302 "knocking"
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302 "knocking"
'78 302 bored .30 over, new rods, pistons, crank ground .10, verified bearing clearances when assembled.
Less than 50 miles on engine and have developed a tapping/knocking noise from front of oil pan. Only happens when engine is hot (water temp of 195 degrees) and is occurring at a rate that is approximately 1/2 the engine rpm. Cannot always detect it by ear but can by stethoscope and it is isolated to front of oil pan.
Probing the fuel pump, timing cover, distributor, front bearing area confirms that sound is isolated to front of oil pan.
Any ideas?
Thanks in advance.
Less than 50 miles on engine and have developed a tapping/knocking noise from front of oil pan. Only happens when engine is hot (water temp of 195 degrees) and is occurring at a rate that is approximately 1/2 the engine rpm. Cannot always detect it by ear but can by stethoscope and it is isolated to front of oil pan.
Probing the fuel pump, timing cover, distributor, front bearing area confirms that sound is isolated to front of oil pan.
Any ideas?
Thanks in advance.
Fleet Owner
Joined: Sep 2005
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From: Lake Tahoe, Nevada
If you are correct that it is 1/2 engine speed, that would be something cam driven.
Oil pump/ditributor drive? Cam sprocket?
Are you running high compression pistons? High lift cam? Any other mods?
Oil pump/ditributor drive? Cam sprocket?
Are you running high compression pistons? High lift cam? Any other mods?
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Nothing radical. Flat top pistons, mild street cam, 9.4:1 compression. Scope isolates sound to "front" of oil pan. Does not originate in distributor or cam area of block. Oil is 10W-30.
Correct me if I'm wrong but on a four stroke engine isn't cam 1/4 engine rpm? Would really like to know what oil pump rpm is. Suspect that it is 1/2 engine rpm.
Thanks
Correct me if I'm wrong but on a four stroke engine isn't cam 1/4 engine rpm? Would really like to know what oil pump rpm is. Suspect that it is 1/2 engine rpm.
Thanks
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Originally Posted by HemiEater
start pulling plug wires while it running and see if it goes away or changes....
This sound is 1/2 engine rpm and is not detectable with scope while engine is cool.
Thanks
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Postmaster
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most of the time.. if it is a rod bearing , it will knock when it fires only.....and if you pull the wire on that hole it will go away....
cold engine has thicker oil...can't hear it...... once the oil warms up it thins out...
cold engine has thicker oil...can't hear it...... once the oil warms up it thins out...
Last edited by HemiEater; Nov 21, 2007 at 06:18 PM.
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Postmaster
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hook up a timing light....and use every plug wire until you get to the one that lines up the knock with the light and thats the hole with the knock
I'm thinking to much......it's just stuff I would do if it were in front of me.
I'm thinking to much......it's just stuff I would do if it were in front of me.
Fleet Owner
Joined: Sep 2005
Posts: 28,609
Likes: 18
From: Lake Tahoe, Nevada
Bearing clearances verified when assembled. I doubt that a bearing failed in fifty miles.
What was not checked when the engine was assembled? Wrist pins?
Is this a mechanical, cam driven fuel pump?
What was not checked when the engine was assembled? Wrist pins?
Is this a mechanical, cam driven fuel pump?
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Junior User
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Originally Posted by HemiEater
hook up a timing light....and use every plug wire until you get to the one that lines up the knock with the light and thats the hole with the knock
I'm thinking to much......it's just stuff I would do if it were in front of me.
I'm thinking to much......it's just stuff I would do if it were in front of me.
If it is rod knock I suspect that is is coming from the number 1 or number 5 rod as they are closest to front of oil pan.
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Originally Posted by Bdox
Bearing clearances verified when assembled. I doubt that a bearing failed in fifty miles.
What was not checked when the engine was assembled? Wrist pins?
Is this a mechanical, cam driven fuel pump?
What was not checked when the engine was assembled? Wrist pins?
Is this a mechanical, cam driven fuel pump?
All clearances were verified but that doesn't mean that I didn't screw up something.