Building the perfect 90

LRNAD90

Well-known member
All I want for christmas is the next installment of this build thread :ROFLMAO: Pretty please.
It is addictive. So many in the community just blow me away, this is another fine example. Not only do I not possess the skills and patience you do, I have no idea where you find the time between working (have to assume as this is pretty expensive) and Family (with two kids no less!).. Reminds me how much I suck..
 
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erover82

Well-known member
It is addictive. So many in the community just blow me away, this is another fine example. Not only do I not possess the skills and patience you do, I have no idea where you find the time between working (have to assume as this is pretty expensive) and Family (with two kids no less!).. Reminds me how much I suck..

Several updates coming soon. Progress is made with late nights, work breaks, weekends, and testing marital patience. If possible I occasionally either involve the kids or let them run around the shop while I work. I keep the most dangerous chemicals and tools out of reach and they have their own kid workbench, tools, and RC cars to play with. When having kids forced me to eliminate nearly all my hobbies, my remaining resources were focused into this one endeavor. It's a really hard thing to balance but persistence will win!
 

erover82

Well-known member
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Out of curiosity, I looked up the old registration plate and found a few interesting bits.
  1. The vehicle mileage was much higher than stated upon import. I'm guessing the speedo was swapped at some point.
  2. It failed 36% of its 14 MOT inspections.

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erover82

Well-known member
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The new and freshly painted chassis remained in the warehouse, curing and then gathering a considerable amount of dust while the search for a good D1 rear axle commenced. Meanwhile, back in the shop I pressed on with whatever tasks I could find to chip away at.


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The old chassis was further stripped down, leaving only the components necessary to roll it out of the shop and onto a dolly. From there it was towed to a local member's farm where it waits to possibly see another day.


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The rear tub was partially broken down and I spent a lot of time pondering and researching what strategy to take with rebuilding it. More on that later..

The shop was a mess after this flurry of disassembly. Dozens of components littered the floor in various states of filth and condition. Much time was spent trying to make sense of it all. However, one particular assembly would demand more attention than all the others by far.

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The engine sat on a pallet looking rather sad, and as it did it began to speak in soft tones.

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Being that the engine ran strong and sounded healthy, and having already bit off more than might be wise for a family man, I hadn't planned on doing much with the it other than replacing seals and cleaning it up. Nonetheless, like the sirens of a shipfitter's Odyssey, it beckoned in an alluring low call "rebuild meeee". The tethering ropes to sanity could never hold.
 
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erover82

Well-known member
She may have sung a sweet song, but in reality was merely a filthy rusty lump.

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On the stand it went and the teardown began, because what I really needed at this point was more parts strewn about.
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Intake, exhaust, and turbo removed.


Making gaskets and steel blank-off plates.
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Getting further along now. Another plate was made to blank-off the intake and exhaust ports.
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Sealing off the internals in preparation for the next phase. In retrospect I might have simply removed the shafts and internals first.
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Outside it went; sealed, plugged, and blanked as best possible before being blathered with oven cleaner. After giving it time to melt the many years of grime away I blasted it with a heated pressure washer. Next up was aircraft remover and not the new skinny-pants compatible, spotted-owl friendly, methylene chloride free kind. No, the kind that given the chance would melt the hide off a rhino. In fact, my old can of it had been sitting long enough that it ate a hole through the side in an attempt to escape but then dried fast enough to plug its own escape route.

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erover82

Well-known member
The power of methylene chloride stripper is well illustrated in the close-up below. Paint falls off like the meat off a rib rack. The block had long lost its factory gold coating and had been indiscriminately painted silver at some point afterward, but that too succumbed to the power of chemistry.

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Now with it fully stripped and mostly dried I began taking stock of what would need to be done. Noticing the many details that would be necessary to address in order to return it to factory-like glory, that sinking feeling of being overwhelmed returned.

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Fully dried and flash-rusted, but clean and workable now. That rusty sump cover would be a project on its own.

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Tearing into it. This engine had been rebuilt before, as evidenced by the crank being marked as ground .010" over and the block itself stamped 020. The bearings looked good with only a few small spots of copper showing, but the crank journals were lightly scored so would need polishing.

