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Sherlock9C1 builds a wagon

12974 Views 144 Replies 16 Participants Last post by  MWP
[editor's note, I'm migrating this over from GMLongRoof forum, so some of this may be repetitive from my Impala build thread]

Hey guys, it's about time I posted up my wagon project. I've owned B-bodies since 2003, but in late 2013 my fourth Roadmaster wagon sadly caught fire a week after I bought it and was a total loss. I had just moved 1000 miles south and with a new job, three young kids and a whole new city, I needed to simplify. So I sold all three of my B-bodies and just drove minivans for 5 years.

My dad suddenly passed away in fall 2017 and the next summer I ended up inheriting his '96 Impala SS (Dark Cherry, the car I always wanted). It was drivable but needed a lot of work. I was going to sell it, but shortly after I got it to my house the buyer flaked out, so I just drove it and remembered why these cars are so fun (especially compared to minivans!). My wife and I decided to sell one minivan and make the SS my daily driver (which you can do in the Southern US), so I started disassembling it to restore. (That build is over here).

Four months later, while looking for parts, I located a 96 Roadmaster wagon project about 2 hours north of me. The owner had started to build it but hit some snags and health problems and it had been sitting partially disassembled for two years. I figured SURELY he'd be willing to sell some parts from his stash, but no, he said he wanted to sell the whole thing together, and he made me an extremely compelling offer. So I did what any self-respecting guy would do, I told him I'd talk to my wife and call him back.

We talked it over and decided to go ahead and take a good hard look at the wagon. It was dirty and neglected, but other than a hellacious battery acid leak and an unfortunate rainwater accumulation in the left rear quarter, it was rust free and in very good condition.

So we loaded it up with parts, loaded my minivan full of parts, strapped down the powdercoated rear axle and the 383 he had acquired for it (on a specially designed radial transport fixture) and he trailered it to my house.

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Amazingly the plasigage is still pliable.
Time flys , I bought the inside- outside mics in 1973!!


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Side note, I purchased the Melling Shark Tooth oil pump for this engine. The gears are twisted, like a Whipple supercharger, for much-reduced oil and torque pulsations. It was $60 more than a regular style oil pump.
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I'll deburr the sharp edges inside and it'll be good to go. Speaking of de-'burring', even as we were taking it apart and inspecting it, a burr came off. Byebye sharp edges.
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A dear friend who knows his way around engines and vehicles came over and helped me check the top ring end gaps. I wrote them all down; they were all around 0.022-0.025 with one at 0.029 on cylinder 5.
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Here's a trick to square the rings before measuring - take a piston and just push the rings down into the bore util it rests on the oil ring.
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We assembled several rod bearings with the stock shells to check clearance. These shells were -0.001" undersize (tighter than stock), with severe wear on the upper shells. This one was definitely under 0.002" clearance.
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Here's one on the #4 journal:
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Same one; less than 0.0015." This was with the crazy wear shown earlier. Bearings were dry while tested.
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Interesting marks on the rod cap insides. I also found it interesting that there was oil behind them when I pulled the shells out. They are supposed to be assembled bone dry and tight for heat transfer and proper crush/anchoring to prevent spinning.
Hand Wheel Automotive tire Tire Bicycle part

Bottom line, the 0.001" undersize bearings were suitable for the mains but NOT for the rods. I'll most likely end up going X bearings (0.001" oversize) on the rod bearings. Following 95wagon's suggestion, I'm going to purchase a dial bore gauge to get more accurate readings.
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It might be the lighting , those journals look awfully rough finish.

To restate, while a bore gauge is nice it is a luxury.
Properly used , quality inside - outside mics will show you .00025 easy and you can eyeball closer than that.
The graduations are .001 but you can read between the lines, so to speak.

To each their own but I will always use a coated bearing if available.
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@95wagon definitely lighting, but I think I am going to have the crankshaft polished. The mains had some scoring I'd like to knock down.

