Engine Build
At the core of our Stage 5 engine build is our GTM 4.2L Stroker Kit with our billet chromoly 4340 stroker crankshaft, our billet chromoly H-beam rods and GTM spec Arias pistons with 11:0 compression. The engine block is fully prepped and blueprinted to ensure all clearances are dead nuts where we want them to be.
Standard OE clearances are all over the place with some being slightly tight and others being overly loose. We line hone the block to set a straight line for the crankshaft and use this critical step as part of setting main bearing clearances. While our high speed oiling crankshaft ensures consistent oil pressure to the rod bearings, setting the main bearing clearances to be consistent across the board spreads the loads and oil flow evenly. Controlling bearing clearances controls oil flow and oil pressure throughout the engine. The more oil that flows between the journal and bearing, the less friction there is and the oil stays cooler as a result. However, if the clearances are too loose, oil pressure drops and oil is unable to reach all the locations it needs to be with sufficient force to prevent metal to metal contact on moving parts. One thing to bear in mind is that we set clearances according to how much power the engine will be making as well as the intended use of the motor. We at GTM don’t just assemble engines; we build them right according to the application.
In addition to the blueprinting, this engine received our full GTM Micro Surface Treatment on all moving components. This is a surface treatment, not a coating and unlike a coating, does not wear off. This involves firing microscopic particles at the surface of a part at extremely high speeds. The impact of the particles does several things. First, it generates a small amount of heat that permanently changes the surface of the part, making it harder and more durable. The second thing it does, is create tiny dimples in the surface and removes the microscopic ridges and imperfections in machined surfaces. As a result, parts that receive the GTM Micro Surface Treatment are stronger and most importantly have lower friction as the surface no longer has ridges. In addition, the dimples retain oil more effectively and allow for a more persistent oil film to reside on friction surfaces.
Due to the microscopic size of the treatment media, parts that require tight tolerances such as engine bearings and piston rings can be treated in this manner without changing the dimensions of the part. When the main and rod bearing are treated, they become harder and retain oil better. Treating the piston compression rings has another benefit. Due to the micro-dimples and the elimination of micro-ridges, the rings seat faster and seal better. With treated piston rings, we noticed the vast improvement of engine performance during break-in (which was much, much shorter than non-treated rings). Out of the gate, we had more engine vacuum and there was none of the blow-by normally associated with freshly built engines.
We also treated the rod journals, main journals and piston wrist pins. With both the bearings and journals treated, friction is greatly reduced (freeing up additional horsepower) as well as increased longevity. Race teams that have treated bearings and journals together have discovered that they can double the time between overhauls as the bearings show very little wear.
The same improvements can be had with treating the pistons. This enables the skirts to retain a better oil film and reduces friction with the cylinder walls. Due to the microscopic size of the treatment media, it is able to get into the tight grooves in the ring lands and strengthen that area as well. Also, with the micro-dimpled piston crowns, the surface is able to distribute heat more evenly and most importantly, resist the formation of hot spots that micro-ridges left over from machining can create. This increases the detonation threshold and was also used on the combustion chambers and valve faces. When the treatment is performed after a multi-angle valve job, the valve seat becomes harder and is able to retain its precision shape better for improved performance over the life of the engine.
Since this engine expects to see high revs, oiling becomes a critical aspect and treating the oil pump gears increases their strength, fatigue resistance and improves their ability to move oil more effectively without undo increases in temperatures thanks to the reduction in friction. The increased fatigue strength imparted on the gears by the micro treatment will help the pump withstand higher rpms than an untreated oil pump.
With the Short Block assembled with our treated GTM Race Bearings, ARP 8740 main studs, new GTM Treated and blueprinted Oil Pump and OE main seals, we turned our attention to the cylinder heads.
The heads were fully disassembled, cleaned and pressure tested before they received a 5 angle valve job with radiused valve pockets smooth out airflow into the combustion chamber. To prevent the possibility of valve float at high rpm, we employed our GTM Valve Springs with our Titanium retainers, locators and keepers. Sealing the deal between the short block and the heads are a set of ARP L19 11mm head studs crushing a pair of Cosworth head gaskets.
Here are the pics of the complete process .....