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The crankshaft nose would need dealt with as well. A previous owner had "repaired" the worn slip fit of the torsional vibration dampener by shimming it with strips of sheet metal. In particular sections the wobble eventually lead to the nose being eaten as much as .010" across the diameter.

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Head, piston, valves, and cam out. Let's see what we find.

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The rocker assembly looked quite good with exception of this one unfortunate rocker. These findings reaffirmed my decision to dive in.

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It was time for the major components to ship off to a machine shop, but the shop I had last used was too busy to take on new jobs. The next four shops I contacted had the same response or didn't exactly impress much confidence. After some more calls I settled on a shop in a nearby city. We had a conversation about the work in which they had expressed the willingness, a helpful tone, and the ability to have the work done in a week or so.

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Ten weeks dragged on before I saw my engine again.
 

erover82

Well-known member
Ten weeks dragged on before I saw my engine again.

What began as checking in every few days with the machine shop, slowed to weekly checks and then bi-weekly as the pandemic, work, and family life distracted my focus. As before, I'd also taken up several other necessary rebuild tasks to fill the time and make progress towards the larger goal. Here are a few.

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With the major components off at the machine shop, I focused on what remained. The injectors were on the bench and would eventually need attending to, so why not now?

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Into the ultrasonic they went.

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..then wire-wheeled. Looking much cleaner. How to finish them though?

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The decision was made to blue them, like a rifle barrel, and so I did.


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Pleased with the results, I placed them in a box and labeled them as prepped for reassembly.


The sump pan.

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If you'll remember from earlier, it was looking a bit rusty, but that was just the outside.


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Once drained and looking at the inside, I first noticed this 1/4" chunk of aluminum. Where had it come from?

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After some sleuthing I found its origin at the bottom of the block ladder frame. One of the blind threaded holes had been pushed out when someone fastened the bolt down with RTV trapped at the end. The hydraulic pressure escaped through the path of least resistance. Fortunately it's inconsequential as a dab of thread sealant will prevent any leaks upon reassembly.

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Further examination revealed that a plate had been welded (poorly) to the bottom, the source of several leaks. I spent about a week repeatedly redoing all the welds and grinding them down to smooth radiused corners that would restore a factory appearance. I had decided to keep the added plate, for it added strength and appeared to be the slightly less laborious path to take. However, this complicated welding as a layer of oil was trapped between the factory bottom sheet metal and the added plate. This resulted in repeated battles with weld contamination, but I eventually was able to overcome it with angle grinder, die grinder, and welding persistence.
 

erover82

Well-known member
Sump pan continued..

Here we see the surface rust being removed via wire wheel. The deeper pits were carefully welded and ground smooth. The remaining pitting was judged as being cosmetic and would eventually be filled with a strong epoxy.

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I wish I had taken more photos between this stage and painting, but after all metal work was done I blasted it with coal slag and immediately coated it with the first layer of SPI black epoxy. Over several more days I sanded and sprayed epoxy five additional times before finishing it off with a final two coats of semi-gloss engine enamel.

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This was before the final even gloss had been achieved after curing and de-nibbing, but I was pleased with the result and it sure beat spending nearly $700 on a new pan.

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Bonus shots of it curing in the make-shift oven.
 
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erover82

Well-known member
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Pleased with the results, I placed them in a box and labeled them as prepped for reassembly.

I had the best intentions with these, but in the back of my mind, I suspected cold bluing might not be adequate for the long term. Combined with an annual anti-corrosion coating like CorrosionX they'd fare well, but that's not a maintenance item I'd like to introduce. This suspicion was confirmed when I pulled them from the box I'd stored them in, only to find spots of surface rust already setting in. Time to invest even more hours in them!

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I also decided this was an opportunity to rebuild them with new genuine Bosch nozzles.

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If not blued, how about Cerakoted? I had some extra Piston Coat which would be very durable and in a color that would mesh well with the rest of the engine.

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Each one sanded, degreased, and Cerakoted.

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Internally these are comprised of a series of fiddly little springs, rods, and spacers, which despite my effort to remain organized, became mixed up. It took at least an hour of carefully examining minute wear patterns with a magnifying glass to determine where the estranged parts belonged.

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Complete.


