Another Broken XPAG

Adjusting an E-type upper timing chain

E-type upper chain adjustment

While the radiator was out of the way, which provides superior access to the front of the engine, I took advantage of the opportunity to check the upper timing chain adjustment, which is set manually.  The owner had asked us to check it as there is auditory evidence of a chain rattle on the overrun.

Gear for eccentric adjuster

Adjustment gear

Because the adjustment was perfectly tight my money is on chain stretch.  The picture on the right is of the gear on the upper chain eccentric.  To adjust the chain you depress the plunger located at about eleven o’clock and turn your tool counter clockwise.

E-type radiator installed

Radiator in place with Kenlowe fan

As mentioned previously the ‘direct fit’ Kenlowe fan kit proved to be anything but.  There really was no provision at all for mounting it to the radiator so Rodney at B&R’s Garage fabricated a pair of mounting straps, and much to my chagrin it would not clear the mounting bracket for the old fan motor, so I took out my spotweld cutter and took the bracket off.  But all’s well that ends well. so wiring it up and replacing a couple of hoses are all that remains.

sign of severe heat on #4 con-rod throw

This doesn't look good, either

Another week, another broken XPAG.  For the second time in two weeks we’re poking around inside an MG TD engine searching for the cause of a failure.  In this event the physical symptom was a severe engine knock.

As seen here, #4 connecting rod throw has the waves of heat discoloration which are consistent with a significant bearing failure.

signs of a previous failure

Washers under #2 con-rod castle nuts

In the picture to the left, a close examination will reveal the presence of a pair of grade 8 SAE washers under the #2 connecting rod castle nuts.  When I pulled the bearing cap off the#4  con-rod, the bearing inserts, a +.050″ undersize,  were well and truly destroyed.

Although this might look like a riddle inside an enigma, the evidence suggests a previous catastrophic bearing failure on #2 rod journal.  In order to make chicken salad out of chicken scratch, the machinist undercut the con-rod enough to be able to machine it round again, but with so much material gone he needed to shim up castle nuts with washers in order to be able to install the cotter pins thru the castle nut slots.

broken # 4 exhaust valve

Last week's failure:#4 exhaust valve, broken thru the keeper groove and saved by an o-ring

The crankshaft must have been an awful mess too, to save it the crank guy cut the rod journals .050″ undersize.  Because of the huge weight differences rod to rod a balance job would have been a good idea, but none was in evidence.  However the fatal mistake was in not reconditioning the other connecting rods at the same time.  As we now know, #4 failed soon after.  What this means is a new crankshaft and probably a pair of connecting rods as well.

So here’s a picture of last week’s TD engine failure whereby the #4 exhaust valve broke thru the keeper groove and was saved from a nasty encounter with the on-rushing piston by the foolish o-ring that was the examplar of 1950’s upper cylinder oil control.

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