Forensics - Block

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Whoa ... Stripped block on the engine stand ... pistons, rods, crank, gears, cam, bearings ... all scattered around the shop... How'd THAT happen??

Well, because you are reading this ... it didn't! Congratulate yourself, refill your coffee mug and let's get back to the project!

Continuing our methodical tear down, our next task (with the engine rotated bottom end up) is to remove the oil pan...

Before you remove the pistons

Inspect the top of each cylinder bore for a ridge
if a significant one is present, ream the ridge off before removing the pistons, failure to do this could damage the pistons by breaking the "lands" between the piston rings as you try to drive the pistons out past the ridge where the rings usually stop.

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Remove piston rod caps & pistons

Make sure you have a system for keeping them identified -- Pistons must remain with their respective rods and bearing caps!

Inspect bearings and journals for scoring
Remove pistons, remove/discard old rings

Inspect for damage. As you can see, one of our pistons (#6) has significant damage. Those pieces had to go somewhere, so we will have to be on the look out for damage they caused during their "escape." Lucky for us, the cylinders all passed the check for taper and wear (see below) so we didn't have to do any machining to the cylinders. The replacement stock piston we used is a Sealed Power 92P.

Clean the tops of the pistons to look for oversize markings -- that way you will know if the engine has been rebuilt before.

Separate pistons & rods

Use a punch held in a vise to hold the piston by the wrist pin to avoid bending the rod

After removing the rods, remove the bearing inserts and check them for scoring. On the back of the bearing shell there may be markings indicating which undersize they are. If there, that information will tell you what size the crankshaft was ground to when the engine was last rebuilt.

Check the inside diameter of the big ends of the connecting rods. Remove the bearing shells, torque the nuts to their normal specification (40 ft/lbs.) and measure the diameter with an inside micrometer. It should be round, and within 1/2 thousandth +/- of 2.437 inches (for a 261).
Be sure to use an inside micrometer -- a dial caliper or a digital (even my $300.00 Starret) just isn't accurate enough to check a connecting rod. An easy way to check the accuracy/precision of your micrometer is to measure a drill bit -- a 1/2" bit, checked across the cutting edges, not the shank, will check within .001" of .500.

If the rods are stretched or out of round, the oil clearance on the bearings won't come out right -- you need to get the rods reconditioned by a machinist set up to do that as it is not something you can do with a round file or even with a regular lathe. This is done by machining down the mating surfaces between the rod and the cap, and then using a rod reconditioning hone (like a Sunnen) to make the hole perfectly round again.

Harmonic Balancer

Use a puller to remove the harmonic balancer.
Be careful that the puller yoke bolts don't go too far into (and beyond) the balancer or they will damage the timing cover.

Timing Cover

Remove the timing cover.
Remember that there are two bolts holding the cover from the back side of the front main bearing cap.

Main Bearing Caps

Remove the oil pump assembly
Like the rods and caps, you will need to carefully identify each main cap and it's correct positioning. Use tags to identify each and take a picture.
Then, remove the caps one by one. If you want to be really scientific, check the torque on each bolt before you remove it. Mains should be torqued at ~ 95 - 100 ft-lbs
Check that the caps & bearings actually match the block -- Why is this important? Read this.
Place each tag in a ziplock baggie with its respective cap and bolts, and set aside.
Inspect each main bearing cap & inspect the bearing for scoring.

Before you remove the main bearing caps, make sure you identify each one for correct reassembly when the time comes. Use that ever present cell phone camera (like we did) to take a picture with the caps in place, with their respective tags and showing the correct orientation. Then, place each cap in a ziplock baggie with its tag.

Crankshaft

Remove crankshaft and visually inspect for obvious damage (scoring, for example) -- scoring that will catch a finger nail dragged across it is a problem and means grinding is required.

Measure all journals for wear. Stock measurements for the main journals are (in inches):
- #1 Main (front): 2.6835 - 2.6845
- #2 Main: 2.7145 - 2.7155
- #3 Main: 2.7455 - 2.7465
- #4 Main (rear): 2.7765 - 2.7775
- All rod journals: 2.3110 - 2.3120

Subtract 10, 20 or 30 thousandths for undersize standards. If outside of the parameters, you will need to regrind. If outside of the 30 thousandths parameter, you need a new crank shaft.

Remove crankshaft timing gear.

Cam shaft

Remove cam and inspect lobes, journals and bearing surfaces.
Remove the cam timing gear. If trashing cam, leave timing gear on - you won't need it, anyway.
If you decide to get a new camshaft, you will also need to get new lifters.

Use the Cam Bearing driver to remove the cam bearings. You will need to remove the plug at the end of the block to access the cam bearings (looks like a freeze plug at the back end of the block).

Lloyd checks the cam bearing journals for wear. It failed.

Jerry checks the crankshaft main journals for wear ... They are still within spec for standard sized bearings!

Camshaft bearing journal sizes (See pg. 8-22 in the Shop Manual)

Front: 2.1537 to 2.1547 inches
Front Intermediate: 2.0912 to 2.0922 inches
Rear Intermediate: 2.0287 to 2.0297 inches
Rear: 1.9662 to 1.9672 inches

If the journals exceed .001" out of round, the camshaft should be replaced

Visually inspect cylinder walls for scoring and ridges
Obvious scoring, or a ridge at the top of the ring travel, may indicate a need for honing or ridge reaming. But hold that thought! Before you do anything, you have some other measurements to take.
Measure the bores of each cylinder. Standard diameter of the bore is 3.75 inches. If the diameter is 10, 20 or 30 thousandths more, than it has been bored out. If your measures exceed those standard sizings, you need to rebore. If you are already at 30 thousandths over, you will need to resleeve the cylinders to save the block.
To check for cylinder taper, read this Tech Tip

If bore and taper all pass, then maybe all you need is a little honing and reaming to eliminate some scoring.

We're addressing the scoring in #6 caused by the pieces of the piston making their escape.

Remove the two main oil gallery plugs

One at both ends of the block.
These will be in very tight and may require assistance from the "gas wrench" (i.e. heat) to remove.

Cylinder block front end plate

Remove the front end plate

Remove the timing gear oil nozzle
Clean both thoroughly and set aside (keep all screws with them)

We' didn't have an Allen key to fit the galley plugs ... so we made one.

Road tube baffle plate

Remove the baffle that prevents the crankcase oil from splashing out of the road draft tube.
It is held on by two sheet metal screw from the outside of the block.

Freeze Plugs

Remove the freeze plugs from the block
Use a punch on one edge to knock the other edge out and then grab with vice grips and yank!
Yes, you will destroy them. You will be replacing them anyway. Try to find brass replacements, not steel.

Congratulations!! Your engine is completely disassembled. If the block needs professional machinist attention, now is the time to get that done. As well, anything else that needs machining (crank shaft, rods, cam) should be sent off at this time, too.

WARNING -- Be prepared for a shock. Machine shop work of this sort, especially if the block needs to be cylinder bored and align bored, can cost some real money. Start prepping your significant other/accountant now ... ;)

Also, while everything is off getting work done, you can start hunting up all the other replacement parts you are going to need. Don't order bearings, rings, etc until the machinist tells you how much things have been resized, though.

And when it all comes home, we can start the next phase ....

Cleaning!