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914World.com _ 914World Garage _ Scary knock at 4k and above
Posted by: Headrage Jun 3 2005, 09:36 AM
I decided to drive my car to the office today since it really hasn't been out of the garage since the WCC and decided that since I've got over 500 miles on it I should be able to take it a little higher in the rpm range. As I'm leaving my daughters school on a long stretch of road I shift into 3rd and step on the gas pretty good. Car pulls really strong up through 4k then I get this rapid knocking sound. Got nervous, backed off and sounds gone.
I drove this thing all the way to Camarillo and back over the grapevine with absolutely zero issues and even took it over 4k during the failed poker run attempt.
Any thoughts???
Posted by: skline Jun 3 2005, 09:38 AM
Without hearing it myself, that is a tough one. I hope it is nothing serious. Although it does sound serious. 
Posted by: bondo Jun 3 2005, 09:52 AM
My MGB did that... perfectly quiet under approx 3500-4k. above that, rapid knock. It would go higher without knocking under low load conditions, but knock at a lower RPM at high load. Turned out to be a rod bearing.. I rebuilt it shortly after, and caught it before it spun... but it still looked ugly.
Posted by: skline Jun 3 2005, 09:54 AM
That is not what he wanted to hear. He just had that motor rebuilt.
Posted by: Dr. Roger Jun 3 2005, 09:58 AM
was the knock consistent with every turn of the crank (very fast knock), or perhaps more with the turning of the wheels (slower knock)???
Posted by: bondo Jun 3 2005, 09:59 AM
Well this engine had about a million miles. I just wanted to give him my knock experience, and explain the load thing. If it doesn't vary with load it probably isn't a rod. I of course hope it isn't a rod bearing, but if it is, the sooner it is figured out the better.
Posted by: Headrage Jun 3 2005, 10:00 AM
| QUOTE (skline @ Jun 3 2005, 08:54 AM) |
| That is not what he wanted to hear. He just had that motor rebuilt. |
I think that a rod knock would of been louder.
I hope.......................
Posted by: Headrage Jun 3 2005, 10:02 AM
| QUOTE (rogergrubb @ Jun 3 2005, 08:58 AM) |
| was the knock consistent with every turn of the crank (very fast knock), or perhaps more with the turning of the wheels (slower knock)??? |
It was a fast knock but I got off the gas as soon as I heard it and didnt hear it again the rest of the way to the office.
Posted by: bondo Jun 3 2005, 10:07 AM
Well my experience with valve noise is that it's most noticable at idle and gets drowned out by other engine noises at higher RPM. I have never heard a type 4 or any other aircooled engine rod knock, so I don't know how loud it should be. The MGB rod knock was a little louder than a bad ping, but lower in pitch.
One thing that could make a valve noise occur only at high RPM would be a failing valve spring... that's an awful hard thing to find without disassembly though.. unless it's real bad. With the right tools they can be changed with the head on the engine.
Posted by: Headrage Jun 3 2005, 10:23 AM
I was talking with my fleet mechanic and he says that a rod knock usually will not just go away. I should be able to hear it at all rpm's under load.
He's been wrong before though.....
Posted by: Dr. Roger Jun 3 2005, 01:34 PM
in my experience, rod knock is progressive but once it starts, goes bad quickly. and like your fleet mechanic said, it usually does not go away once started.
is there any chance it could have been ping???
like bondo said, the pitch is the tell-tale.
Posted by: SLITS Jun 3 2005, 01:51 PM
I got no clue.............
A rod is generally heard on acceleration whether it is under load or not. You should be able to rev the engine and hear it. When it's really bad where you can hear it all the time, you have about 5 seconds before the engine blows.
Was the day warm and did you have the shitty Bakertucky gas? It could possibly be detonation. You could try backing the timing off a couple of degees and go back out and see if you can blow it up.
I don't remember if you have any guages in the car. When a rod spins, generally the water temp goes up and the oil pressure goes down. 
Meaning, did the oil temp go up?
Posted by: Headrage Jun 3 2005, 02:20 PM
The car had only been running for about 10-15 minutes. Warmed it up in the driveway for about 5 minutes drive the 2 miles to my daughters school, idled while I unloaded her stuff out of the trunk and the maybe 1/4 mile down the road is when I got on the gas and heard it right above 4k. Temp gauge was only about 1/3 from the left. Not even fully warmed up.
Gas is Chevron mid-grade from Camarillo..................
Weather was 70 degrees and breezy.......................
Posted by: Aaron Cox Jun 3 2005, 03:25 PM
i had way too much advance once, and under a hard accell, i was detonationg.....
im with ron on this one. shitty gas and too much advance can do it....
describe the sound...
Posted by: redshift Jun 3 2005, 03:30 PM
I am with Rron, and GAayron on this one.
I had something I refuse to describe happen to me today.. ugly noise. 
M
Posted by: Headrage Jun 3 2005, 03:36 PM
So what's everybody doing this weekend. I'm thinking, drive down to Scott's house, fix problem, 
, back to Scott's house, 
, 
.
Posted by: Aaron Cox Jun 3 2005, 03:53 PM
| QUOTE (Headrage @ Jun 3 2005, 02:36 PM) |
| So what's everybody doing this weekend. I'm thinking, drive down to Scott's house, fix problem, , back to Scott's house, , . |
next weekend plz - i study for finals this weekend
Posted by: Headrage Jun 3 2005, 04:05 PM
| QUOTE (Aaron Cox @ Jun 3 2005, 02:53 PM) | ||
next weekend plz - i study for finals this weekend |
Gonna be in Mexico
Week after?
Posted by: SLITS Jun 3 2005, 04:08 PM
I have an engine for sale ::insert bite my tongue smiley:: 
Posted by: Headrage Jun 3 2005, 04:33 PM
| QUOTE (SLITS @ Jun 3 2005, 03:08 PM) |
| I have an engine for sale ::insert bite my tongue smiley:: |
Warranty?
Posted by: SLITS Jun 3 2005, 05:21 PM
| QUOTE (Headrage @ Jun 3 2005, 03:33 PM) | ||
Warranty? |
T.L.O.C..........taillights over the curb
Posted by: skline Jun 3 2005, 06:20 PM
You guys are baaaaddd! 
Posted by: Series9 Jun 3 2005, 06:34 PM
I think you should take it to an AX and see what happens....
Attached image(s)
Posted by: Headrage Jun 4 2005, 09:13 AM
I had a terrible thought last night. 
Could it possibly be pistons hitting something due to rod stretch???
Nah, that's crazy talk...... 
Posted by: Headrage Jun 4 2005, 05:59 PM
Maybe???
Posted by: SLITS Jun 4 2005, 07:37 PM
If your "rod" stretches that far.....I know somone that wants to meet you....................
Posted by: Headrage Jun 4 2005, 07:49 PM
That Darth is really good shit... I love ya Ron............
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