Engine is knocking after 15K miles...
 

This is my first post here as I am brand new to the forum.
If I am posting in the wrong place, can someone direct me to where I should take this question?
I have a 1992 Chevy G20 Van and I put a rebuilt 350 engine in it 2 years back.
The engine has 15,000 miles on it and has run smoothly and without problems.
Suddenly the engine started to knock. This knock occurs when the engine is at the top of first gear, just before it shifts into 2nd. After that the engine is quiet again. If I sit in neutral and raise the rpm the knock will begin to start. I had a mechanic listen to it and he told me I have bad inserts.
So today I have removed the engine from the van (What fun that was! It took me 3 days.)
Can anyone give me some idea of what I should look for after I get the engine opened?
I assume the rod inserts need checking and then perhaps the main journals? This is the first time I have ever been faced with this kind of repair, so I am in rather deep water.
Thanks for any help anyone can shove my way.............pg


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RE: Engine is knocking after 15K miles...
 

I guess no one has ever heard a Chevy knock before, judging from the avalanche of replies received on the question.

Anyway, I now have the engine out, the oil pan off and both heads removed. The engine is clean as a pin inside and the bores look good, as does the lower end.
The only thing found so far is the #2 through #8 spark plugs look the same.....white and clean. The #1 spark plug is jet black instead of white, so that may indicate a problem with that cylinder. I will get a ridge reamer this Friday and then will be able to remove the pistons and rings, as well as check the rod bearings and crank journals...........pg

RE: Engine is knocking after 15K miles...
 

kind of sound's like main bearings ,but definitely check the cam bearing's to make shore they are lined up with the oil holes !torque up the rods when out and check the bore's .

RE: Engine is knocking after 15K miles...
 

I appreciate the reply.
When I get the pistons and rods out I will torque the rod caps on the rods and try to measure the ID of each and compare that to the mic readings I get on the respective crank journals.
I must admit I do not look forward to trying to read the mic to a one-ten thousandth though.

The only thing I have found wrong so far is one of the lifters will not come out of the block. I guess it must have a flare worn on the camshaft side. I will remove the camshaft and then I hope to remove that lifter on the cam side and buy another lifter to replace that one. All of the other lifters came right out...........pg

RE: Engine is knocking after 15K miles...
 

i would say after 15 k milels if it was a new cam it must have run the cam lobe flat and you might need a new cam also !

RE: Engine is knocking after 15K miles...
 

Yes it was a new cam and I know Chevys can eat cams, but it looks to be in very good condition from what I can tell. Still have the cam in the block though..........pg

RE: Engine is knocking after 15K miles...
 

if it wiped out the lifter bad enough to mushroom it ,it probably took out the lobe .

RE: Engine is knocking after 15K miles...
 

Good point old dog!
I will be sure to check the lobe when I remove the cam. It has certainly mushroomed the lifter base because there is no way it wants to come out.
Of course that would not cause the engine knock would it?.........pg

RE: Engine is knocking after 15K miles...
 

yeah they can make a good rapping noise but it would be all the time .