Bottom End Assembly

In this installment, the bottom end rotating assembly is assembled.  To start, I again relentlessly wipe the bores down to make sure they are as clean as possible.  Acetone on a white shop rag, followed by Dexron ATF (note: I used the Dexron III-type fluid, which is conventional.  The Dexron VI is a synthetic.)  The rags came out clean, so the bores must be clean :)  To make sure the crankshaft is also free from debris, I used 75psi compressed air to blow out the oil gallery before installing the threaded pipe plugs.

First up, I installed the main bearings.  These are the OEM bearings, with a dry-film coating from the first buildup.  They showed virtually no wear, so are being reused.  The main bearing studs, and outer perimeter sump studs are installed into the block.  The coarse threads get a light coat of 30wt oil.

 

 

 

 

The main bearings were lubed with Torco assembly lube, and the crankshaft was carefully set into the block.  At this point, I also installed the front crankshaft oil seal o-ring, lightly lubed with oil.  By this time, the A136 Permabond had arrived from Jerry's Gaskets, and was applied to the sump.

 

 

The main bearing studs' fine threads, as well as the washers and nut face were lubricated with ARP's Ultra Torque lube.  The mains were torqued in steps--30 then 52 ft. lbs in the order specified in the service manual.  Finally, the M12 studs on #1, #3, #5 bearings were torqued to 80 ft. lbs.  The perimeter studs were torqued to 24 ft. lbs.  The crank spins easily after all the nuts are torqued.  I also checked the thrust clearance, which was within spec at .008".

 

 

Connecting rod bearings were installed in the rods, lubed with Torco.  The piston rings were carefully aligned, with the gaps at least 120 degrees apart.  The skirts and rings were given a light coat of oil before insertion into the bores.  An ARP tapered ring compressor makes this process pretty easy.  The rod caps and new Carrillo SPS multiphase rod bolts were installed, lubed with ARP Ultra Torque.  The bolts were stretched to the middle of the Carrillo spec, .006", using an ARP rod bolt stretch gage.  The proper stretch was achieved with 58 to 60 ft-lbs of torque.

 

 

Finally, the oil pump, crank sprocket, guides, chains and idler gear were installed.  New seals on the pump, anti-seize on the crank gear, and Loctite 262 on the bolts where specified.  I also took the occasion to disassemble the idler gear and apply some light assembly grease to the needle bearings.  And that's as far as I am going before assembling the heads and timing the camshafts.  Starting to look like an engine again....

 



Rotating Assembly prep and other things

Been a few weeks since I last posted about this build.  An impromptu vacation and a couple of customer calibrations to finish came first.  Several small things have been completed, and at this stage I'm about to drop the crankshaft into the block.  Just waiting on a fresh bottle of A136 from Jerry before I can finish the bottom end.

Combustion Chamber volume:  I measured the volume of the combustion chambers with a 100cc burette.  Since the first build, we are using new copper-beryllium valve seats and larger intake valves, so I needed to confirm the chamber cc's to determine final compression ratio.  Sealed the valves and the plexiglass overlay with white lithium grease.  The results were a little surprising.  the chambers measured 47cc's.  (I was expecting 49cc)--the new valve job reduced the volume by 2cc's.  That leaves the final compression ratio at 14.8:1.  Was aiming for closer to 14:1, but will be running race fuel anyway, so not a big deal.  << Update: after assembling the shortblock and taking accurate piston-to-deck measurements, the final compression is 14.55:1.  The pistons are .003" above the deck at TDC.>>

Piston pin assembly:  Back to the bottom end, I installed the round wire locks in one side of each piston pin bore.  These locks can be tricky to install, but with a little practice and a small flat-blade screwdriver, it got a lot easier.  These are .068" thick round wire locks, and were installed with the ends at 6 o'clock relative to the pin bore.  A bit of assembly lube (Torco MPZ HP) on the piston pin, and ready for the other lock.  It is important to get the pistons oriented correctly on the rods so that the large chamfer on the rod is facing towards the crank cheek, while the intake valve pockets also face the inside of the engine.  Seems simple, but I double and triple checked this before locking the pistons to the rods.

Piston Rings:  This build uses Total Seal AP steel rings.  All the end gaps were set by the machinist, so I won't show that here.  Top and Second end gaps were set at .019".  The rings were marked specific to each individual bore, but the bore dimensions were so identical, they could have been installed in any hole and been fine.  Nevertheless, I installed them in the same position they were set up for.  The oil rings use a support rail because the pin bore intersects the oil ring groove.  The support rail has a raised "dimple" on one side, which needs to face down and centered in the pin bore opening.  The support rails were installed first, then the expander, then the two scraper rings.  These are custom 3mm oil rings, at 14# tension.  The second ring is .043" Napier style, so orientation is important.  The top ring is .043" steel, and is installed with the inner chamfer facing up.  Checked the vertical clearance between the rings and piston-- all <.0015", which is the smallest feeler gauge I have.  Tight vertical clearance is expected with these high end rings and gas ports.

Crankshaft checks:  One other thing I checked at this stage is the straightness of the crankshaft.  I had no reason to believe there was a problem, but checked it nonetheless.  This was done by placing the #1 and #5 upper main bearing shells in the block, and placing the crank into position.  Using a dial indicator on the center crank journal, I rotated the crankshaft a complete revolution.  There was zero measurable runout, so all is good.

The crank came back from the machinist with the threaded oil plugs removed.  Using compressed air, I blew out all the oil passages.  They were clean anyway, this was just a precaution before installing the plugs.  The pipe plugs get a light coat of Loctite 565 sealant before being installed.

Next time I hope to install the crank and pistons and finish the bottom end.