Engine Overhaul

[siii8873]

I am about to start my engine repairs. This engine has failed crank bearings. I'm confident that all the problems are with the crank bearings. The engine was bored out with new pistons / rings and a replacement RN 8:1 head without many miles on them. The engine developed a knock and when I examined the engine I found a loose flywheel which I think caused the bearing failures.
First question; do I need to remove the head to restore the crank bearings? I do not see a reason that I would have to?
More ?s to follow I'm sure.

[SafeAirOne]

I am about to start my engine repairs. This engine has failed crank bearings. I'm confident that all the problems are with the crank bearings. The engine was bored out with new pistons / rings and a replacement RN 8:1 head without many miles on them. The engine developed a knock and when I examined the engine I found a loose flywheel which I think caused the bearing failures.
First question; do I need to remove the head to restore the crank bearings? I do not see a reason that I would have to?
More ?s to follow I'm sure.

Were the bearings replaced at the same time as the pistons/rings/head? I'm not sure how the loose flywheel relates to crank bearing failure. I figure it'd make itself known before it lead to any bearing damage from being out-of-balance. Perhaps the flywheel was knocking around, causing noise?

At least you can have a peek at the crank bearings without too much trouble (presuming you can get the oil sump off and out of the way).

Anyhow...the crank bearings can be replaced from below.

[siii8873]

PO said professionally rebuilt engine bored out, new pistons, new performance cam, new head.I cannot say with confidence that the crank was done at that time. I will need to look at the receipts again to see if any crank work was done.
I will be opening it up soon for further investigation. Did have a mechanic look at it when the engine started knocking and he informed me that the crank bearings, top only, were wiped.

[Donnie]

I am about to start my engine repairs. This engine has failed crank bearings. I'm confident that all the problems are with the crank bearings. The engine was bored out with new pistons / rings and a replacement RN 8:1 head without many miles on them. The engine developed a knock and when I examined the engine I found a loose flywheel which I think caused the bearing failures.
First question; do I need to remove the head to restore the crank bearings? I do not see a reason that I would have to?
More ?s to follow I'm sure.

No, U can pull the oel pan & inspect the crank & bearings. The thrust of the piston is DOWN when the plug ignites the fire, thus the top bearing on the rods takes the hit & the lower bearing on the main takes it. Pull the pan, pick a rod to check, usually the farthest one from the oel pump.Punch mark the cap B4 removing as they are directional so it goes back on the same rod in the same direction..DO NOT MIX any caps.. U can then push the piston / rod up a bit and feel the crank with your finger nail...No scoring is what U R looking for.Do the same with 1 main, look at the brng in the cap to see the wear, again feel the crank...More accurate testing is coming down the pike, this is just a basic check to try to see where U R at..

[SafeAirOne]

Did have a mechanic look at it when the engine started knocking and he informed me that the crank bearings, top only, were wiped.

Wow. Either he's REALLY good for being able to tell which bearing halves are bad by ear or he's REALLY bad for not replacing the bearings when he had it apart to determine that the top shells were the only ones worn out.


BTW--Before, I meant to say that you can replace the Main & Rod bearings without removing the head. Obviously you'd have to do it from down below.

[Firemanshort]

Food for thought - definately conduct exploratory surgery from below. Pull the oil pan and take a look around the crank.

Take a good sift through the oil in the pan. Is there tons of metal shavings (the remains of a bearing)? When you pull a rod or crank and see a heavily worn bearing.... did all of the missing metal get caught by the oil filter and none of it made its way to the upper parts of the engine (cam and/or rocker shafts).

I wager you could buy a set of rod and main bearing and bolt that puppy back together with no problems - but it is not my wager and not my truck.

[siii8873]

Pulled the pan and examined rod bearings/ crank. Just as noted all the top bearings show wear see picture. I do see that the bearings are marked .010", crank must have been rehabbed when overhauled. The crank journal looks good.
seperate question there is a "62" stamped on engine. What does this mean?

[siii8873]

pictures didn't attach 2nd attempt

[Drain Rovers2]

pictures still not there where is the 62 staqmped on the engine ?

[siii8873]

may have it this time w/ pictures. The "62" is stamped on the flange where the oil pan attaches.

[siii8873]

put engine on a stand and tore it down to the crank. Looks like crank needs to be groung and bearings replaced.
Anyone know the significance of "62" stamped on engine?

[siii8873]

bearing nip

I have a question about part of the proceedure outlined in the green bible regarding crank shaft renewal. I notes to check the bearing nip, torque down the bearing cap, bearings in place, loosen one bolt and check for a clearance within spec. I have my crank at a machine shop where I instructed him to cut it to one of the undersize specs in the book.
I will then determine what size bearings to order based on where it cleans up. I am assuming that with the crank cut and correct bearings ordered that this should be correct. How is it adjusted if not correct? Any insight on this would be appretiated, don't like to assume, we all know what that means.
thanks
Bob

[thixon]

I have a question about part of the proceedure outlined in the green bible regarding crank shaft renewal. I notes to check the bearing nip, torque down the bearing cap, bearings in place, loosen one bolt and check for a clearance within spec. I have my crank at a machine shop where I instructed him to cut it to one of the undersize specs in the book.
I will then determine what size bearings to order based on where it cleans up. I am assuming that with the crank cut and correct bearings ordered that this should be correct. How is it adjusted if not correct? Any insight on this would be appretiated, don't like to assume, we all know what that means.
thanks
Bob

Bob,

The machine shop pollishing the crank should take care of this for you.

Since you asked though, the home mechanic can check the bearing clearance using a product called plastigauge. Its not exact, but pretty close.

[siii8873]

I understand the use of plastigauge and after reading the book again it is used as an alternative to the bearing nip method. The machine shop has the crank only so they cannot make these checks. I am making some assumptions here that if the crank is machined to tolerance and I purchase bearings for that size all clearences will be correct. I will check with plastigauge. I'm more curious about how the nip method works as these checks would not be difficult to make. It seems to me if you torqued down the bearing blocks and there is a bearing clearence of 0.0008"-0.00285" why would a gap occur when one side of the bearing block is loosened?
Took the crank in today.....