MountainMotor

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THE ESSENTIALCRAFT OFKEEPING PROSTOCKMOUNTAINMOTORSRUNNINGText and Photos bySam Moore

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Pro Stock Mountain Motors havecubic inch displacements of 820 to825. Their capacities began muchsmaller, deriving from originalequipment big-block engines of

the ‘60s. But gradually the dimensionsbetween their pan rails grew, allowinglonger throw cranks to appear with con-necting rods measuring 7.750 inchescenter to center and 5-inch bore centerswith 4.770-inch-diameter pistons, allfunctioning within a deck height of 12inches. Today’s Pro Stock engines oper-ate on compression ratios of around18:1, run on VP Race Fuel grade Q16,and generate in the region of 1,900 hp.Depending on weather conditions, theyrun quarter-mile elapsed times in 6.25seconds at speeds close to 225 mph.

Jon Kaase Racing Engines has been adriving force in the development ofthese engines for as long as most canremember. From the beginning, whenhe worked with Dyno Don Nicholson,Kaase imposed uncompromising stan-dards in race engine building. And hisrecord of success has been impressive:He and his team have produced ProStock engines for 12 IHRA nationalchampionship winners, plus an NHRAPro Stock title. Though their businessnow includes engine part sales to hotrodders, including the supply of theremarkable Boss Nine engine, theWinder, Georgia, firm still maintainsabout 20 Mountain Motor customers,refurbishing these formidable powerplants after every 25 to 30 runs.

The engine is dismantled and the crankshaft isremoved, cleaned and Magnaflux tested.

The art of cylinder honing is never taken more seriouslythan at Kaase’s. It is the key to gaining a power outputedge while maintaining a fine, consistent pattern ofcrosshatch scratches that lubricates the rings.

New MountainMotor engineblocks areavailable in eithercast form fromC&C Motorsportsor in billet formfrom Dart. Here thebillet block isexposed to thecleaning process

Piston pins are checked for straightness,and run-out is measured to 0.0001-inch.The run-out on the average pin is usuallyaround this figure; if the indicator showsrun-out of 0.0005-inch the pin will berenewed.

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ADWhen reciprocating engine parts col-

lide (usually pistons and valves) and aconnecting rod or rods explodethrough the engine walls or the oil panor both, foreign particles are immedi-ately released into the oil stream to besucked into the oil pump rotors. Rod

bearings are often first to disintegrate,showering the pump with brass, copperand aluminum. Seasoned start-lineobservers will regale you with stories ofinexperienced drivers breaking con-necting rods at the starting lights anddriving the entire length of the track,

Until five years ago Kaase used titanium connecting rods. Today they have been replaced mainly byaluminum. On the left is a titanium connection rod and on the right is the aluminum counterpart. TheDiamond Pro Stock piston features inboard pin bosses, stiffening ribs, shorter pins and minimal skirtsto decrease frictional loses. Friction is further reduced by the use of thin .8mm top rings and Napier-style second rings. Trend’s piston pins are coated in a diamond-like carbon and retained in the pistonwith single round wire locks.

The mighty Bryant billet crankshaft resides in thealuminum block and functions with aluminum rods,bearing caps andmain caps. Aluminum is lighterthan steel, and it makes accurate line boring easier.When honing dissimilar metals, the hone is inclinedto push toward the softer metal.

The diameter of the forged pistons usuallymeasures 4.770 inches. The small-bore holesaround the perimeter of the CP pistons are gasports. These allow combustion gases to enter thetop ring grooves, imposing a force on the inneredge of the top rings and forcing them out onto thecylinder walls.

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AD The first part of the process of installing thevalves is to check the continuity of the sealbetween the valve head and the valve seat. Thisis accomplished by applying red dye to the seatsand lapping the valves into them. If continuity isbroken and traces of red dye remain, theoffending seats will be recut. Both inlet andexhaust valves are made of titanium. Thediameter of the inlet valve measures 2.680 inchesand the exhaust measures 2.040 inches.