..or not. I knew I should have media blasted them instead of sanding, so of course adhesion was not adequate and it wasn't long before the coating started chipping off. I knew better than to be lazy with paint prep. Round three with these things will be blasting them with aluminum oxide and re-Cerakoting. Lesson learned.
 

erover82

Well-known member
Continuing the disassembly, cleaning, restoring, and coating theme - here are several more parts that were processed before the rebuild began.

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This thermostat housing was badly corroded at both hose connections.

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Heated the housing with a torch and was able to remove the rusted hose barb. I struggled to find a suitable replacement but eventually found one with nearly the ideal dimensions. Had I owned the hydraulic pipe flaring tool I later purchased, I might have just made one.

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The new fitting was actually a few thou too big for a proper interference fit, so I reamed the hole to the proper diameter.

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The fitting was a bit short after curing off the threaded portion. I wanted a spacer that wouldn't rust and would help it seal when it was fitted and bottomed out in the hole.

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Took a few brass washers a machined them down to fit.

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Correct height now. Will it fit?

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Just right.

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Heated the housing again and pressed the fitting in.

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Next up was the cast hose connector which was also corroded. To remedy this I mixed up some metal epoxy and applied it to all pitted areas.

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The epoxy was then sanded down before the entire housing was polished. I later chose to paint this and the other cast aluminum parts for uniformity and added corrosion protection.
 

erover82

Well-known member
More parts refinishing

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Wire-wheeled and cold blued the timing pulleys

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Prepping the air-filter canister knob for paint

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Yet more parts disassembly

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All parts were then media blasted with coal slag or aluminum oxide. They then received two coats of epoxy primer and two coats of semi-gloss engine enamel paint. This was done in batches as there were a lot of parts to manage. For example, parts will begin to surface rust after media blasting if they're left too long before priming. Also, paint and primers have specific mixture, temperature, humidity, and timing specifications that need to be adhered to for best results.

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Most parts were sanded between primer coats for best results, or because life had intervened and I'd passed the time window for top coating without sanding.

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Back in the paint tent again for top coating.

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Much of this was done at night in the freezing cold while struggling to heat the tent to the required temperature for the coatings. These were stressful times trying to make sure everything went to plan, which it often barely did.
 

erover82

Well-known member
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This batch of aluminum parts had also been media blasted but with fine grain aluminum oxide and coated with gray epoxy primer.

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They were then top coated with "cast aluminum" colored engine enamel.

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The front cover housing was damaged where the power steering bracket mounts. The broken section with missing material was TIG welded up and then re-tapped. The stripped thread above was repaired with an insert.

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It too was then refinished with the same strategy as previous aluminum parts.

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A batch of fully finished parts.
 

erover82

Well-known member
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Moving on to the pistons, the graphite coating on the skirts had worn thin, and even more so after going through the parts washer.

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Masked off and ready for media blasting with fine aluminum oxide. To restore the skirts I selected Cerakote Micro Slick, which is a low-friction and oil-shedding coating similar to the factory graphite coating.

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It took several coats to achieve the build I was looking for. Using the turntable above for both blasting and coating helped achieve uniformity. I declined to coat the combustion area with a thermal barrier coating after reading research conducted on similar engines that demonstrated moderate emissions and minimal power benefits.


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The rods were freshly resized and bead-blasted at the machine shop, and I had some leftover Microslick so I decided to coat them as well for the oil-shedding properties.

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Freshly coated

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Unfortunately, the machine shop that did the rods didn't think it necessary to mask off the small-end bushings. They assured me the bead blasting would have no ill effect on them. I disagreed and didn't bother masking them off for coating either, knowing I'd have to replace them.

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New bushings pressed in and reamed to match a set of new gudgeon pins.
 

Tbaumer

Technical Excellence Contributor
Super impressed with the knowledge & fearlessness to tackle every part of this build yourself. Really appreciate lots of quality pics & explanations, as I’ll be looking back on this thread when I get the nerve (& time) to rebuild mine.
 

erover82

Well-known member
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Over all this time restoring parts I had been separating out those that were originally zinc plated but had seen better days.

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These were painstakingly wire wheeled by hand, vibratory tumbled, ultrasonic cleaned, and/or media blasted to get every last bit of oil, dirt, and corrosion removed.

