Author Topic: What to do about a wrist pin  (Read 16211 times)

Offline philo_beddoe

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Re: What to do about a wrist pin
« Reply #45 on: March 13, 2017, 09:13:21 PM »
I needed a gm crate 350, got one from summit. $1200, no interest. Runs awesome.
Behold, the day of the LORD cometh, and thy spoil shall be divided in the midst of thee.  Zechariah 14:1

Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #46 on: March 14, 2017, 05:07:11 AM »
links don't work........

Not sure what happened there.  Seems to be fixed now - try again.

Offline VileZambonie

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Re: What to do about a wrist pin
« Reply #47 on: March 14, 2017, 07:14:18 AM »
Sounds like you have exhaust leaks and lifters out of adjustment/worn cam/lifters. I do not hear a wrist pin knock, main bearing or rod knock.
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Offline 82silverado

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Re: What to do about a wrist pin
« Reply #48 on: March 14, 2017, 09:25:11 AM »
 I don't hear a deep knocking from the engine either. Some of the clips I couldn't hear anything abnormal. I don't think that we could hear on video what you are hearing up close. I wasn't sure that we would be able to though. The ne from underneath seems to have the most noise to it.
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Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #49 on: March 14, 2017, 07:45:20 PM »
I don't hear a deep knocking from the engine either. Some of the clips I couldn't hear anything abnormal. I don't think that we could hear on video what you are hearing up close. I wasn't sure that we would be able to though. The ne from underneath seems to have the most noise to it.

Yes, it's definitely more prominent from underneath.  Pretty difficult to hear it from up top.  That may be partly due to fan/accessory noise, but even trying to listen through that background noise, I don't get much from above.  That's why I was suspicious of the lifter hypothesis from the beginning - I'm just not hearing anything emanating from the top end.  When I did the power balance test, I could hear clattering in the heads (not sure why, but something obviously was going on there when I shorted out a cylinder).  That makes me think that if the subject noise was lifter or valve-train related, I should be able to hear it from above.  (Also, the mechanic initially suspected lifters, but ruled that out based on his diagnostic work.)

For some reason the sound didn't come through too well on the clips that were taken inside the cab.  It is definitely audible from inside, though.

You're both correct that the sound is not a deep knock.  It's best described as a tick or a tap. 

I don't think it's an exhaust leak, though.  I've experienced those before, both on my own vehicles and other people's vehicles.  From what I've experienced, exhaust leaks do have a ticking quality, but they also have a "pffft" quality to the sound - like rushing air.  I'm not hearing the "pffft" noise at all.  Also, in my experience, exhaust leaks get noticeably louder when accelerating or when the engine is under a load.  This noise doesn't do that.  Previous exhaust leaks I've had haven't been audible at all at idle; this noise is most audible at idle.  Everything behind the manifolds is brand new with no rust, so an exhaust leak would have to be coming from the manifold gasket, a cracked manifold, or an improperly installed doughnut gasket.  The first two should be audible from above.  And finally, the mechanic does lots of exhaust work (lots of road salt around here; everyone's exhaust system rusts out eventually).  He's heard a lot of exhaust leaks and should have caught it if that's what it was.

Vile - I'm not disrespecting your experience at all; just passing along some information that I probably should have provided before you listened to the video clips.
« Last Edit: March 15, 2017, 06:19:46 AM by Monkey Uncle »

Offline VileZambonie

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Re: What to do about a wrist pin
« Reply #50 on: March 15, 2017, 12:48:50 PM »
I am not disrespected at all so no need for that. I would suggest you buy a mechanics stethoscope and do some investigating yourself. Take the wand off and run the straw around the exhaust manifolds and you'll know it if there is an exhaust leak. Use the stethoscope probe to pinpoint where it is the loudest.
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Offline Stewart G Griffin

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Re: What to do about a wrist pin
« Reply #51 on: March 15, 2017, 08:58:03 PM »
Run it until it quits. 

