Bearing question

[Dan D.]

Re: Bearing question

Thanks Joe,

From what I have read on this forum, Duke has very strong opinions on old small block rods. He says they can and will fail at any time, probably holing the block in the process. I believe he has a replacement rod that he recommends for these engines.

The OP says this is the original engine with 100k miles. And given that he has an undetermined knock, and particles in the oil, he should just bite the bullet and go through the entire engine. No telling what one may find in the process, and losing a born with engine would be a shame.

My 2 cents Joe.

-Dan-

[Domenic T.]

Re: Bearing question

Thanks Joe,

From what I have read on this forum, Duke has very strong opinions on old small block rods. He says they can and will fail at any time, probably holing the block in the process. I believe he has a replacement rod that he recommends for these engines.

The OP says this is the original engine with 100k miles. And given that he has an undetermined knock, and particles in the oil, he should just bite the bullet and go through the entire engine. No telling what one may find in the process, and losing a born with engine would be a shame.

My 2 cents Joe.

-Dan-

Good point, But I have raced these SB chevy engines (stock class) and we beefed them up for street racing.
I have seen the stock engine rods fail by in-experienced driver that tried to push a engine to 10 ,000 and brag about it, or ones learning to power shift. 2 bolt mains were all we had and unless we doubled the HP, they were fine. Starvation of oil on 1 & 2 rod, water in the cylinder, and over revving took rods out.. I simply check each rod on a rod jig and have never lost a rod or 2 bolt main crank. As I said on the other forum today, there were wana be drivers when the SB was the in thing (chevy), the drivers had decals on their windows showing they were running Isky, Crane, etc. The brag was "full race cam", you could be king at the A&W.
I pushed them to the GM limit racing my shadow, strip, and street. Never had a problem, all the problems were caught during check outs when rebuilding.
I doubt that any classic vette driver would do those things. All I had were small blocks with exception of the 348 & 409. Yes, I beat them to death but always paid attention to the power curve charts and factory RPM limits. I have my head bolts heat treated or simply pay attention to how many degrees of turn it takes to get torque. Stretching a bolt is easily detected. Back in the early days the race drivers preffered proven parts and re- machined seasoned parts. I am bound by oath to use new bolts in aircraft engines and will say that the manufacturer has re-calls on new parts, bolts, and other new parts. I personally prefer proven parts that were made here in the US.
If you are going to double the HP, pro race, then by all means change the rods crank case and crank, GM spent millions on the development of the greatest SB ever built and us 2 bit mechanics don't hold a stick to what has been proven to work. Bu Ba can blow any engine rod.
Now, that's just my opinion and what has worked for me as a Chevy mechanic, shop owner, old time drag racer, and FATHER with sons that pushed dads cars when borrowed.

Dom

[Ed K.]

Re: Bearing question

Hey Guys, I'd like to expand on the "knock". It's a heavy clunking sound, not a rattle not a ping. Sounds exactly like and lasts as long (4 or 5 clunks) as not pre-filling the filter during an oil change. Oil is not yet somewhere so it clunks. What clunks when not pre-filling filter?

[Domenic T.]

Re: Bearing question

Ed,
I'm bringing you back up to the top. May not be oil oriented at all. I've found a front pulley that was loose make that noise and be hard to find because the belts were tight. Cam is only held in place by the chain and can move to the cover or plug in the back. The cam lobes are at a slant so they spin the lifter, but that shouldn't be a deep clunk. I didn't see any side wear on your bearings that pointed to them making noise.
What I am saying is that it might be something else attached to the engine.
I saw a bunch of rebuilds sold at the dealership only to knock as bad when done. Ended up being harmonic balancer, main pulley or other components. Just a shot in the dark but knocks (other than piston slap that go's away when warmed up) usually don't come & go.

Dom

[Steven B.]

Re: Bearing question

My bet is on the rod bearing(s). I had a substantial knock in a small block that turned out to be an extremely small spot (about the size of a pencil point) on one Clevite 77 rod bearing. Every other bearing looked perfect. I wouldn't have thought such a small blemish would make such a racket. My knock didn't go away after oil pressure came up on start up however. I wouldn't think you would get as much of a knock if any on a main bearing. I do think you're right to replace all bearings while you have things apart.
Steve

[Ed K.]

Re: Bearing question

All bearings would definitely be replaced and new oil pump installed. Fortunately this all can be done without removing motor. Would like to avoid time needed to remove/reinstall motor and rebuild cost if possible.

[Duke W.]

Re: Bearing question

Thanks Joe,

From what I have read on this forum, Duke has very strong opinions on old small block rods. He says they can and will fail at any time, probably holing the block in the process. I believe he has a replacement rod that he recommends for these engines.

The OP says this is the original engine with 100k miles. And given that he has an undetermined knock, and particles in the oil, he should just bite the bullet and go through the entire engine. No telling what one may find in the process, and losing a born with engine would be a shame.

My 2 cents Joe.

