In Chassis vs Out of Chassis Rebuild

2020, Boost, Catalyst, Rebuild -

In Chassis vs Out of Chassis Rebuild

Are you running Max Mileage Fuel Borne Catalyst in your diesel fuel and your Harley Davidson?  If not, you are not doing justice for your engine.  The catalyst will burn 60% or more of the soot and carbon in the combustion chamber and it ignites diesel fuel 33% faster than diesel fuel alone.  Webasto and Espar cab heaters will not have to be cleaned because there will be no soot in the firing chamber. If you work on your truck and must change the exhaust pipes, guess what, you will not get dirty because there is no soot in the pipes after a couple months of running the catalyst.  Many variable geometry turbocharger failures are caused by a stuck actuator, and the catalyst eliminates that problem also. This is Magic Fluid!

In Chassis or Out of Chassis engine rebuilds: We are getting many questions as to the difference between in-chassis (in-frame) and out of chassis engine rebuilds and how do you know which one your engine needs.  So, let’s start with the chassis. The chassis is the two frame rails, the front and rear axles, and the suspension. The engine, hood, front bumper, cab, bunk, and fifth wheel all are connected to the chassis.  When performing an in-chassis rebuild the engine stays in the truck while it is being rebuilt.  The crankshaft stays in the engine block and the surface of the engine block where the head is bolted on cannot be resurfaced.  The bore in the block where the crankshaft turns cannot be line bored, so it’s imperative to be able to read the wear on the main bearings to determine if the crank bore is straight before continuing with the in-chassis rebuild. 

A basic in-chassis rebuild consists of installing new rod and main bearings, a 6-cylinder rebuild kit (including liners, pistons, rings), a reconditioned cylinder head, six injectors, and all new gaskets.  This is a basic and economical rebuild.  At Pittsburgh Power we prefer to balance the connecting rods, pistons, and pins to ensure a balanced and smooth running engine.  We always decide to install a new torsional damper on the front of the crankshaft along with a mercury filled engine balancer, the end goal being smoothness and longevity.  We cut the upper counter bores and raise the liner protrusion by .001 over the OEM high spec, this assures the head gasket will not blow or leak combustion. A ported and ceramic coated exhaust manifold and performance turbocharger are optional upgrades. The result is a decrease in exhaust gas temperature by 125 degrees, 20% more exhaust flow, ½ or more miles per gallon, and about 80 horsepower. We then check the calibration of the ECM, this is to assure the timing, injector flow, and increase torque and horsepower if necessary. We also check that the ECM does not show fault codes. We check that there are no components ready to fail. Our experienced technicians look for anything that is not working on the truck or engine at this time. Optional is a new camshaft if needed, oil pump, water pump, alternator, air conditioning compressor, FASS Fuel System, Bull Gear on DD3/4 Detroits, by-pass oil filtration system, Fleet Air Filter, and the starter.  The end result is a smoother running, better pulling, and longer lived engine that is a pleasure to drive and will not work the operator to death.

Out of Chassis rebuilds consist of removing the engine from the chassis, disassembling it on an engine stand, and removing everything down to the bare block. The engine block and crankshaft are then sent to a machine shop where they are cooked in a hot tank to remove all the dirt, grease, and paint.  The next step is to magnaflux the block and crank to see visible cracks. The engine block is now checked for straight line bore, resurfaced and squared, and upper counters bores cut.  The crankshaft is straightened (we have found them bent as much as .028 thousandths) then polished so the rod and main bearings have a smooth surface to ride on.  The engines are in the machine shop for at least one week. On the second week the block and crank are returned to the shop, the block is mounted on an engine stand and the assembly process begins.  Most of the time all the above-mentioned components are rebuilt, or exchanged for rebuilt units, and installed on the engine.  All the gears in the front cover of the engine are inspected for wear, then installed during the reassembling process.  No part of the engine is left unattended, including all the bolts, nuts, and fittings.  The result is a new, blueprinted and balanced engine that should run in excess of 1 million miles when driven properly and maintained. It takes one week to assemble the engine. On the third week the engine is installed in the chassis with new engine mounts, hoses, belts and anything else that needs replaced such as the radiator and charge air cooler while the engine is out. This entire process usually takes one month and typically costs about $40,000 (but can be more or less). This is NOT an economical process. It’s labor intensive with many parts.  However, this is necessary when the engine and truck have about 2 million miles on the odometer.  If we gain you one mile per gallon, the fuel savings pays for the engine rebuild.  As the saying goes, the bitterness of poor quality remains long after the sweetness of a low price is forgotten. Quality costs money.          

