Saturday, January 28, 2017

Triumph Spitfire Engine Rebuild #9

This is also a rather lengthy post, so thanks for your patience in advance.

Since the motor gets appreciably heavier when the crankshaft gets installed, I wanted to take care of the few things on the back of the motor before I got too far to lift the thing off the stand. Namely, there is an oil gallery plug back there and the core plug for the rear of the camshaft. I couldn't get to either of these adequately, so I pulled the motor off the stand and on to the bench. The two plugs were quickly installed and the motor put back on the stand for crankshaft installation.

Oil gallery plug is the hex-head plug in the middle left of the block. The core plug is that gaping hole you see.

As I've mentioned, the crankshaft has had some work done, machining the main journals down by 0.010" and the crankpin journals down 0.020". To verify that these still checked out, I needed to use an outside micrometer to measure each of them. There are a few ways to approach this. In my study (yes, YouTube videos), I determined that I wanted to measure each journal in four different spots. This would provide enough information to determine if the journals were tapered or out-of-round. The trick here is to establish a point of reference that you want to use. You can mark the crankshaft, use the Woodruff key...anything that makes sense to you just as long as you keep your measurements straight for future reference.

I chose to use the Woodruff key as my point of reference and set it facing me. From here, if I measured the journal with the micrometer parallel with the Woodruff key, I called it the "x" measurement; perpendicular, the "y" measurement. Since I was doing four measurements per journal, there was an x1, x2, y1 and y2. The "1" measurement was towards the front of the journal, as referenced to the crankshaft nut, while the "2" measurement was towards the rear of the journal.

Crankshaft positioned with the Woodruff key facing me.

First, I cleaned the crankshaft and the micrometer with CRC Brakleen to remove any foreign material and oils. Buy this stuff at Walmart...cheapest I've seen it anywhere at about $3.50 a can.

Because I hadn't done it yet, I used a small nylon tube brush to run out the oil passages in the crankshaft...

Each passage goes from the main journal, at an angle, through the crankpin journal. Interesting.
...and then blew compressed air through them for about 10-15 seconds and then a final air blast over the crankshaft. Using my readers (magnified about 1.0X), I looked close with a bright light to make sure I didn't miss anything.

Before I continue, a general word about cleanliness and I won't mention it again. When I had my Midget back in high school, lack of attention to detail on my part caused me to ingest the small nuts that held the air cleaner to the carb body into the engine (I forgot to put the lock washers back on). I cracked a piston or two. I replaced all of the pistons and the connecting rod bearings. I did not pay any real attention to cleanliness during the job and, within about a month, I struggled to maintain oil pressure as the bearings slowly ate themselves due to foreign material damage.

I've learned my lesson. So, at any time I mention installing or removing any bearings, bearing caps, the crankshaft...anything...I cleaned everything with Brakleen and compressed air. I also changed my nitrile gloves several times. While foreign material may throw off measurements, cleanliness is especially important during final assembly. So, as you read, keep the cleanliness chore in the back of your mind at all times.

There are a bunch of YouTube videos out there on how to use and read a micrometer, so I'm not going to repeat that information. However, I had a hard time finding information on how to zero one, so I will cover that.

It is a straightforward process, but important as I'll be measuring to the nearest 0.0001". Granted, my micrometer set is not that high of quality, being from Harbor Freight, but process is process and I wanted it to be as accurate as possible.

With the micrometer set comes two primary standards, one that is 1" and the other that is 2" and an adjusting wrench. Since I was using the 1-2" micrometer, I chose the 1" primary standard and tightened the micrometer on it.

The 1" standard in the micrometer...turns out it was right on in this picture.

If the micrometer does not indicate 1", the adjusting wrench is inserted into a small hole in the sleeve, or barrel, and it is rotated in the appropriate direction to get the micrometer zeroed.

The small hole in the micrometer's sleeve (barrel).

The adjusting wrench inserted to rotate the sleeve counterclockwise. Flip the wrench to go the other way.

