Once again I was at a loss for the appropriate expression (@#$%^&%$#$%)
after finding that the two larger diameter through-bolts (tension bolt? whatever)
on my 20B had not ever been torqued. I had mentioned a while back that
when running my engine on the plane I had noted a small coolant leak coming
from a through-bolt at the bottom of the rear housing. With the rear
engine mount plate and re-drive mounted it was not possible to get a wrench on
it.
I was about to begin the process of removing the re-drive,
etc. to replace the seal, when, for whatever reason I grabbed a couple of
wrenches to put on the larger bolt at the top just to check what size it was
(21mm). As I was fitting the wrench onto the head I thought I saw the
bolt move. No way. I flipped the wrnech over and put the box end on
the bolt – THE BOLT WAS LOOSE! It took at least a full turn to get
to a torque of 25 -30 ft-lbs. I checked the 17mm bolts – they were
fine. After removing the starter and a couple of the re-drive plate
spacer blocks, I was able to check the other bolts. The bottom 21mm bolt
that was leaking was also loose. It took more than half a turn to get it
tight.
Best I can guess is that all the smaller bolts were torqued,
but whoever did the job, forgot to tighten the 2 21mm bolts. It is just unbelievable
to me that an “expert” building up an engine for an aircraft could
make these errors.
I was upset by failed attempts by Atkins on custom exhaust
and intakes, but I rationalized that at least on the engine block he really
knew what he was doing. But later found at least four major errors;
- Installing 9.0 compression rotors in a NA engine
instead of 9.7, and then arguing that the lower compression was better. I
agree that at high rpm, 6500+, it won’t make any difference; but
Mazda test data suggests about a 4% penalty at my cruise range of 5000 –
5400 rpm.
- A custom longer oil pickup tube for my deeper pan
which was; a) too long to fit in the pan (which he had in his shop), and
b) leaked air around the flange weld so the oil pump would suck air
bubbles.
- A front e-shaft pulley with timing marks that bore no
relation to the timing pointer. I guess the because of a stock 20B
pulley and a 12A front cover. This took some hours to resolve during
the dyno testing.
- And now the two tension bolts that had never been
tightened.
I can only hope there will be no further “discoveries”.
The last time I talked to David (months ago) he mentioned that he was no
longer providing engines for aircraft. Good idea – just too late.
He did my engine about 4 years ago.
A couple of questions: Why are two of the bolts
larger? What is the torque spec on these bolts for the 20B? I seem
to recall 26-28 ft-lbs. I can’t get a torque wrench on the bolts
without removing the re-drive, engine mount and flywheel, but I have a pretty
well calibrated arm.
Al