister on the bulkhead. Both filters have about 2hours run time on them. At that point I assumed it might be an airlock perhaps. But then the popping started again when I fired it uponce more. So now I'm thinking perhaps there was some settlement inthe bottom of the float bowl that was sucked up. I'm wondering if Ishould try some SeaFoam?

The second possibility was that justprior to the rpm not increasing, I tried using my new fresh waterflushing out system that I recently installed for the first time. Prior to starting the engine I closed off the raw water ball valveand turned on the fresh water ball valve and fired up the engine. Itran for maybe one to two minutes before I realized the fresh watertank had drained due to a loose hose clamp. Yes it was dumb not todouble check that there was water in the designated fresh water tank. I installed a clear poly tube vertically on the side of the tank,but it's difficult to see and I mistook it to be full of water whenit was not. However there was still some water in the 1 1/4 in.line running from the tank to the raw water pump. So the raw waterpump may have been starved for a short while. I haven't pulled thepump to check the impeller yet. I reversed the ball valves back sothe engine is fed with raw water again. I don't see how this mightcause popping but it's the only other variable that changed since theengine was running fine last week.
 
If it ran lean, you could have burnt a valve...compression test will give you and indication, a leakdown test will tell for sure....

The other thing that comes to mind is the distributor advance could be frozen (rusted)....checking the timing will tell....
 
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