After all of that build-up, I got my measurements of the main and crankpin journals. The workshop manual calls for 2.0005" to 2.0010" for the mains and 1.6250" to 1.6255" for the crankpins. With the machining work done, I expected to get 1.9905" to 1.9910" for the mains and 1.6050" to 1.6055" for the crankpins. Turns out, I got the right values in the right spots! Yea, me!

#1 journal x1 measurement.

#1 journal y1 measurement.

For the cute little engine it is, the crankpin journals are not wide enough to get two measurements, so only one was taken and they were just called "x" and "y". Oh, and as a general rule, don't measure near the oil passage holes. This will mess up your results, obviously!

With that information, measuring the bearing oil clearances was next. This is where I made my big mistake that resulted in tearing everything back apart. While I didn't HAVE to do this because I had corroborating information that told me the oil clearances were fine, I'll go through the proper method and then mention what I did wrong afterwards.

To properly measure the main bearing oil clearances, the bearings and main caps are installed in the block and torqued to specification (50-55 ft-lbs) while the crankshaft is left on the bench. Then, a bore gauge measurement is taken to determine the inner diameter of the bearing. The bore gauge reading is, as read, the bearing oil clearance.

First, it's important to get the bearing installed properly. Though difficult to tell with the bearing half in your hand, it is not a perfect half-circle. This becomes very apparent when you push it into its housing and you have to press down pretty good to get it to fit flush. Even then, until the cap is installed and torqued, the bearing is not as round as it will get.

To minimize any offset, it's important to get the bearing centered in its housing as good as you can. The bearing ends will stick up just a bit beyond the housing edge. Use your fingernail to go across the top of housing and bearing end on both side to achieve about the same amount. This is more of a feel thing, but this shows that the bearing is not truly circular - yet.

Hard to see, but the bearing ends just barely stick up above the edges of the housing.

It's also important to get the bearing centered front to back as well. The easiest way I found to do this is to center the tang of the bearing in the recess in the housing that it fits in. I was able to use my fingers to slide the bearing into the appropriate positions, pushing on both ends at the same time so it didn't twist.

The tang and its channel is to the left. This bearing needs to go to the left just a bit. That center channel is the oil channel.

As for the bore gauge, the key here is to zero the bore gauge to the actual crankshaft main journal bearing measurement that you got for each journal. Since mine were practically all the same, I picked the mean value, so the bore gauge was zeroed at about 1.9900". The first time around, I just zeroed the bore gauge at 2", which was the length of the anvil installed. My measurements resulting from this were obviously invalid, but it didn't click why with me until I got home later that night and watched some YouTube to figure out what I did wrong. Doh!


My workshop manual does not explicitly state the required oil clearance, but it does provide the numbers to do the math to figure it out, giving me from 0.0010" to 0.0027". The general rule of thumb that I've been able to find is that the oil bearing clearances run about 0.001" for each 1" of journal diameter. So, since the main is about a 2" diameter, that spec makes sense.

With that done, the main caps came back off.



But, it wasn't quite time to put the crankshaft in for good, yet. Next up was to use Plasti-gage to back up my actual measurements. I got this stuff at Napa for just a few bucks, so it's cheap insurance. It comes in different sizes depending on what you clearance spec is and each size is color-coded. Since I was looking for 0.001" to 0.003"-ish, I used the "green" size, which is for clearances of 0.001" to 0.003". Perfect!

Since the crankshaft had been sitting out unattended for a bit, I blew it down with compressed air (no Brakleen since it hadn't been handled). I cleaned the bearing surfaces with Brakleen and compressed air, and set the crankshaft in. I then used a pair of scissors to cut the Plastigage to the approximate length of the journal and set it in place.

And there it is.

After that, it was time to install all the caps again and get them torqued down.

Installed and squeezing some Plastigage.

I waited a few minutes, then took it all back apart to see how much the Plastigage compressed.

Squished! The skinny part in the middle is where the oil channel in the bearing is so no compression there.

The package that the Plastigage comes in also serves as the measuring tool, standard on one side and metric on the other. It's just a comparator, really, so you hold the paper against the squished part and find what comes close to determine your approximate clearance.