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These parts were brand new but merely black oxide coated or just bare steel, both of which would quickly corrode. They were wire wheeled and included in the lot.

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I noticed previously that the steel components of these fuel caps corrode very quickly, so they too were disassembled and thrown in.

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Ready to ship off for plating. The yellow bit is a plastic VCI tab to prevent corrosion of the vulnerable bare steel in shipping.





3 weeks later..


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Freshly zinc plated and yellow passivated. A satisfying package to open.
 
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erover82

Well-known member

Last we saw the block, it was degreased, paint stripped, and torn down, but rusty.


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Masked all openings and gasket surfaces off with 20 mil PVC tape. All threaded holes blocked with silicone plugs. This took a few days to get just right.


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After media blasting with coal slag it quickly received its first coating of light gray epoxy primer. To prevent flash rust, no time was wasted between blasting and primer, and consequently no photo after being freshly blasted. Also, the longer it remained outside, the higher the chance of some bird landing a flying air shit on it.


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After four coats of "aluminum" engine enamel. I know these blocks were gold from the factory, but I prefer this.


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After an initial 24 hours I added a heat lamp to cure the enamel from the inside-out. I later added a second heat lamp for higher temps and more even coverage.


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Pulled the core plugs and of course they were rusty.

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Peeking inside the block revealed an expected amount of rust flake sediment. If you'll recall, this engine was run apparently without antfreeze so the entire cooling system had suffered some corrosion. However, looking at the internal cooling passages, the Thermocure flush I'd performed appeared to have done its job. I spent a good amount of time blowing the entire system out with compressed air until it was fully clear.

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All new core plugs in place. Also, testing showed the epoxy and enamel had fully cured to a hard finish with strong adhesion.
 
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jymmiejamz

Founding Member
Callsign: KN4JHI
View attachment 23729
Over all this time restoring parts I had been separating out those that were originally zinc plated but had seen better days.

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These were painstakingly wire wheeled by hand, vibratory tumbled, ultrasonic cleaned, and/or media blasted to get every last bit of oil, dirt, and corrosion removed.

View attachment 23730
These parts were brand new but merely black oxide coated or just bare steel, both of which would quickly corrode. They were wire wheeled and included in the lot.

View attachment 23733View attachment 23734
I noticed previously that the steel components of these fuel caps corrode very quickly, so they too were disassembled and thrown in.

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Ready to ship off for plating. The yellow bit is a plastic VCI tab to prevent corrosion of the vulnerable bare steel in shipping.





3 weeks later..


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Freshly zinc plated and yellow passivated. A satisfying package to open.
Looks great. Why did you choose zinc over cadmium?
 

erover82

Well-known member
Looks great. Why did you choose zinc over cadmium?

I would have had to ship the parts much farther to reach a plating company that does Cadmium. It's less common today due to its toxicity. The other factor is that Oregon hasn't really invented rust yet, so it should last a very long time.
 

erover82

Well-known member
The crankshaft nose would need dealt with as well. A previous owner had "repaired" the worn slip fit of the torsional vibration dampener by shimming it with strips of sheet metal. In particular sections the wobble eventually lead to the nose being eaten as much as .010" across the diameter.
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I struggled deciding what to do with this crankshaft. The journals only needed a polish but the nose had the aforementioned wear to deal with. I could get a new one from Turner but at a not insignificant expense and it seemed wasteful to toss an otherwise good major component. After discussing it with several machinists and weighing the options, I decided to try and repair it myself.

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I started by having the the journals polished and then moved on to mounting it with new King bearings.


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End float just right.


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Mounted and ready to start the repair, I first removed any surface rust with Evaporust.


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Then cleaned thoroughly and sanded.

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Grinding a washer to the exact ID and OD that the crankshaft should be.

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Using the sized washer and a section of an old straight edge to view the areas that needed built up. The worst of it amounted to only 10 thou where the torsional vibration dampener sits.

I could have simply used sleeve retainer, but that would make any future disassembly challenging.

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Metal epoxy! The idea was to use it to build up the material just enough to achieve a perfect slip fit of the timing gear and TVD.

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Lots of sanding, checking with washer and straight edge, and applying more epoxy.
 
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