Can you hear the pistons ringing?

And I thought I was through with clearances and tolerances…  Seems that it is a good idea to check the ring gap before installing the rings onto the pistons.  The rings go on the pistons and provide compression and such… each piston has 5 rings * 8 pistons equals 40 rings.  Luckily I only need to check the gap on the top 2 of each piston.. so only 16.  This process involves inserting the bare ring into its piston bore, squaring it up about an inch down and measuring how much gap.

15 completed within tolerance and I begin the last ring – why is it always the last one?  This ring was the one I had installed onto a piston to use during squaring the rings.  Installed onto the second ring as a stop and pushed the rings into the bore.  I thought I was sunk as I had to keep using increasingly larger feeler gauges…  but it topped out .018, still within tolerance of .010-.020.  All of the others came in at .012.

Onwards – installing pistons.  Put on the oil ring and position the seam, install the top oil scraper and place the gap at 2 oclock… readjust the oil ring because it just overlapped… install the bottom oil scraper and place the gap at 4 oclock… now go back and readjust the top oil scraper.  Install the second compressor ring and place the gap at 10 oclock, then the top compressor ring and place the gap at 7 oclock… repeat 7 more times.  Did I mention that this is mind numbing, but don’t lose focus because you don’t want to scratch the piston or have a ring shoot off the expander tool across the room (only happened once, the shooting part).  Point is that the ring gap positioning should not be on top of each other.  I've read that when folks tear engines apart - the ring gaps positioning is nowhere near where they started - just sayin...

Get your handy dandy compressor tool and crank it onto the piston compressing the rings tight against the piston that I just dipped in oil, that’s right, this is a slippery, messy process.  I was a bit anxious with the first piston as I banged it into place, but it went right in just like the online videos and books said it would.  Quickly followed by #2, 3, and 4.

Now #5 started just like the others and when I got to the banging part it started on down like it’s supposed to but just before slipping all the way in, the top ring popped out and hung on the bore.  CRAP.  Flip the engine over and bang it back out.  Put the compressor back on and start banging again.. again it popped out, then again a third time.  What is going on?  When releasing the compressor from the piston after the third attempt I watched in slow motion as a little screw popped off the tool and dropped down a water jacket hole. NOOOOOOO!!!  Seem this screw was part of the tensioning mechanism of the compressor tool and wasn’t properly providing compression on the bottom band of the tool and was the culprit for the ring popping out.  Took me 20 anxious minutes to locate my “magnet-on-a-stick” tool and fish out the screw.  This is when my friends words of wisdom popped in my head – “Don’t work on the engine when frustrated”  go to bed.

The conclusion of this is that the tool was a crappy loaner from the local auto store.  I ended up buying a proper quality tool and finished up the piston installation the following day

look what i've done - nice paint.  Pistons installed, timing set installed.

Do you have a tolerance for clearance?

I finished the pre-build of the engine over the past weekend, and didn't take any pictures.  That's ok because I took it all apart again.

It is called a pre-build because this is when you double check the tolerances, clearances, and fit of the rotating assembly... the cam, crank, pistons.....

Goes like this - wash the block, crank, and cam with soap/water and pressure wash the whole thing, then quick get your compressor on it to dry it out.  This was the first time I had the pressure washer out since moving here, although the neighbors have made good use of it, and I got sidetracked cleaning a section of the driveway... now I have another project to add to my list because I have one clean section and 5 dirty ones.

First put some oil on cam bearings and carefully insert the heavy cubersome bastard making sure not to nick the bearings... spin it to see if spins freely - now take it out making sure not to nick the bearings and inspect for shiny wear spots.  Didn't have any, good, now put it back in again making sure not to nick the bearings.  by the way, this is done from the front of the engine into a blind hole the entire length of the block - and the rear hole had already been sealed so the last bearing was a bitch.

Then wipe out the main bearing saddles, check the main bearings - fit them in and align with the oil holes, light coat of oil on the bottom portion, lift in the HEAVY crankshaft, and fit the top main bearings and caps.  There is a little tolerance gauge called plastigage that is a piece of green thread.  You can see it below (this is the piston rod for those that can tell) and torque down the bolts to spec.  105ft/lbs for a 351W.

loosen it all back up and measure the gauge to see how squished it got.

 

Do this for each of the 4 main journals, and each of the 8 piston rods - Oh and you can't move/turn anything while you do this or you mess up the reading.  All of the tolerances checked out against the shop manual I got for this motor.  You know - the book with the greasy fingerprints and bad black/white photos circa 1969.

At the end of this process, you have the cam, crank and all 8 pistons installed and turning making sure that nothing touches.. then whack on the timing set onto the crank and cam and now check for endplay on both the cam and crank.  These are good too.

Did I mention the oil pump and checking to see if the crank counterweight misses the shaft?  The pickup screen and how much clearance there is to the bottom of the oil pan?  How much clearance there is when the piston is at the top of the cylinder?..... blah blah blah.  This took 4 days.

This weekend will begin the painting of the block and prepping for the real assembly.  I've got lot's of shiny parts to go on this thing and I can't wait to see how it looks.