92 1500 Loud Tapping Noise when accelerating

[robvas]

Looks like a typical 200k SBC timing chain

[ifixedit]

Yeah, I hate to say it, but it doesn't look too good. Looking over the pics again I can see the circular wear pattern out towards the end of the crank snout indicating the balancer has been rotating back and forth on the end of the crank which would take out the key-way. From the marks and pitting it looks like it's been doing that for quite some time and something finally moved enough to cause it to make the noise you heard. Was probably the balancer banging back and forth on the loose key-way. You might get lucky enough to clean up the key way, secure a new key in it, and find a good balancer (as I'm sure the one that came off is junk) and put it back together. If any part of it is questionable though, how long it will last that way is a crap shoot at best. The balancer has got to be on tight and secure as they are what absorbs the rotational forces and pulses of each firing, something a loose or questionably secured balancer will not handle for long.

Edited November 13, 2015 by ifixedit

[Jared Stangenberg]

I took some pictures of the crankshaft as it was, and then wiped it clean. That's when I realized that it had been previously repaired with what appears to be JB Weld. The harmonic balancer didn't look too bad though, but that's pretty irrelevant at this point.

[ifixedit]

Oh great, JB Weld! Someone did the old quickie fix job and sent it down the road. From the picture the key way doesn't look all that bad. Get the lower gear off, get what appears to be the remaining portion of the old key stock out of the slot and see what you have. If the slot is mostly straight and not too damaged you may be able to clean it up with a small file, get a new key, make sure it fits snug in the slot and then closely inspect the slot in the balancer as well. Since it's a lot tougher to change a crankshaft, at least make sure the slot in the balancer is perfectly straight and undamaged. If it's at all questionable find a new balancer. It looks like whoever did the previous lousy repair job was either in a hurry or was being lazy and was too cheap to go get a new key. You may be able to save it!

Edited November 14, 2015 by ifixedit

[ifixedit]

Now that I have a chance to look over your latest picture again this morning on a larger screen, it appears to me anyways that on the later SBC's that they incorporate 2 separate keys, one for the lower timing chain gear and one for the balancer, my old 350 only uses one key for both. In any case neither key are really sticking out high enough to secure the gear or the balancer, and both could be easily sheared which seems to be the case anyways for the balancer, it looks like the key was sheared off at some time in the past and the balancer spun on the end of the crankshaft. Both keys certainly look like they've allowed movement of both the gear and balancer. Also note the gap between the key and the inside of the key-way in lower gear, that gear is ready to shear off the key as well and I can see damage to the gear key way, everything has been moving around and it's all a pretty sloppily assembled situation.

 

Again, if you can get both keys out and clean up the key-ways (and that isn't JB Weld forming part of the key-way) and get the correct size keys fit in, with a new timing set and an undamaged or new balancer as well, you may be able to save it.

 

Keep us posted.

[Jared Stangenberg]

I've had zero luck getting the keystock out. I'm afraid I've found out why it was fixed with JB Weld before.

I've tried pulling, taping one end with a punch, using a torch, and PB Blaster but nothing has got it budge. I'm going to keep trying for a few more days before I concede defeat.

[ifixedit]

Yeah, sorry to hear this, what a mess. I'd be trying the same, get under the front edge of the key with a punch or better yet some kind of punch with a narrow flat end that fits in the key-way, that key can't be stuck in there that firmly. Unfortunately, it does look though like the end of the crank is pretty boogered up and the key-way itself is ruined. Looks like at some point by the evidence of the JB Weld that the balancer completely spun all the way around on the end of the crank, taking out the key-way in the process and it really messed up the entire end of the crank. Perhaps time for at least a different short block? That or you do a budget repair, find a good used crank, yank the engine, replace the crank, rod and main bearings, timing set, etc.? Either way it's gonna be a hassle at this point.

[Jared Stangenberg]

I tried getting the key out again with no luck. I can feel an imperfection going full circle around the end of the crankshaft, so it's probably not worth the effort of removing the key.

I'm evaluating options right now as far as rebuild v replace. If I do a rebuild, I want to be fairly thorough.

[Jacob spencer]

I have the same exact issue. I have a 1994 Chevrolet blazer 5.7 v8. Just curious if you resolved the issue I would appreciate any assistance 

[Reginald moore]

Jared,

Did you figure out the problem? i have the same issue? 94 K1500

[Reginald moore]

Jared,

Did you figure out the problem? i have the same issue? 94 K1500

[Lisa207]

I know this is an old post, but did you ever find out what the issue was? I have a 92 Winnebago motorhome with a Chevy 454 and it just started making what sounds like the same noise on your video! Thanks in advance! Lisa 

[Lisa207]

On 1/20/2020 at 7:14 AM, Jacob spencer said:

I have the same exact issue. I have a 1994 Chevrolet blazer 5.7 v8. Just curious if you resolved the issue I would appreciate any assistance 

I know this is an old post, but did you ever find out what the issue was? I have a 92 Winnebago motorhome with a Chevy 454 and it just started making what sounds like the same noise on your video! Thanks in advance! Lisa 

On 1/20/2020 at 7:14 AM, Jacob spencer said:

I have the same exact issue. I have a 1994 Chevrolet blazer 5.7 v8. Just curious if you resolved the issue I would appreciate any assistance 

 

[Lisa207]

On 1/20/2020 at 6:41 PM, Reginald moore said:

Jared,

Did you figure out the problem? i have the same issue? 94 K1500

I know this is an old post, but did you ever find out what the issue was? I have a 92 Winnebago motorhome with a Chevy 454 and it just started making what sounds like the same noise on your video! Thanks in advance! Lisa 

[Lesliechevy95]

Anyone ever figure out this problem because my 95 Tahoe is doing the same thing