Rod Bearing Replacement (in truck???)

[JOJABOY]

Anyone ever tried to replace rod bearings without pulling the motor? Just curious. My buddy replaced the rod bearings on his car with the motor still in the car. Not sure it would be worth the pain in my C20. Which is worse... Pulling the motor? or Removing the oil pan with that cross member in the way?

Either way.....I have a knock and was thinking of taking the pan down and looking at it. Need to reseal the pan anyways. Just wondering if the effort is worth it. Or just pull the engine, do an overhaul and put it back. Hmmmmm

Thoughts anyone?

[71Sixer]

Money well spent to overhaul the engine...more money and time now is less in the long run. My 2 cents

[Ol Blue K20]

if it's knocking most likely scored the crank already, just bite the bullet and pull it.
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[ole dollor]

it can be done, but it would be better to pull it out like others have said. need to give the crank a good look over..

[SS Tim]

May have to resize or even replace a rod and that realization sucks when the bottom is already torn out at great effort. I'd pull it and do what you have to and respray the outside as a visual reward.

[daves72C10D]

If you drop the pan and there is no bearing trash in the oil and the journals look good you can slide the bearing in between the rod and journal.

[Steeveedee]

If you don't have a lot of accessories, that engine can be out in less than two hours. Why would you want to lay in all them drippings, unless your back needs oiling up? I've been there with that, and it ain't worth it.

Before you do that, please describe what the knock is like. It might not be a main or rod bearing, and you might get off easy.

[JOJABOY]

It's an audible knock that can be heard from inside the cab with windows up. When under hood....can still hear the know through the exhaust sounds. Sounds low end and and as if it's in the back on the driverside (#5 or #7 maybe).

I have only had the truck for a few months. I don't have any history on it. I bought it with no carb and had an elderly fella down the street put some majic on it. It runs good. Good idle and strong. It's just knocking.

[geezer#99]

Maybe it's just detonation!
What's your timing set at?

[JOJABOY]

I'm pretty sure it's not detonation. The old fella that put some majic on it really seemed to know something about carburation. He rebuilt my HEI with some custom made weights and springs....totally rebuilt my brand new carb with different jets....said something about drilling out holes 60/1000 inch to get more air flow. Runs like a champ. Just noisey.

[geezer#99]

Custom weights and springs will likely bring your timing curve in way too quick causing detonation.
I had the same on a 396. Thought it was a noisy bearing in the tranny. 500 bucks later same noise. Pulled the timing back a bunch. No noise. Low speed detonation.
Sounded like a rock in a coffee can.
Easy to check. Check your timing and reduce it or plug off the vacuum to your distributor.

[piecesparts]

Question:

Are you absolutely sure it is a rod bearing? If your fuel pump spring is weak, it will knock and it sounds just like a rod bearing. Check it out, before tearing the engine apart.

[TBONE1964]

First of all, I agree 100% with SS Tim, if you hear a rod knocking, the rod needs to be re sized. If you don't do this, your knock will come back sooner than you want it to.

Try this:

One at a time, pull a plug wire and start the engine. Listen for the tone of the knock to change. If the tone changes, then you have a rod knock. The tone will change because the cylinder is not firing. Yes it will still have compression but will sound different with no fire in the hole.

Usually rod knocks are not as noticeable at idle. You need to give it a free rev in park or neutral to really hear it.

Another thing you can check is crack shaft end play. Grab the front of the harmonic balancer and try to push the crank back and forth with both hands. If you can hear a clunk when doing this, then the thrust bearing on your crank is wore.

[joesgreen67]

Originally Posted by TBONE1964

One at a time, pull a plug wire and start the engine. Listen for the tone of the knock to change. If the tone changes, then you have a rod knock.

EXACTLY what I was going to say....TBone is dead on. This check is free and easy. Another way to narrow down what your issue is BEFORE you dig in.

[ole dollor]

and a broken or loose flex plate can knock also, pull the motor and see whats going on . before it destroys its self.