Reply With QuoteIt sounds like the engine may have leaned out.Was it starving for fuel?Are there any vaccume leaks?
The boat was running a little funny so we pulled it out and brought it up the house.
Its a blown 671 468 alum heads solid roller cam, msd , very low boost 3lbs and the noise i was hearing was coming from a cracked header. The boats a flatbottom v-drive
BUT>>>>>when the header was removed it was clear that one of the cylinders was silver with zero carbon or black residue, the rest were blackish like typical. I got a flashlight and placed it in each exhaust port and it almost looks as if the tops of the pistons are deteriorating away (JE's). The one cylinder that caught my eye though was almost completly silver dust.
What could cause this?? We were running 110 octane at I believe 32 degress timing?
It sounds like the engine may have leaned out.Was it starving for fuel?Are there any vaccume leaks?
It's possible that the cracked header could have caused a lean condition in that cylinder. I had a small exhaust leak on a motorcycle , it got so hot one night, that a friend stopped me because the header was GLOWING red hot. I can only imagine the heat from a blown engine in that cylinder.
Darrell.
Its more likly that a lean condtion cuased the cracked header.
Could too low of fuel pressure have caused this? 5psi I believe. What should be the first step before putting it back on the water. Im just scared of granading the thing
Your fuel pressure should maintain 7 psi.Running out fuel is a lean condition.You can perform a leak down test.This will show what got damaged.If you burnt pistons they need to be replaced.Pull the heads off for further inspection.You said eariler that the pistons look to be deteriorating.Excessive detonation will leave pit marks on piston tops and possibly burn down into the top ring land.You need to check valve job also.With that much cylinder temp you can cup the valves.With the leak down test you should be able to find this.
Can't say for certain......
Usually a clean piston, chamber and exhaust port means a coolant leak into that cylinder (in a boats case.....water). The water in the cyl cleans up all carbon. Now it could be that when the boat is put away that the water in the block drains down into the cyl and sits on the piston for awhile....leading to a deterioration of the aluminum....which may be the "dust" that you see.
Possible head gasket problems? Just some thoughts.
Curious, What cylinder was it?
You should check your plugs for aluminum deposits, ie- piston material it will transfer to the plugs during detonation. The silver (or white?) you see and the piston deterioration is either a lean condition, too much timing or caused in that one cylinder by the header leak. Check to see if the timing has slipped, run the coolest plug possible, and listen for detonation under w.o.t. Your fuel psi a 5 pds is a little low but should be alright. can you run a higher volume pump? Carter makes a good high volume mechanical that requires no regulator and keeps up with my blown 498 with dual 750's. Let us know what's happened, I'm curious.
You should check your plugs for aluminum deposits, ie- piston material it will transfer to the plugs during detonation. The silver (or white?) you see and the piston deterioration is either a lean condition, too much timing or caused in that one cylinder by the header leak. Check to see if the timing has slipped, run the coolest plug possible, and listen for detonation under w.o.t. Your fuel psi a 5 pds is a little low but should be alright. can you run a higher volume pump? Carter makes a good high volume mechanical that requires no regulator and keeps up with my blown 498 with dual 750's. Let us know what's happened, I'm curious.
Right on the money.
Be good, Jim
I just got off the phone with my dad and here is the latest,
Pulled the blower off and pulled the heads and to his surprise the cylinders and pistons were flawless!! It looked as if there was deterioration of the tops when shining a light into the exhuast port but i was wrong!
One plug was cracked and not firing, the rest looked cocoa brown maybe a tad bit darker. Performed a leak down test and the cylinders would not even hold 50 psi, and there was a leak. Sounded like it was coming from the exhaust valves he said, but he was unsure. When he took the head off the valves looked fine, and would seal, placed a liquid in it and no drips. So the next thing we were thinking may be head gasket??
Next step is to get new head gaskets and retorque, had the cosmetic gaskets to 75lbs. To loose???
Im just glad everything is looking good so far, any suggestions
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