02 The Great 2020 Miami Caper

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Amskeptic
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02 The Great 2020 Miami Caper

Post by Amskeptic » Sun Apr 19, 2020 6:16 pm

( prior installment 01: viewtopic.php?f=79&t=14002#p234777 )
Made it to Miami by the evening of January 5th, and exoticdvm, Jivermo, and I launched into a discussion of our engine rebuild, our hopes, our rules, our logistics, our "plans". We needed to disassemble the engine carefully. The clues as to why the engine made weird noises and had low compression would present themselves to us ... but we had to catch them during the disassembly!

Engine was out by 10:30am or so:

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Do you see any sort of ... trepidation ... on Marc's face? I do. These guys of BirdingByBus fame had been through the wringer over the past few years. Their complete engine overhaul of just 15,000 miles had bedeviled them with odd noises emanating from the engine all the way since last year when we met up at this very spot. At some point in their epic journey to Alaska in 2018 to get married and birdwatch, the engine had gone off-song and had failed so exquisitely perfectly that it did NOT grenade when the valve seat let go in Calgary CN. After a few thousand dollars of emergency head replacement surgery, they still had some issues with low compression. I promised them that this would be the last damn stop for them, that we would be focused only on correct procedures and replacing all necessary parts as necessary but not if unnecessary! Well, here's a little clue:

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Turned out to be a screwdriver lodged under the right upper cylinder tin, partially melted onto the cooling fins to the #1 exhaust port area:

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We continued to methodically disassemble the engine (low compression! weird noises!):

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Did not take much in the way of forensic sleuthing to see that we had a bit of a leak at #1#2 head:

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But why? That is the question. There were no signs of overheating that would cause the clamping to relax. There were no head sealing rings to fail (though they are just canaries in the Loose Cylinder Head Coal Mine). No, what we found was that the Calgary shop had used RTV sealant on all of the head studs. RTV is not to be confused with Permatex Aviation or Curil or any of the other acceptable sealants. RTV sets up relatively quickly, and it causes friction as the nuts are torqued. We determined that the specified torque of 23 ft/lbs was likely met at the torque wrench, but it only had about 15 actual foot pounds of clamping at the head. Once combustion gases escape, the problem only gets worse as gas erosion begins to upset the machined sealing surfaces.

We tested the valves to see if they had in any way contributed to the low compression. Our gasoline steep test showed the valves were fine:

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This shot shows the impending stress of having a lot of parts coming off the engine. We bagged them in some semblance of "order" with labelled slide-loc bags, but an engine overhaul develops a lot of mental notes regardless:

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Judgment calls came up. Here we are. Do we need pistons and cylinders? (When I went to Atlanta to get the new Len Hoffman heads, I did throw the new set of BobD German pistons and cylinders in the trunk of the Lexus, just in case ... ) We decided that we sure did need new pistons and cylinders! Look at the scoring on #2 here. look at the oil wet pistons! Yeah, plus we saw a little moon crescent on the #2 piston from the Calgary dropped-seat fiasco.
( how close did the engine get to big trouble in Calgary? Real close )

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A little bit of hesitancy as I offered up the German Kolbenschmidt pistons and cylinders, and Marc hit his cell phone and got an overnight order of Mahle pistons and cylinders from the Bus Depot!
Into the engine we went (low compression checked off, but weird noises still yet to be determined). Lifters actually passed the test and were carefully organized in the kustom McIntyre Lifter Container:

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Weird rattling noises at idle ... what could cause that? Parts that accelerate and decelerate noticeably at idle! What parts accelerate and decelerate noticeably at idle? Camshaft. Camshaft gear. Oil pump drive dogs. We pored over the engine without disturbing a thing. Gently wiggled the camshaft while it was still in its 15,000 mile mesh with the crankshaft. Well hell. The gear mesh wasn't bad, but the camshaft itself walked back and forth in the case. .013" end play, in fact. The crank was no better! .012" (wear limit is .006") Then I saw chew marks on the camshaft gear. Four sets of them. And you know what causes that. Somebody had pulled the crankshaft gear off at the last rebuild with a puller that had *bent the teeth*. Since the crank gear rotates twice for every camshaft rotation, those two bent teeth spots were "printing" on the camshaft gear in four discrete spots:

