Mammoth upload session tonight - boy I hope you all are enjoing reading this - it is taking longer than stripping the engine!!!!
Job #8 - measuring up
Off to my bro's to borrow his collection of dial gauges, external & internal micrometers - good on you mate
After playing around with the internal mic on the cylinders I thought I would have a look at a bore micrometer - watched one on e-bay - a Mitutoyo one like my brothers external - it went for £800
Think i'll stick with the standard one thanks.
So too cut a long story short (all measurments are in mm):
> Cam and crank runout all ok.
> Cam journals all ok
> Crank journals:
#1 59.982 - ok
#2 54.991 - ok
#3 54.991 - ok
#4 39.726 - should be 39.98
Looks like #4 jnl has been reground on its own +.25mm- kinda odd
> Big ends
#1 54.996 - ok
#2 54.996 - ok
#3 54.996 - ok
#4 54.996 - ok
If you want to measure & identify cylinders/pistons etc then I recommend you download the WC Engine Assembly PDF from the wiki as this gives the tolerances, ID marks etc.
> Cylinders - measured 15mm from top of cylinder
#1 94.005
#2 94.005
#3 94.005
#4 94.031
Cylinders should be 94.005 to 94.016 on the basis that the pistons are stamped as 93.980 so no problems here either - #4 is a bit worn but within the measurement variance of a .001" micrometer. Cylinders are all clean inside, no scores or scratches and measuring in the opposite axis shows an ovality variance of only 0.025.
Cylinder #3 has a chunk missing from the lower skirt, this is consistent with the case damage and I guess this is where the crank snapped and stabbed a rod/piston into the case
> Pistons look quite "tired" All are marked as Mahle so guess are OE.
Nos. #1, #2 & #3 all have a "+" weight markings on them and also when cleaned up all have nicks in the valve cutouts. It is old damage, below the soot but all the same. Doesn't look bad enough for a valve to have dropped and hit them and is too consistent across all the pistons - odd
#1

#2

#3

#4
I am wondering if the deck height is low enough that an over adjusted rocker would push the valve far enough to just slightly catch the piston crown but thats sounds a long shot - any thoughts?
No #4 has a "-" weight marking and hang on - it has no marks on the crown and looks much newer! Someone has fitted a replacement piston in #4 and managed to pick one from the alternative weight group
Lets measure them up.....measuring 15mm from bottom of skirt
#1 93.9546
#2 93.9546
#3 93.9038
#4 93.9292
Remember the marking on the piston top said 93.980mm so not bad. Then measured the horizontal axis
#1 93.7006
#2 93.6752
#3 93.6752
#4 93.6752
Hmm, these puppys look a bit oval!
Now I'm not Sherlock Homes but, I'm wondering if the crank had excessive end float ( didn't check this before I stripped down) and this slopping around in the horizontal plane has caused the wear on the big end (rods rocking) and the ovality of the pistons (wear in the horizontal plane)
> Piston rings
End gaps are all easily within tolerance as are the side gaps so no problems there
So the summary.........
No obvious failings, but a few questions.
Mismatched pistons, older ones have a fair bit of scaring on the crown, slightly oval.
Crank and rod bearings not good condition and slack.
Some scars on the case and a couple of old, re-used studs.
No obvious signs of the reason for lack of compression on #4 but still need to strip down the heads. Knocking could have been coming from the crank/big ends - will check out the lifters as well when I do the heads.
Not that impressed with the engine "rebuild" 10,000 miles ago so far, I would have to say.
Got RSI from typing now so thats enough for tonight
MM