Bearing question

[Ed K.]

I would appreciate assessment of the bearings in the attached 2 pictures.

I'm unsure whether to completely rebuild my 64 Corvette small block engine or just replace the bearings. It's 100,000 mile numbers matching engine, never been apart and runs great. Not a track car or hyper street - just a sunny day very clean driver. Never beat on. Have car for 32 years

Due to brief start-up knock and very fine particles in the oil, I removed oil pan with engine in car. Oil pan is removable in mid-year Corvettes without yanking engine. Visually cam lobes and crank journals look excellent. Crank looks clean, no grooves as seen in bearings.

Engine knocks only at start up after car sits for a few hours - 4 or 5 knocks occur (sounds similar to knock when not pre-filling filter during an oil change). Oil pressure good at idle and high rpm, no knocking at any speed or RPM.

Opinions are appreciated.

[Edward J.]

Re: Bearing question

Ed, looking in the bottom of oil pan of a 100k engine you will likely see some bearing material- normal. since your at the point of looking for a problem with start-up I would just install a new set of engine bearings and rear seal, Its certainly cheap enough. what do you have to loose. the bearings show minor pitting and wear the ones shown, maybe along the way you may see something with one of the others. GM steel cranks were really hard and rarely show wear. use bit of fine emery cloth to clean up any problem areas.

[Ed K.]

Re: Bearing question

Ed, looking in the bottom of oil pan of a 100k engine you will likely see some bearing material- normal. since your at the point of looking for a problem with start-up I would just install a new set of engine bearings and rear seal, Its certainly cheap enough. what do you have to loose. the bearings show minor pitting and wear the ones shown, maybe along the way you may see something with one of the others. GM steel cranks were really hard and rarely show wear. use bit of fine emery cloth to clean up any problem areas.

Thanks for jumping in. I noticed bearing material in catch pan as changing oil. So, completed oil change, drove about 50 miles and dumped oil again into catch pan. Again found particles

[Joe L.]

Re: Bearing question

I would appreciate assessment of the bearings in the attached 2 pictures.

I'm unsure whether to completely rebuild my 64 Corvette small block engine or just replace the bearings. It's 100,000 mile numbers matching engine, never been apart and runs great. Not a track car or hyper street - just a sunny day very clean driver. Never beat on. Have car for 32 years

Due to brief start-up knock and very fine particles in the oil, I removed oil pan with engine in car. Oil pan is removable in mid-year Corvettes without yanking engine. Visually cam lobes and crank journals look excellent. Crank looks clean, no grooves as seen in bearings.

Engine knocks only at start up after car sits for a few hours - 4 or 5 knocks occur (sounds similar to knock when not pre-filling filter during an oil change). Oil pressure good at idle and high rpm, no knocking at any speed or RPM.

Opinions are appreciated.

Ed------


What is the stamping on the rear of the bearing shells for both the rod and main bearings? A photo would be best.

[Duke W.]

Re: Bearing question

When I disassembled my '63 340 HP engine at 115K miles, the OE Morraine 400aluminum bearings looked near new and reusable, but once you remove them you loose the bearing crush, and they should be replaced.

It looks like yours have been damaged by particle contamination, and I recommend you replace them. The Morraine 400 aluminum bearings are long gone. The were very hard, fatigue, and wear resistance, but didn't have good embeddability. Typical replacement bearings are of the "trimetal" type... not quite as strong, but better embeddability.

You should also determine where the particles are coming from. Normal oil filter change intervals should prevent this type of damage unless there is something in the engine that is disintegrating, usually a stamped steel part, so carefully check things like the oil pan baffle, pickup, and any other stamped steel parts for broken welds or other signs of damage. Also, remove and disassemble the oil pump for inspection.

Duke

[Ed K.]

Re: Bearing question

Yes I definitely plan to replace them. Will look for source of contamination. OIl & filter changed twice yearly, within approximately 300-400 mile intervals. Previously never checked oil this closely but the start-up knock led to examination. Changed oil and filter (stock canister filter) drove about 500 miles and again found particles.

[Ed K.]

Re: Bearing question

Car and bearings at my technology teacher son's school on lift. Hope to get photos tomorrow.

[Richard G.]

Re: Bearing question

Sounds like all the rods and mains were removed but only pictures of one of each.
I am assuming the ones pictured were indicative of the rest or were the worst looking of the bunch.

A knock could possibly in the piston wrist pin.
Unlikely I know, but there aren't any indications of excessive clearance in the rod bearings so one has to wonder where the noise is coming from?
I agree with Ed and would like to see pictures of the backside of the bearings. Not for any identification marks but to inspect the pattern on them. Patterns on the back of the bearings can help identify where the issue might be located.
If you can't find a definitive answer I would rebuild the 327.
I say that for a couple reasons:
By the time one finds the culprit you are so far into it one might as well freshen everything up.
That coupled with the high value block you want to protect at all costs.
Knocks are just scary.
Rick

[Dan D.]

Re: Bearing question

64 Small blocks still had the weak rods. At 100k miles, they should be replaced before you lose the engine.

-Dan-

[Domenic T.]

Re: Bearing question

Ed,
My answer is not about the knock but the bearing pits. The pits look like corrosion pits and years ago an old engineer told me that unburned gasoline & oil sitting would cause corrosion. Guys used to rev their motors up and turn the key off for some reason and the gasoline that was sucked in with the ignition off would seep past the ring gaps and into the oil. If the engine sat for a long time the corrosion would happen.
Now there were engines that intentionally had gas injected into the oil in cold climates to thin the oil out, they were required to run for a certain period of time to evaporate the gasoline out of the oil.

Dom

[Joe L.]

Re: Bearing question

64 Small blocks still had the weak rods. At 100k miles, they should be replaced before you lose the engine.

-Dan-

Dan------


Yes, the pre-1968 small block rods were definitely not as good as the 1968+. However, one thing to keep in mind is that all small block connecting rods were forged steel. Many other engines of the day used cast iron connecting rods, Buick being one.

The best current small block rods are the forged powder metal. They're at least 2 times stronger than the best forged steel small block rods (1970-81 L-46, LT-1, L-82). However, GM does not offer them for pre-68 small blocks. I don't think anyone else does, either.

[Guest]

Re: Bearing question

I would appreciate assessment of the bearings in the attached 2 pictures.

I'm unsure whether to completely rebuild my 64 Corvette small block engine or just replace the bearings. It's 100,000 mile numbers matching engine, never been apart and runs great. Not a track car or hyper street - just a sunny day very clean driver. Never beat on. Have car for 32 years

Due to brief start-up knock and very fine particles in the oil, I removed oil pan with engine in car. Oil pan is removable in mid-year Corvettes without yanking engine. Visually cam lobes and crank journals look excellent. Crank looks clean, no grooves as seen in bearings.

Engine knocks only at start up after car sits for a few hours - 4 or 5 knocks occur (sounds similar to knock when not pre-filling filter during an oil change). Oil pressure good at idle and high rpm, no knocking at any speed or RPM.

Opinions are appreciated.

I would check the furthest away rods and main bearing from the oil pump and see how they look

[Ed K.]

Re: Bearing question

Hey guys, 5 pictures but site limits photos to four. So I'll post 3 followed by 2nd post with 2

[Ed K.]

Re: Bearing question

[Joe L.]

Re: Bearing question

Ed-------F


From what I can see of them, these appear to be original GM Moraine bearings. These are a premium aluminum bearing. They're no longer available from GM. I recommend Federal-Mogul "AP" series premium aluminum bearings for replacement.