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Pulled the camshaft off after this diagnostic moment, and discovered another diagnostic moment. The cam bearings were all wiped oddly shiny on one side of the engine. Discovered a cam bearing that had not been installed correctly at the last overhaul. The little tang that is supposed to fit in the little tang slot in the case had missed by a good 1mm. This meant that the bearing was not fully pressed into the case and that made the camshaft ride hard in the opposite side bearings:

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Thus we had low compression and funny noises pretty well scoped out. Eliana jumped into Executive Mode and began the enormous and unenviable task of making sure that all ancilliary parts were cleaned and prepared for painting.

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I finished disassembling the case and pulling the connecting rods (and checked their bearing clearances! .002" plastigage) so I could take it and the crankshaft to some "Elite Machining" shop for a cold tank and a proper crankshaft gear pull (no more bending teeth!).
"Hey, can I drop off a crankcase for a cleaning and could you pull a crank gear, oh and stick in some new rod bushings?
"Sure! We'll have it done next Tuesday."
"I'm sorry, can we have it by tomorrow afternoon?"

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And so it came to pass ... Elite Machining took pity upon my piteous and novel story "um, we're in a rush," and grumpily suggested that I call to see if the new rod bushings might make it in "tomorrow by noon," and I dropped the parts off at the front door. Made it back in time to carefully carefully measure the crankshaft across all thrust axes and compare to the TDC/BDC axes for out-of-round and wear. We were pretty close to the wear limit on the thrust bearing saddle, but I had a trick for that. Camshaft spewed a bunch a numbers that we eventually decided were "good", and I set to filing the crank gear bent teeth and the camshaft gear chew marks smooth once more. Hey, see the push rods? Don't let them get mixed up either ... :

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Next day, I gathered up the parts from the now-expansive Joe at Elite Machining, "hey if you need anything, call!"
Poor Joe. I did. I called. In hours. The new wrist pin bushings were reamed too loose. You cannot use bushings that allow the wrist pins to click. That is too much play! Slide fit only!

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Joe was less expansive now. "Well, I don't think I can get another set of bushings that fast."
"I'll bring them right down, Joe. Thanks so much! What a rush, huh?" And I got back to start razor-blading the case halves in all the places I love to razor blade case halves, the saddle edges, the seal edges, the ... #1 main bearing saddle mating surfaces to make the hole a little smaller when the case is bolted up (don't tell ANYone) ... :

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January 9th, got some snug wrist pin bushings back from Joe at Elite Machining. Well, thanks, Joe, the speedy service was truly appreciated. But oops, man, ya forgot to drill out the oil holes in the new bushings! Good thing we're on this stuff, huh? A neophyte would have proudly assembled his/her new engine with care and wondered why the engine got squeaky and broke a piston skirt ....

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So here we are, we have a mostly fully disassembled engine, you can see parts all clean-looking surrounding the crankcase, that is because we have a full complement of souls on-board here, all working diligently out and around the barn, filing and sanding and scrubbing tins and pipes and fans and housings and trying not to step on plastic bags ... there is a piece of paper taped to the wall sort-of, with critical numbers off bearings and end play readings so we can figure out how much to substitute thicker shims if and as necessary with the new bearings which we ordered pretty much on faith that we had measured correctly. Yeesh.

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Now things get interestinger ....
(next installment 03: viewtopic.php?f=79&t=14007#p234806 )
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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Amskeptic
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Re: 02 The Great 2020 Miami Caper

Post by Amskeptic » Tue May 26, 2020 1:39 pm

( place holder )
BobD - 78 Bus . . . 112,730 miles
Chloe - 70 bus . . . 217,593 miles
Naranja - 77 Westy . . . 142,970 miles
Pluck - 1973 Squareback . . . . . . 55,600 miles
Alexus - 91 Lexus LS400 . . . 96,675 miles

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