Engine Assembly, part 1
Part 1 of this series is about checking piston to deck clearance. Piston
to deck clearance is a measurement of of the distance between the top of
the deck and the edge of the piston. In order to get my desired compression
ratio, the block needs to be decked (material removed from the top). Although
I have the specifications for the block height, rod length, stroke, piston's
compression height, etc, it's always best to make sure everything checks out
by assembling and taking an actual measurement.
The Endyn Rollerwave pistons that I chose to use produce roughly 8.4:1
compression in this engine. Since I am shooting for about 9:1 compression,
I need to remove about .035" from the head or the block. This
can be accomplished by decking the block, milling the head, or using a thinner
headgasket. Since there is a limit to how much material can be taken from
the head, my plan is to do the following:
1) Deck the block .020"
2) Take a .005" clean-up pass on the head
3) Use the Cometic steel headgasket. It is .040" vs the .048" stock gasket.
Total material lost: 0.033"
What about clearance you say? The stock D16A1 has a country mile of clearance
between the edge of the piston and edge of the head's combustion chamber. To be exact, I measured this number to about 0.120". By removing .033", we still have over .080" of clearance (aka "quench" aka "squish"). Piston-to-valve clearance will be checked in a future article on claying the engine.
Here are the lovely Eagle/Endyn piston/rod combos, ready for the wristpin clips.
Here's the wristpin clip installed. These suckers were very high tension! Thank god for my lampshade or the one that flew across the room might have never been found.
Here's the freshly cleaned, posted, bored, and honed block.
The beefy main-cap girdle with ACL Duraglide bearings.
Balanced crank waits for pistons/rods and the girdle.
Everything is torqued down and ready for measurment
A quick glance at all of the pistons installed...
Here's the up-close picture of the piston used to measure the clearance. I layed a straight-edge across the cylinder (90 deg to the wristpin) and then used feelers to measure the clearance between the top of the exhaust side of the piston to the straight-edge. I have about .006" of clearance.
The calculations showed me that the piston-to-deck clearance should have been
about .007" (see my article Calculating Compression) and it measured to be
about .006". Feeler gauges are not the most accurate way of measuring clearance, but in this case, they validate the number that I had before.
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