Engine Removal, Rebuild, and Re-installaion

[Jamesp]

Though the lower end looked almost new when it was opened up (including what appeared to be machining chips), due to mileage, and the failing AOS, there was plenty of oily carbon built up on the pistons. Cleaning it was a challenge. Various hydrocarbon solvents (Chem tool, carb cleaner, brake cleaner, lacquer thinner, etc.) were tried with limited success, the best success came with Chem tool. After doing a load of research a two step process seemed easiest. Buy an empty paint can and soak the piston in Chem tool overnight. After a little scrubbing with a plastic brush only a thin tan build up was left, which turned out to be water soluble. Scrubbing that with a hydrocarbon thinner has very little effect. Some soap and water (wrist pin and rings removed) with a little baking soda cleaned it right up. Rinse the heck out of the bare piston in hot water, dry completely with a lint free towel, Make sure water is out of every crack and crevice. Hit it with WD 40 just to be sure no water is left behind, then soak it with Mobil 1. Or the pistons could just be sent out for cleaning, but where's the fun in that?

[Jake Raby]

B12 is by far the best for this outside of an ultrasonic cleaner..

Meaure those cylinders with a dial bore gauge from different axis and at 3 points top to bottom and look for taper and out of roundness. Guilty until proven innocent!

[Jamesp]

Another tool to buy! One of the perks of doing anything yourself. Looks like a dial bore gauge will join the collection. Having the gear carrier and crankshaft out of the car its time to replace the main and thrust bearings. This engine was a daily driver, mainly freeway with 120K miles. The previous owner drove semi aggressively in Houston traffic and was a stickler for oil changes with the Porsche dealer. As the pictures show, the mains were shot with the babbitt missing in some spots and the backer worn clean through to the steel on at least one edge. The crankshaft mains were not scored and actually looked great so they got a light polish. My takeaway from this is the recommended lube results in worn out main bearings at 120K for a car driven mainly in top gear. The rod bearings, though not as worn as the mains, were also replaced.

[Jamesp]

The IMS bearing failed on this engine. Using this and other forums, the cause of bearing failure appears to be related to loss of lubrication. The root cause of the lubrication loss appears to be due to differential pressure created by the IMS tube heating and cooling pumping engine oil through the IMS bearing. Venting the IMS tube eliminates this, and should allow the grease sealed in the IMS bearing to remain with the bearing. The "new" used IMS shaft is from Ebay, and the original bearing with buna-n seals was replaced with a Nachi 6204 2NSE sporting full contact Viton seals. The bolt is from the Pelican Parts kit. A vent hole can be seen drilled between the teeth of the camshaft drive sprocket. Another is drilled in the same place 180 degrees out from the first hole.

[woodsman]

Great thread- thanks for sharing. Is the replacement bearing a 'standard' bearing in all other ways and is it a single-row? Did the tractor really pull the car?

[Jamesp]

The replacement bearing is similar to the original bearing. Both are 6204 sealed bearings. "6204" is bearing speak for a single row deep groove ball bearing of a certain size. After that there are other things to consider. The original bearing appeared to be a 6204 "N", or "0", meaning a standard clearance bearing. The bearing code was partially outdated so decoding it took some guesswork. It was also sealed on both sides, but interestingly enough, reading the bearing number embossed on the side seals, it should have been sealed on only one side. Life's little mysteries. The seals (more choices) were Buna n full contact seals. Buna n itself comes with different material properties depending on the blend used to make it. The replacement bearing is a 6204 C3 which means it should have more clearance than an "N". The C3 clearance is used in high temperature environments to maintain clearance under thermal distortion. This bearing was also being marketed as a high temp bearing, so the grease inside should hold up to higher temperatures along with the Viton seals. The tractor can pull a plow, the car was no problem. So tonight new timing chains, a new timing chain guide rail, and a new timing chain pad were installed. :dance:

[woodsman]

Wow those chains look HD compared to what I've seen in other engines.