Offline philo_beddoe

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What to do about a wrist pin
« Reply #52 on: March 17, 2017, 09:22:13 AM »
I agree with stew grif, burn it out, then start fresh with a new crate 350. $1200, no interest, no tax, free shipping.  I got my engine one year ago this month. I just paid it off yesterday. Not one penny interest. Haha, jokes on summit. (Not really, the house always wins)
Behold, the day of the LORD cometh, and thy spoil shall be divided in the midst of thee.  Zechariah 14:1

Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #53 on: March 17, 2017, 05:28:15 PM »
I agree with stew grif, burn it out, then start fresh with a new crate 350. $1200, no interest, no tax, free shipping.  I got my engine one year ago this month. I just paid it off yesterday. Not one penny interest. Haha, jokes on summit. (Not really, the house always wins)

Summit's gone up since you bought yours.  Seems like the cheapest 350 crate is now in the $1,500 - $1,600 range.

Offline 82silverado

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Re: What to do about a wrist pin
« Reply #54 on: March 17, 2017, 07:19:44 PM »
Curious to know if the dust cover has been dropped yet and t/c slid back and motor ran. If you are sure you have no exhaust leaks and it has not been done yet, then that is the next logical step along with the other steps outlined by BD and VZ referencing the power balance test.
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Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #55 on: March 19, 2017, 11:45:28 AM »
Curious to know if the dust cover has been dropped yet and t/c slid back and motor ran. If you are sure you have no exhaust leaks and it has not been done yet, then that is the next logical step along with the other steps outlined by BD and VZ referencing the power balance test.

Discovered that I don't have the right size socket to fit the dust cover bolts.  9/16 is too small and 5/8 is too big.  Is it possible GM could have used 15 mm metric on a TH 350 dust cover?  5/8 will fit the two bolts that attach the support braces to the dust cover, but is too big for all the others.  The bolt heads look a little worn, but not so much that a properly sized socket shouldn't grab.  Of course I don't have a metric socket set.

I know this is very basic stuff for you guys, but anything beyond an oil change and spark plugs is new territory for me.

As noted above, mechanic said he removed the dust cover and inspected the flex plate and torque converter and found no issues.  He didn't say whether he disconnected the TC and ran the engine.

Crawled around under it and listened some more yesterday; confirmed again that the noise is most prominent down low and toward the back of the oil pan/dust cover area, or even the transmission pan area. 

Here's something I haven't brought up before, because I didn't think it was relevant.  But as long as we're being thorough, may as well fill you in.  At some point in the past, the tip broke off of the old transmission dipstick (I stuck a new one in the tube so I can check the fluid level).  Every person and info source I've consulted says that the broken off tip will rest harmlessly in the trans pan until the next time the fluid is changed.  But is it possible that movement of fluid in the trans pan could cause that broken piece to tap rhythmically against the pan, in perfect time with RPMs?  Seems pretty far fetched to me, but as long as I'm grasping a straws...

Offline Irish_Alley

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Re: What to do about a wrist pin
« Reply #56 on: March 19, 2017, 02:53:17 PM »
even if it was to tap theres not enough mass or kinetic energy to make the sound audible over the engine
If you can’t tell yourself the truth, who can you tell it to?~Irish_Alley

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Offline bd

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Re: What to do about a wrist pin
« Reply #57 on: March 19, 2017, 04:16:21 PM »
Converter cover bolt heads are 15 mm (FYI - 10, 13, 14 and 15 mm are common metric sizes used on vintage GM products; 16 mm and 18 mm are less frequently used).  The dipstick "tip" is not the source of the noise you hear.
Rich
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Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #58 on: March 19, 2017, 04:34:03 PM »
Thanks, guys.

Offline Monkey Uncle

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Re: What to do about a wrist pin
« Reply #59 on: April 02, 2017, 02:14:35 PM »
I finally found the combination SAE/metric socket set that I had forgotten I have (Doh!).  Dropped the dust cover, but was not able to break the TC bolts loose.  Either my 3/8 drive ratchet is too short, or I didn't eat my Wheaties this morning.  Probably should have tried tapping the ratchet with a hammer, but I'm always a little nervous about forcing things.  Is there any particular trick to keeping the engine from rotating while trying to turn the wrench?  I could hold the flex plate still with my left hand and push on the ratchet with my right, but couldn't get enough force to break the bolt loose.

I did turn the engine all the way over and take a good look at the flex plate all the way around.  It looks brand new, except for the one chipped tooth that apparently happened when I was getting re-acquainted with how to start a carbureted engine.  Didn't see any cracks.  If the flex plate isn't cracked, and the torque converter bolts aren't loose, is there any way a rhythmic tapping noise that correlates with rpms could be coming from the torque converter or something in the front of the transmission?