| The rebuilding
of an aluminum block engine presents some circumstances and
problems not normally incurred in repairs on the standard cast
iron engine. There are some special steps to be taken in order
to insure a long lived, well performing job.
Many
of the early engines had a cast iron sleeve which is not replaceable.
Therefore, it is very important to check manufacturing specifications
as to the maximum amount of overbore.
With the later engines such as the
Chevrolet Vega 2300 having a high silicon aluminum block,
there are two accepted methods of remanufacturing.
The first method which reproduces the
original bore finish with the hard silicon particles protruding
was developed by the Sunnen Products Company.
This process by a series of honing
and polishing operations removes the surface aluminum, allowing
the silicon particles to protrude that the pistons and rings
ride on. Information covering this procedure can be obtained
from the Sunnen Products Company.
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Both
of these methods have proven to give excellent performance and
durability as long as the procedures were closely and correctly
adhered to.
When tightening
bolts in aluminum engines, the use of a torque wrench according
to the manufacturers recommendations is an absolute must.
Over torquing will cause the aluminum to bulge in the cap
screw area, preventing mating of flat surfaces, mis-alignment
of main bearing caps, incorrect bearing clearance and.crush.
Improper tightening of the cylinder heads and main bearing
caps can distort the cylinders, causing blow-by and excessive
oil consumption.
Aluminum threads should be cleaned
and lubricated to prevent damage to the threads and allow
accurate torquing. Damaged aluminum threads can be retapped
and heli-coil inserts used to restore original thread size.
Aluminum engines should have year round
protection with an ethelene- glycol -water solution and rust
inhibitor. This will prevent corrosion or cooling system clogging.
There are also some engines utilizing an aluminum front cover
and water pump mounting. Some problems have been reported
where due to lack of protection the aluminum housing was corroded,
allowing a coolant leak directly into the oil pan.
With these things in mind, the successful
overhaul of the aluminum engine is no more difficult than
conventional cast iron. |