Part of the challenge is that the Starrett outside micrometers I have are very old and they don't have the vernier marks on them, so it's all eyballing between thousandths. 0.00025 is probably doable.
Mine do not have graduations between the .001's but seeing 1/2 - 1/4 of the thou pretty easy , 1/10th do able.
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they were all around 0.022-0.025 with one at 0.029 on cylinder 5.
One hole big ?

Time for file fits ?
Does ring gap really matter that much once you get above 1000rpm? At 1000rpm, the piston goes from bottom to top in 31ms. At 2000 rpm, that number drops to 15ms, and so on. Not much time for mixture to leak past the first ring, go around the piston to the second ring, then past the oil rings.
Biggest issue I've seen is the gap being to small and allowing the ring ends to contact one another.
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Does ring gap really matter that much once you get above 1000RpM?
At 1000RpM, the piston goes from bottom to top in 31ms.
At 2000RpM, that number drops to 15ms, and so on.
Not much time for mixture to leak past the first ring, go around the piston to the second ring, then past the oil rings.
It must matter somewhat, because (my understanding is) letting ring gaps line up is a known faux pas.
How much it matters, I've no clue, except I'll guess that, as little as it could be, it must be cumulative.
i remember getting paranoid about messing up on staggering the ring gaps on an engine i built. tore it down a year later and the gaps were all over the place.

cool thread sherlock!
Some interesting articles on bearing clearances for your enlightenment:
  • From Mahle.
  • Older Motor Trend with Callies data on clearances versus oil flow/loss, temperature rise, and load capacity.
  • 2019 from Motor Trend with some discussion of hydrodynamic wedge.
  • 2007 from Engine Masters Challenge.
  • Some good tricks from Jeff Smith in 2008 about fine tuning clearances with different bearing sizes.
  • Engine Labs 2016 discussion of clearance relative to oil weight.
Another update on the wagon engine build. Nothing like telling your car buddies you're having an engine build party to force you to get the workshop cleaned and get everything in order.

Time for final installation of the crankshaft. Since I plan on running a standard volume oil pump with 5w30 oil, I kept the main bearing clearances at .002". This will be a non-nitrous street motor and the shift points will be at 6000rpm or below. This is believed to be an old COLA crank; the mains were a bit on the small side so I used 0.001" undersized on 1-4 and a STD size on #5.

Note that we started at #3 and tightened them one at a time so we could check for binding. I list them in order here though.

#1 journal; just over 0.002".
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#2. Right at 0.002 if not a hair under. These Clevite P-series bearings will discolor if you look at them funny.
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#3. just a hair under 0.002." The photo makes it look tighter than it was.
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#4. Right at 0.002." I know these pictures haven't been great at lining the edges up; parallax ends up being significant in these plastigage photos for some reason.
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#5. Just slightly above 0.002". From lots of reading, you want the #5 journal to have a half-thou extra clearance to allow sufficient oil to reach the thrust surfaces on this bearing. So it's good.
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After we installed #5, the crankshaft was binding about halfway around. This is a dead giveaway that the thrust bearing halves are misaligned.

We set up a dial indicator and got absolutely no end play. That's no good.
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So we removed the rear cap and got 0.0045." The crankshaft spun freely too. Yep, definitely a #5 cap misalignment (front to back). Factory LT1 spec is 0.002-0.008." Then we put the cap on and spent an hour shifting it around and could only get 0.003". After a lot of head scratching, we measured the thickness of the other rear bearings and they were all 1.716" thick, so we didn't have a bum bearing. Then we looked at the rear cap and found a burr (it's under the guru's thumb, but you get the idea).
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So we deburred it and then got our extra thou and a half back. 0.0045" end play, right in the middle of spec. It's worth noting that the old bearing had zero wear on the thrust surfaces so it hasn't been an issue in this motor to date. The crankshaft spun freely and uniformly so we were good.
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We were going to install all the pistons but it turns out I hadn't actually ordered the X (oversize) bearings yet. Woops. STD bearings were at 0.0015" on this crankshaft, so that's a no-go. We installed one for deck height and piston rock measurement.

