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318 Horrible Noise

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will c

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"Alright so I took my boat out

"Alright so I took my boat out today like normal and cruised for 10-15 minutes @2500-2800rpms with no problems. then I stoped and fished for about an hour, after that I decided to go somewhere else so I started it up and tried to get on plane but I heard this horrible racket once above 2400RPMS. So I limpd home at around 2000RPMS and it would not make any noise at that speed.

it had around 45 pounds of oil pressure. Then when I revved it in neutral it went to 60 easy when warm. I had to rev to almost 4 grand in neutral to make it make the noise.

It sounds loud but not as loud as rods. What does detonation sound like?

thanks for any help and sorry for the long post will
p.s. If anyone is interested I may be able to take an audio and video clip."
 
"I also just filled the tank u

"I also just filled the tank up with 87 octane instead of the regular 91 would that matter.
engine has about 400hrs and the heads have about 2 on a fresh valve job.

thanks again, will"
 
I hope its not a blown head ga

I hope its not a blown head gasket. My 360 sounded like that.

I suggest getting a compression test run BEFORE running it any further. You don't want to fire etch and wreck the block.

Jeff
 
"Couple Questions, What is fir

"Couple Questions, What is fire etching? It Idles super smooth but I will do a comp check today.
thanks, will"
 
"So I did a comp check all wer

"So I did a comp check all were between 125-135. I ran it some more on my trailer and the poping/clacking seems to be coming from the carb when I put my head to the oil pan the noise gets quieter it is loudest when my head is above the carb . I can make the noise now just by goosing the throttle.
Oil is clean with 2 hours on it I am going to check the timing.

thanks, will"
 
I think I have a flattened cam

I think I have a flattened camshaft one of the rockers barely moves while running compared to the others.

will
 
"That'll do it. "Fire

"That'll do it. "Fire etching" is where the gases escaping thru a blown head gasket cut a groove in the block and heads, wrecking both. Thank heavens that's not your problem. A cam change is easy on that motor, and fairly cheap. Be sure to change out ALL the lifters as well.

jeff"
 
"Yeah I am picking up the cam

"Yeah I am picking up the cam and lifter set today I will start tommorow after work, hopefully break the cam in on Friday and then be on the water on Saturday.
Now that you mention it I have seen those grooves coming out of the combustion chamber the a set of heads I took off of a 351W I didnt know what it was!!
thanks jeff, will"
 
"..." I didnt know what it

"..." I didnt know what it was"

It's money coming out of one's wallet! I had that happen to one of my engines and, through ignorance, ran it until it was junk.

Jeff"
 
I'm thinking bad valve sea

I'm thinking bad valve seat. Maybe came loose and is holding the valve open

Justa thought. I had it happen a few years back

Dean
 
THe seats in that motor can&#3

THe seats in that motor can't "come loose". THey are part of the head. One piece.

Jeff
 
"These heads did have hardened

"These heads did have hardened exhaust valve seats installed during the valve job. But I did a leak down test on that cylinder with rockers off and it checked good. I pulled the cam and lifters and the lobe of the cam is bad along with the corresponding lifter.
I am reassembling the engine today I will keep you all posted.

thanks, will"
 
"Well I finished it up today a

"Well I finished it up today and broke in the cam. It is running great no funny noises at all. I will test it on the water this Thursday,

thanks for the help, will"
 
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