-Dan-

Over the years I know of a number of guys who lost rods, particularly the 283 and early 327 type. I recall Mike Ernst reported losing one on his '57 283/283 FI engine a few years ago. When I had my '63 340 HP rods Magnafluxed #7 had a bad crack on a bolt seat, which is the weakest part of the rod. It could have let go at anytime, and I was lucky to catch it in time.

The second design 327 rods that went into production in '66 have a small "hump" of material adjacent to the bolt seats, which considerably improves their durability.

In order to properly Magnaflux rods the bolts must be removed and this requires that they be resized, and shotpeening is a good idea. Add up the current cost and it is probably greater than the 250 bucks that a set of 3/8"-bolt Eagle SIR5700 rods cost, which is why I recommend replacing the early rods.

As far as the second design 327 rods are concerned, either just check them for dimensional conformity and straightness and use them as is on 300 HP engine or buy the Eagles. The 350 HP engine is "iffy", but 250 bucks for a new set of rods is the cheapest insurance policy you will ever buy for a numbers matching OE block, and you can use the full rev range, if not a little more, with confidence that it's not going to blow up.

Back in the seventies there were few high strength rod options. Carillos were the best, but they were EXPENSIVE! So I bought a new set of OE rods, ground down the forging flash, had them Maganfluxed, shotpeened, and then resized them with higher strength 11/32" bolts. Given the low cost of higher strength rods, today, it doesn't make much sense to rework used rods.

Duke

[Domenic T.]

Re: Bearing question

Duke,
Makes sense to me now. Back then I had more time than $$ and had to do all myself. Thank god all production rods were the same weight unless a balance afterwards. Doing 24 rods at a time made it worth the work, (set up time). Now I own the home I did all that work for and the 250.00 makes sense.

Dom

[John M.]

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

Duke, help me out here with this "bearing crush" deal. I have always checked bearing clearances with plastigage; two 327 builds recently, which requires installing the bearings and torquing to spec with the plastgage on the journal. Then, of course, you have to remove the bearing cap and bearing to make the measurements. The bearings usually stay in place in the block or rod and caps but not always. It's hard for me to see the problem with this pretty much universal technique. Am I missing something?
Thanks,
John

[Duke W.]

Re: Bearing question

When you tighten cap bolts it slightly deforms the bearing and "locks" it in place. That's what's commonly called "bearing crush". Removing the cap to check Plastigage is okay, but it's not a good idea to remove a bearing from the bearing bore after the cap has been initially torqued and then removed.

Reinstalling the bearing halves in the bearing bores and torqueing the cap bolts will not "lock" the bearing in place as securely, and there is a greater chance of a problem down the line.

In my experience the bearings will usually stay in place when you remove the caps to check the Plastigage as long as you handle them carefully.

Duke

[Ed K.]

Re: Bearing question

Any thoughts on what might cause the heavy 4-5 clunks after cars sits a few hours - but then knock gone at any RPM. As Dom said, "Knocks don't come and go".

[Domenic T.]

Re: Bearing question

Ed,
Does this only happen at start up after it sits?

Dom

[Richard G.]

Re: Bearing question

Ed;
Some ideas on the next move might be;

1)Install new bearings and oil pump and start the motor.
It could fix the issue
Check the oil again for debris after 50 miles.
2) If it still knocks;
Now you have an opportunity to try some other ideas to further isolate the issue.
I would pull the belts to eliminate any possibility of the accessory drive system being the source of the knock.
I didn't find where you mention if your car is an automatic or not. If if it is an automatic I would check the torque converter bolts and the flywheel attachment bolts.
3) This the information I am most curious about:
*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.*

Nothing we have seen so far accounts for the debris in the oil. I would for sure check out the oil pump and the screen. They are simple to check, my guess is you have already dismantled the pump for a root cause analysis. If not, do it now and inspect the shaft, gears and the end-clearance. I a lot can be learned from this style inspection. Debris will also damage the gears when it go through the pump. Pull the oil filter apart and check it also. Did you change it when you changed the oil after 50 miles? I assume so. Anything you find will be recent and with luck you might be able to tell if its aluminum, cast or steel.

I would also move the harmonic balancer back and forth by hand, you should be able to feel the slack in the chain by doing this. Just for an additional piece of information to make a decision on where to go from here.

Best of luck.
Rick

[Wally A.]

Re: Bearing question

sure its not piston slap? or wrist pin issue

[Edward J.]

Re: Bearing question

Ed
A knock on cold start up is related to bearing clearance, its looking for Oil to fill the void between the bearing and crankshaft. once oil is introduced the gap it is closed due to pressure and the generally goes away. It does not take but a little wear on bearing surface to cause knock on start. do a close inspection of surfaces of crankshaft if you have any grooves on crank, I would stop wear your at and remove engine. putting new bearings in will only make the knock worst and the new bearings will have gaps between the two surfaces and building up pressure will take just a little bit longer. As a rule of thumb if can your finger nail can feel the grooves across the journals it maybe just that time.