Disassembling the engine

Taking apart an old car is like restoring an old house.  You  always are going to find something unexpected.  Rarely is that unexpected item good.  Taking apart a Model T engine is pretty easy if following the Model T Service Manual, but there are three points along the way that can really give a person headaches.  

The first is when you remove the top of the engine.  The early Ford cars had "flathead" engines where the top of the engine is a cast iron piece that is domed for the top of each of the four piston's combustion chambers.  The top has no moving parts; just four threaded spark plug holes and holes for the bolts to hold it to the engine block.  It is also hollow to allow the engine coolant to circulate and cool it.  

It is the long bolts that hold on the head that can cause a headache if they snap off, requiring care to drill out and remove the broken bolt.  I watched a YouTube video of a guy disassembling a T engine and was using a powered wrench to remove the bolts.  No, no, no!  It was not surprising that he snapped one or two of the bolts.  I did what I could to prevent the problem by spraying liquid wrench on the bolt heads weeks before removal, along with carefully tapping on the bolt heads with a peen end of a hammer to break any rust in the threads.  Fortunately all 15 bolts came out without breaking, so I could proceed to the next hurdles.

These hurdles occur when taking apart the transmission, where the mechanic needs to remove parts that have been pressed onto a shaft.  The first is the "clutch drum", which is like a small open cylinder where the clutch plates are located.  A very strong, specialized puller is needed to remove it.  Sometimes they are stuck on so bad that heat, otherwise know as a "fire wrench" is needed.  Ford sold a special puller for removing it, but it is flimsier than an aftermarket puller made back in the day by the Stevens company.  The Stevens pullers are being reproduced today and I used one to successfully pull off the clutch drum.

The last hurdle was removing the transmission drive gear from the transmission shaft.  This time I used an original Ford puller specifically designed for the job.  This 100 year old puller worked flawlessly.  Whew, all hurdles cleared and now I could now finish the job.

The rest of the engine disassembly was uneventful, but it was at this stage that I found the unexpected surprises.  The first was some scoring on a couple of the cylinder walls caused by debris getting caught between the piston rings and cylinder walls.  A Model T does not have an oil filter systems like modern cars, so any contaminants in the oil will happily go where ever the oil is flung and will do what it can to cause damage.  One of must have aftermarket items developed during the T era was a screen trough with a magnet at the bottom that is installed just below the access panel on top of the transmission.  Because the Model T engine and transmission share the same oil, the oil flung by the spinning transmission drums ends up going through the screen trough.  Any metallic debris or other pieces of crud get caught by it.  The magnet attracts any of those iron based particles to prevent them from escaping the trough.  

Every T owner should have one of these low cost transmission screens installed to protect their engines.  For some reason, this engine didn't have one installed.  The scoring looked worse than it the actual depth of the grooves, but it would still need to be removed.  That meant honing or likely boring out for an oversized piston.  Speaking of pistons, the ones in the engine were original style cast iron pistons.  Why aluminum pistons were not installed at the last rebuild in 1971 is unknown.  I planned on replacing them with lighter aluminum pistons, which most people use now when rebuilding a T engine.  Their main benefit is less wear and tear on the engine due to their lower mass.  The best news was that the crankshaft measured out to "standard" dimensions, meaning that it does not need to be ground down to a smaller set diameter, usually .010, 0.020 or more inches below standard diameter.

The scored cylinders and crud on some of the exhaust valve seats explained the very low compression that I measured before removing the engine.  The valves seats will be reworked at the same time that the cylinders are bored out.  No big deal, and I pretty much expected that I would need to do the cylinders and valves anyway.  The real unexpected surprise was found on the engine block.  The engine block has three thick webs that hold the crankshaft while it rotates.  Two of the web flanges had a piece missing that looked like something took a "bite" out of them.  This appeared to have happened long ago, as there was no cast iron debris was found in the oil or oil pan when it was removed.  

I consulted with a couple of expert Model T engine rebuilders to get there thoughts on what to do.  Neither was concerned about the missing flange pieces, as the web on the left next to the engine flywheel and has the highest load.  One of the experts did notice a slight crack in that web when looking at the picture.  He had a good eye, as I did not see the crack until looking at the block more closely.  The crack was different than what occurred in other two flanges, but could have been caused by a change in overall block stiffness due to the missing flange pieces.  It is impossible to know if it was caused by that, but the block needed to be fixed.

After further discussion with them and another shop about possibly mechanically "stitching" the web crack, the best course of action was to have the block brazed by a professional.  This required heating the block in an oven, brazing the repair, and slowly letting the block cool.  Several weeks later I was able to get the block properly repaired.  The brazer was also able to build up the web flanges so that the original stiffness of these webs would be restored. The only drawback was that the oven temperature melted the babbitt material that formed the bearing surface for the crankshaft.  This was known going into the repair, but was necessary in order to properly repair the block.  The plan is to have this babbitt poured and line drilled to the proper diameter for the crankshaft in June.

Model T engine