The guru lost much of his engine building tools in a divorce, but still had this nifty tool.
Automotive tire Engineering Gas Metalworking Machine

After some playing around, we concluded that the pistons are at zero deck. Piston rock side to side total is .0185", and piston rock along the wrist pin (with basically no oil in it after cleaning) was 0.005". So basically the piston could come up out of the bore as much as .00925." I was tempted to run a thinner head gasket than the FelPro 1074 (0.039") but I'll wait to see what the piston to valve clearances and cylinder head CCs measure at before a final decision. Just running the numbers right now, with 55cc combustion chambers, a -14.9cc dish and zero deck, I'm at 11.6:1 compression. Pretty steep for a street motor. I'm planning to radius the sharp edges on the heads and run colder plugs to see if I can avoid 93 octane along with conservative ignition timing.
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the reverse cooling will help here along with cam selection and some spark map tuning. don't get to hung up on compression and pump gas too much, quench is more important IMO. i ran mid grade (89) all summer in my 10.3:1 350 with iron "door stop" TBI heads. the Internet will say compression is bad but it makes the engine more efficient. my engine made the most power @ 26* all in timing on the dyno. made about 20ft/lbs and 15hp LESS @ 32*. even the dyno operator was surprised.

btw my quench is in the .032" to .035" range.
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So, after we put the crankshaft in, I became concerned that the workshop had been cold prior to assembly, and a small space heater warmed up the shop only 5 hours before assembly, and the crank had been left 6" off the ground while the block was on an engine stand the whole time, and I'm intentionally not swirling the air around to avoid stirring up dust. Plus, knowing that all the mains had been assembled using 0.001 tighter bearings, I decided to go back and change the upper shells on journals 2, 3, and 4 to STD bearings, and run a complete STD bearing set on #5. FYI the thrust bearing is spec'd by GM for looser clearances to allow more oil to leak out to lubricate the thrust surfaces.

So, the bearing shells are, by upper/lower:
  1. -1/-1
  2. 0/-1
  3. 0/-1
  4. 0/-1
  5. 0/0
Karl Ellwein uses a similar scheme when assembling his blocks so I took a picture of mine:
Product Automotive tire Gas Automotive exterior Auto part

One rule if you're building an engine: one can never have too much plastigage. It's cheap, buy plenty of it.
I carefully laid in the crankshaft and plastigaged all five journals one more time.

#1: Right on 0.002"
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#2 - right on 0.002". The picture makes the plastigage look wider; this iPhone camera does NOT like taking pictures of plastigage.
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#3: Also right on 0.002". Parallax is a bear with photographing these for some reason.
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#4: very slightly larger than 0.002". Good enough.
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#5: Bigger than 0.002" just as I wanted for thrust bearing oiling; definitely not 0.003", so let's call it 0.0025."
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OK, done with main bearing clearances on this motor.
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I removed the crankshaft, and cleaned and dried the rear of all the bearings (since you want a tight physical connection for heat transfer and spin resistance). I reinstalled all the bearings, oiled them, then laid the crankshaft in and torqued down the first four journals. At this point I rotated the crankshaft by hand and it turned smoothly with no tight spots. Great! Notice the rear upper thrust bearing has plenty of visible clearance.
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Notice the bearing fits tight on the block, and there's clearance on both ends. My dial indicator confirmed at least 0.003" in each direction, and also with a feeler gauge. LT1 factory spec is 0.002-0.008".
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A tad tight here, but let's call it 0.0025"; it's basically got 5.5 thousandths total clearance which is right in the middle of spec. And it was easy to move back and forth by hand.
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However, when I installed the #5 cap and tightened it down, I lost all clearance. And nothing I could do could restore that. No smacking, no moving the cap around, nothing. Huh. I'd loosen the ARP stud nuts and smack the crank rearwards and forwards and get 0.002" but as soon as I'd tighten the nuts, I'd lose it again, and the crankshaft definitely had a tight spot as it turned. This is a head scratcher.
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One thing you always want to do is check oil pump bolt clearance against the #5 main bearing BEFORE you install it. So I bolted the oil pump on and finger-tightened it to see.
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At least three threads of clearance there so we're good.
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