Fuel Mileage with speed takes power and is only obtainable with a free running truck.  It’s impossible to get six plus miles per gallon while running 70 to 75 mph at 18 to 20 pounds of turbo boost.  With a 3406-E Caterpillar, or single turbo C-15 Cat, 12.7 Detroit, 14-liter Detroit, ISX Cummins, N-14, or Big Cam Cummins, the turbo boost on the level must be under 10 PSI to get 6 plus MPG.  If you desire to be 7 - 8 or more MPG the turbo boost on level terrain must be 4 to 6 PSI.  Many of you think this is impossible, and it is if you don’t spend the money to make changes to your truck.  Yes, it takes horsepower and torque to be able to obtain great fuel mileage, however, that is just for going up the hill or mountain.  It’s on the level where fuel mileage is obtained and to do this turbo boost must be kept low.  Here is the recipe to lower  turbo boost on level terrain: it starts with the air filters, Fleet Air Filters, washable foam are the best, then the turbocharger must be able to make enough turbo boost on the mountain to keep the exhaust temperature 1300 degrees or less (this is with the thermocouple on the hot side or in the exhaust manifold).  If the turbocharger is too small, it will produce fast boost, great for city driving, but terrible for pulling a load across the interstate.  Most mechanics today do not understand back pressure in the exhaust system, they think high boost is the way to go, well it’s not. Unrestricted air and exhaust flow are what you need.  Stock turbochargers are usually too small and restrictive, OK for city driving, not for 70 to 75 miles per hour on the interstate.  The exhaust manifold must be ported and ceramic coated, flow bench tested, have the 90-degree turns eliminated, and be able to increase exhaust flow by at least 20%.  The muffler must be of a straight through design, not a stock muffler with the baffles punched out of it. And forget the straight 8” and 10 “ stacks sticking way up in the air, they do not work.  The exhaust cools down too much in the stack and the piston on the exhaust stroke must work too hard to push the exhaust all the way to the top of the stack.  Stay 7” or less on the diameter of the stack and keep it as short as possible to clear the trailer.  A “weed burner” exhaust is the best for fuel mileage.  I know it doesn’t look cool on a 379 or 389 Pete, W900-L Kenworth, or Freightliner Classic, but it’s worth it.  

Now we come to the gearing: overdrive was not meant to pull a load, let alone double overdrive.  That is a bad design by engineers that do not understand free rolling and the amount of horsepower lost in gearing.  The Allison World 6 speed transmission is the worst offender of this free rolling principle.  Likewise, the Eaton, Meritor, standard, and auto shifts with a .73 overdrive are next in line for the worst transmission.  Now YOU must take it upon yourself to change the rear gearing to run these transmissions in direct gear. Only use the overdrive portion of the trans when you are empty, bobtailing, or going down a long grade.  I love the 13 and 18 speed Eaton transmissions when combined with differentials that have a 2:64 or 2:50 gear ratio so the load can be pulled in direct gear. 80 horsepower is saved by gearing this way and turbo boost pressure will be lowered by around 3 PSI on level terrain.  Think about this, 10 psi of turbo boost is about 200 to 250 HP, 20 psi of boost is around 400 HP.  How are you going to make fuel mileage at 20 PSI of boost on the level?  YOU CAN’T.  I’m not saying you can’t drive at 70 to 75 mph and get fuel mileage; we must be able to get the turbo boost under 10 psi to do so.  The lower the turbo boost on the level terrain, the better the fuel mileage and the longer the engine will live. 18 to 20 pounds of turbo boost on the level will cause premature engine wear too. Speaking of avoiding premature engine wear, don’t forget to run Max Mileage FBC in your truck! 

Written by;  Bruce Mallinson

Pittsburgh Power Inc.  

3600 S. Noah Dr.  Saxonburg, Pa. 16056