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Old 03-29-2011, 07:34 PM
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Engine noise

1rst gen sbc 350. About a year old, noise recently started. Sounds like a knock, but it's really pronounced at 3500 RPM going down the highway. At idle with the engine warmed up oil pressure sits at roughly 15 psi, give or take a few psi. I had a lot of valve clatter, so I ran through the valves and set them at zero lash. My dad listened to the engine and said if it was rod knock, it sounded like more than one. We had a cold winter and I broke the cam with 30 weight, I did run it cold a few times. Is there anything else I could tell you to help me diagnose the noise? I appreciate your help.

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Old 03-29-2011, 08:05 PM
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can't set hydraulic or solid lifters at zero lash.

which do u have?
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Old 03-29-2011, 11:47 PM
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hydraulic. I use the spin method plus 1/2 turn.
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Old 03-30-2011, 12:58 AM
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i would drain oil into large container then pour oil thru a funnel with coffee filter or paper towel to check for metal shavings. magnet useful also. can cut open filter and check for metal.

what cam?
your sure cam on base circle when you used spin method?
i suppose your familiar w/ spin method on pumped up and bleed down lifters?
1/2 turn is conservative but must be careful about increasing preload; must be familiar w/ valve piston clearance, etc. b4 pushing preload too much.

sometimes lifters can loose adjustment due to nut backing off, or ra stud creeping up. can reverse check lifter adjustments to make sure still at 1/2 turn.

if u have cut top vc u can touch ra and noisy one will shock. can verify all getting oil. can also do a hot adjust if lifter tick is a suspect.

spark knock possible? knock same in neutral as when lugging uphill? higher octane and timing can cure spark knock; you probably already know.

rod knock can be result of running engine w/o oil to infected bearing. knock can be heard in neutral and sounds more ominous than lifter tick. once cause of rod knock corrected it is possible to drop pan and install new bearings for not too much dough.

stethoscope may provide clue.
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Old 03-30-2011, 04:39 AM
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Loose torque converter bolts sound like a rod knock. Also a cracked flex plate does to. They crack around the outside of the crank bolts.Is your flex plate new?.As said a stethoscope is cheap and can be a big help in finding noise source.
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Old 03-30-2011, 11:40 AM
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I'm running a voodoo 60102. I have screw in studs with guide plates. I may have gone a little tighter than that with my rockers. I'm almost positive it's a rod, I'm just trying to think of everything before I go inside. I did recently change my oil and I could see metal in it, very fine metal. Almost like a shimmer in the oil. I didn't think too much of it considering I recently installed a new cam and lifters.
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Old 03-30-2011, 11:46 AM
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Quote:
Originally Posted by RotorHead
I'm running a voodoo 60102. I have screw in studs with guide plates. I may have gone a little tighter than that with my rockers. I'm almost positive it's a rod, I'm just trying to think of everything before I go inside. I did recently change my oil and I could see metal in it, very fine metal. Almost like a shimmer in the oil. I didn't think too much of it considering I recently installed a new cam and lifters.
Sounds like you spun a bearing. JMO Is it popping back through the carb or anything ?



Cole
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Old 03-30-2011, 12:45 PM
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Update

ok, I honestly have been thinking it was a spun bearing too. But now I think otherwise, I originally set my lash with the spin method. At the time I don't think I was thinking about lifter bleed down. I just now ran through all my valves again with the engine running and they were all about 2 turns too tight. I loosened them until they clacked then went between 1/2 and 1/4 turn. I also backed down my timing by a degree leaving my initial at 16 and my total at 37. I went for a ride and didn't seem to hear the knock anymore. The thing I don't understand is, why would valves being tight cause a knocking noise? The valve slamming down on the seat? Oh fyi, My oil pressure at operating temp is 12 psi @ 600 rpm and between 40 and 50 psi at cruise.
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Old 03-30-2011, 12:56 PM
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Quote:
Originally Posted by eloc431962
Sounds like you spun a bearing. JMO Is it popping back through the carb or anything ?



Cole
perhaps improper bearing installation, clearance, alignment, switched bearing caps?

can you verify cap address if they are not stamped?
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Old 03-30-2011, 01:01 PM
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Quote:
Originally Posted by RotorHead
ok, I honestly have been thinking it was a spun bearing too. But now I think otherwise, I originally set my lash with the spin method. At the time I don't think I was thinking about lifter bleed down. I just now ran through all my valves again with the engine running and they were all about 2 turns too tight. I loosened them until they clacked then went between 1/2 and 1/4 turn. I also backed down my timing by a degree leaving my initial at 16 and my total at 37. I went for a ride and didn't seem to hear the knock anymore. The thing I don't understand is, why would valves being tight cause a knocking noise? The valve slamming down on the seat? Oh fyi, My oil pressure at operating temp is 12 psi @ 600 rpm and between 40 and 50 psi at cruise.
hope it didn't make a kissing sound.

37 advance is pretty high for many engines.

did you rule out spark knock?
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Old 03-30-2011, 01:38 PM
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Quote:
Originally Posted by 001mustang
perhaps improper bearing installation, clearance, alignment, switched bearing caps?

can you verify cap address if they are not stamped?
No i can't can you ? that's why i alway's mark mine before i pull them.
There are way's to determine where they do go if they get mixed up.
But i mark mine everytime unless already marked from someone else before.
And i double check anyway.

Cole
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Old 03-30-2011, 01:42 PM
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If you go to tight on the valves then the valve will hit the piston, And can cause major damage like a broken valve and yes you will hear a tapping noise if they are to tight. JMO


Cole
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Old 03-30-2011, 04:21 PM
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knock

one way to tell if you have a bearing going out is to pull a plug wire off, at the distributor so there is less chance of a shocking experience, with the engine running. if the knock goes away or changes a bunch then that is the cylinder in question. i would also do the oil drain test and cut the oil filter apart to see what is in there. drain the oil into a nice clean container and then, under a good light, swirl it around with a screwdriver or something while you watch for metallic swirls. cut the filter apart on a nice clean white paper towel or the like. see what it trapped and go from there. good luck!
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Old 03-30-2011, 04:51 PM
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Quote:
Originally Posted by dsraven
one way to tell if you have a bearing going out is to pull a plug wire off, at the distributor so there is less chance of a shocking experience, with the engine running. if the knock goes away or changes a bunch then that is the cylinder in question.
i forgot about that one.
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Old 03-30-2011, 04:56 PM
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Quote:
Originally Posted by eloc431962
No i can't can you ? that's why i alway's mark mine before i pull them.
There are way's to determine where they do go if they get mixed up.
But i mark mine everytime unless already marked from someone else before.
And i double check anyway.

Cole
can normally tell if rear end caps mixed up.

not sure about crank shaft and connecting rod caps.

suppose you could align bore block if crank caps mixed up; perhaps another way?
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