Next, the tension of the triple valve springs ischecked. Though the desired seat pressure andthe installed height measurement change withdifferent camshaft designs, Kaase’s most regularcombination generates around 475 pounds at aninstalled height of 2.400 inches. Both inlet andexhaust valves, as well as the retainers, aremade of titanium. Installed heights aremaintained within 0.005- to 0.010-inch by addingshims under the springs. Trend Performanceprovides shims in increments of 0.015, 0.030 or0.060-inch.

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unaware that the vibration fromthe engine compartment was asignal of terminal distress. If thecamshaft can still operate, usuallythe engine will continue to keeprunning—tearing itself apart allthe way!The chief concern about

engine durability is the limitedlife of the connecting rods andalso the condition of the skinnytop piston rings. The life cycle ofthese critical parts and othersmust be strictly observed in therarified air of Mountain MotorPro Stock racing. In Kaase’s dynamometer cell,

before this engine was tested, acebuilder Chuck Lawrence leanedacross to a visitor and said, “Haveyou ever heard one of these on adyno before?” The visitor shookhis head. “It’s pretty cool,”Lawrence insisted, “I never gettired of it.” He was right. Thatsound resides indelibly in thememory. Captured in the follow-ing images is the rebuildingprocess of a Mountain Motor ProStock engine. DR

ADThis five-stage oil pump (four scavenge, one pressure) has fine mesh screens embedded in the fittings at the ends ofthe number 12 lines to minimize the risk of particles entering the pump. But in the aftermath of a blow-up, finedebris usually penetrates to the heart of the system, and the lines and pump parts have to be cleaned and the rotorsbuffed smooth if necessary. Each of the four scavenge pumps conveys oil from assigned areas of the oil pan andtransports it into the oil reservoir. The pressure pump (the one at the end) pumps oil from the bottom of the reservoirand into the filter. From the filter, it is transported into the block.

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Next, the triple valve springs are laid out for installation. Hardened seats are fitbetween the spring and the aluminum head. Oil is applied to the valve stems andthe valves are inserted into the cylinder head. Aided by a pneumatic valve springcompressor, the locks are carefully sandwiched between the valve stems andthe retainers.

Pushrods are installed, SS billetrockers positioned, their shaftstightened to 35 ft-lb and valve lashadjusted for engine warming on thedyno. Usually the clearance betweenthe exhaust valve and the rocker iszero, and the clearance between theinlet valve and the rocker is 1/8th ofa turn from tight. In this way, whenthe engine warms the inlet, valvelash will measure 0.030-inch andthe exhaust 0.020-inch.

With gaskets glued to theflanges, the intakemanifold and carburetorsare set in position.

Copper spray from an aerosol can is applied to the top and bottom surfaces ofthe three-layer Cometic head gaskets, then the heads are fit and tensioned to130-140 ft-lb.

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Curiously, the power of the vacuum pump candeflect the top skin of the alloy valve coversenough to propagate a crack around the plugholes. Welding the crack is not without itstroubles. Invariably another crack will developbeside the weld.

The best solution for sealing thecrack around the plug hole is toapply a special silicone sealer,the cost of which is around $80for a small tube.

A vacuum pump can generate inexcess of 22 inches of vacuumand is so effective it liberates 25to 30 extra hp. It has the ability toimprove ring seal and efficientlyevacuates the turbulent air and oilmist from the under thereciprocating pistons in thecrankcase, the valley area underthe intake manifold, and the valvegear chambers on top of thecylinder heads. It often dischargesto a canister through a port in thevalley (under the intake plenum)or from the front face of the rightcylinder head.

The effects of even the most powerful dyno-room fans are far removedfrom the pressurized air traveling through a hood scoop of a Pro Stockrace car at 200 mph. Still, the dynamometer plays a vital role in assessingthe engine’s condition: It allows for the examination of engine vacuum andoil pressure, of oil or water leaks, and it allows one to learn how the engineruns and whether it performs as expected. Jon Kaase’s notability rests notonly on his gift for making big power, but also in his commitment to hiscustomers—he presides over every test.

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