Spark Knock, Death Knock, valve train knock????? - Off-Road Forums & Discussion Groups
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post #1 of (permalink) Old 09-15-2003, 07:33 PM Thread Starter
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Spark Knock, Death Knock, valve train knock?????

I have fenderwell headers and glass packs, so it's hard to hear it.
It doesn't knock at idle at all.
It knocks from say about 2000RMP up.
It needs to have a little load to knock, so just revving it in the drive way wont help me find it. But it doesn't need much at all.
If I'm wound out in 2nd and let off a little I can hear it, but if I let off enough that I don't have any load it stops.
It wont knock under load at low RPM's

How do I diagnose this?????

I just got the Q-Jet running good when this started. Could it be a vac advance issue?
I'm thinking about hooking up the E/brock and seeing if it goes away.
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post #2 of (permalink) Old 09-15-2003, 09:55 PM
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Re: Spark Knock, Death Knock, valve train knock?????

probabaly what you have is called detonation. cause is low octane fuel normally. you can corresct the issue by running beter gas or retarding your timing (retarding your timing will cause serious power loss).
If this isn't you have an engine running hot.
post #3 of (permalink) Old 09-16-2003, 02:37 AM
 
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Re: Spark Knock, Death Knock, valve train knock?????

Pull your plugs, take a look at them. If they're burnt/cracked/blistered your timing could be way off... or you could be running really lean, which would cause you to also run way too hot... which would cause detonation, among other things.
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post #4 of (permalink) Old 09-16-2003, 09:25 AM
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Re: Spark Knock, Death Knock, valve train knock?????

You *REALLY* need to GO BACK TO WORK!!!

...before you find anything else wrong with your trash!
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post #5 of (permalink) Old 09-16-2003, 09:42 AM
 
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Re: Spark Knock, Death Knock, valve train knock?????

To see if it is ignition timing related, measure your present timing, then retard the timing a couple of degrees at a time and do a test run. If less advance cures the problem, then you are done.

It could also be something simply making noise, like a leaking exhaust or some part rattling.

I don't think it's valvetrain, as it would rattle whether there was load or not.
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post #6 of (permalink) Old 09-17-2003, 01:27 PM Thread Starter
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Re: Spark Knock, Death Knock, valve train knock?????

I changed the carb back to the E/brock.- no different
I retarded the timing.- no different
It started to get worse and then started to backfire with even the least bit of deceleration. Now I'm thinking it's a vacuum leak at the intake.

Anyone care to comment?
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post #7 of (permalink) Old 09-17-2003, 01:47 PM
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Re: Spark Knock, Death Knock, valve train knock?????

how are your rpms at idle? do they fluctuate, are the high? have you checked your spark plugs yet?

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post #8 of (permalink) Old 09-17-2003, 01:51 PM Thread Starter
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Re: Spark Knock, Death Knock, valve train knock?????

</font><blockquote><font class="small">In reply to:</font><hr />
how are your rpms at idle? do they fluctuate, are the high? have you checked your spark plugs yet?


[/ QUOTE ]

Who knows, I rebuilt both carbs so I had to readjust the idle on both. And no, I haven't checked yet. I guess that would be a good move before tearing off the intake. (I hate messing w/ that valley pan gasket thing!)
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post #9 of (permalink) Old 09-17-2003, 01:55 PM
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Re: Spark Knock, Death Knock, valve train knock?????

check the plugs, if they are anything but a nice tan color I'd try to figure out why. as for the intake valley pan gasket... try just tightneing down the bolts first before pulling the intake off. you may have some loose bolts is all. but from what I've seen a vac leak usually goes hand in hand with high or fluctuating rpms...
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post #10 of (permalink) Old 09-17-2003, 05:18 PM Thread Starter
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Re: Spark Knock, Death Knock, valve train knock?????

Well, I checked the plugs. They're a nice tan color, and that isn't good. You see normally they would be black with oil and ash. This may be the first time since Viet Nam that this Jeep has had nice clean tan plugs. This seriously is very strange! All I can guess is that there is a vacuum leak that causing this miracle?????????
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