#1 journal looks to be just under 0.002".

A better closeup, except for the glare. Close to #1 bearing.

All of the Plastigage measurements came in very close to each other and they all backed up the bore gauge measurement. So, if nothing else, I have peace of mind. I may screw up a bore gauge measurement, but it's hard to mess up Plastigage.

Now, of course, I had to clean up the Plastigage from the journals and the bearings so everything came back apart again and cleaned as previously mentioned. Since this was final assembly, I applied Permatex Ultra Slick Engine Assembly Lube to all of the moving parts.

Yes, it's red. Even applying it liberally, I doubt I will use more than half a bottle.

This stuff is a very slick and very sticky oil that stays adhered to all of the moving parts during and after assembly. It provides lubrication for the engine's initial start. With a freshly rebuilt motor, all of the wear surfaces are new and dry. With the first few seconds of engine operation providing little to no oil flow/pressure, this stuff helps to prevent damage. Regular motor oil can be used if there is little time between engine assembly and the first start. Given that I have no idea how long it will be until I'm ready to unleash this beast, the stickiness of this stuff will prevent it from flowing away into the oil pan. I'll use this stuff through-out the entire assembly for all moving surfaces.

On the bearing. I put more on than this. You can see the strand between my finger and the bearing. The strand just sat there, not breaking.

With the crankshaft installed, it was time to measure its end float. Two more bearing surfaces that I haven't mentioned are the front and rear thrust bearings, or thrust washers as they are commonly referred to. For the Spitfire, these are half-circle bearings that sit in recesses in the rear main bearing cap.

The thrust washers. The grooves are oil passages.

While the main and crankpin bearings' purpose is obvious, the thrust washers' purpose may not be. The main bearings absorb the vertical forces of the crankshaft as it rotates about its axis and the thrust bearings absorb the horizontal movement of the crankshaft. While some does exists during normal operation, a typical combustion engine does not experience a lot of horizontal force to the crankshaft since the explosions in the cylinders push the pistons up and down, not back and forth. However, when the clutch is depressed, this pushes on the flywheel which, being bolted to the crankshaft, causes the crankshaft to move forward (horizontally). The thrust washers counteract these forces, keeping the crankshaft properly positioned in the block.

By design, the Spitfire's (and other Triumph motor's) thrust washers are not captured to the bearing surface. Over time, excessive wear can result in the thrust washer becoming so worn that it can drop out of its recess in the bearing cap and fall to the oil pan. When this happens, the crankshaft and bearing cap come in intimate contact and they begin to eat each other. Eventually, there is so much horizontal movement of the crankshaft that the starter pinion comes into continual contact with the flywheel gear ring and further damage occurs. There's more to this discussion, but that's the gist of it. You can find out more information at the Custom Thrust Washers website. And, yes, I purchased a set of their thrust washers!

With the thrust washers installed, a dial micrometer and magnetic base is positioned as shown in the workshop manual to measure end float. Using a flat head screwdriver between the crankshaft and #2 main bearing cap, I moved the crankshaft all the way to the rear of the motor. I set up the dial micrometer as shown below and zeroed it out.

Just a bit more zero adjustment required.

With the micrometer zeroed, I used the screwdriver to move the crankshaft to the forward part of the motor. The needle deflected about 0.075", which is within the specification of 0.004" to 0.008" preferred called out in the workshop manual.



At the time that I took these pictures, the old thrust washers were installed. I hadn't done a lot of research on them and hadn't ordered new ones. My research led me to learn all of the unique things about the Triumph thrust washers that I mentioned above, so I went ahead and ordered a set from Custom Thrust Washers. I expect them either Monday or Tuesday. It is possible to replace the thrust washers with the crankshaft installed by just removing the rear main cap. I've already done a video on how to do this.

There are also several other things that I have done to the engine that I'm not covering here, but in the interest of not running for another several paragraphs, I'm going to end the post. I'll get everything else written up and videos uploaded over the next week or so and hopefully get my posts caught up with reality.

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