The Step By Step Assembly of a 2.9 Big Bore M96 engine
By Jake Raby
In the following pictures you'll see what is required to assemble a Porsche M96 engine at the Performance Level. This engine started life as a 2.5 Liter M96 from a 1999 Porsche Boxster that had suffered several different modes of failure to include slipped sleeves, failing IMS, and ultimately the "D Chunk" failure that ended in a catastrophic loss of life for the engine.
This engine had previously been "Remanufactured" by Porsche as part of their replacement engine program and the case had been welded in several areas, MMC cylinder sleeves installed, and other standard procedures performed by the Porsche Remanufacturing program. The outside of the case was marked with the tell-tale blue paint so many of these problematic reman engines have been identified by.
We chose this engine case for our latest test engine, because it was by far the WORST crankcase that we had ever experienced, and if any engine was doomed to fail while creating higher performance, this one was it! In the pictures you'll notice that the case has several stains and may appear dirty, but these are made much worse by the camera and lighting of the assembly area.
Note: We'll be leaving the big, fancy words for another day and I'll do my best to help the "normal people" reading this article understand in laymans terms what the images depict.
We'll begin with the "Heart" of the engine. The Crankshaft
This crankshaft started life as a stock stroke unit from a 2.5 liter Boxster, it was subject to our stroking process that took it's stroke to 78.4mm. The Crankshaft was also subject to Ion Nitriding process to enhance it's wear resistance and to acheive the best longevity along with our PC3 (friction reduction coating) coated main and rod bearings.
The crankshaft along with the remainder of the dynamic assembly was then balanced and indexed using our own in-house digital dynamic balancing equipment.
Here the reworked and updated 78.4mm Crankshaft is pictured after being sterilized, ready for assembly.
Here the Crankshaft "Carrier" or "Cradle" is after being measured for wear and straghtness, prior to the main bearing inserts being introduced. This is a two part assembly that assembles much like the crankcase halves would in an aircooled Porsche engine of yesterday. This carrier houses the main bearings (14 inserts) as well as the shims used to set crankshaft end play.
Here the R&R Pro Billet Chromoly Connecting Rods supplied by LN Engineering. These units are MUCH stronger than stock as they feature a stronger H beam design as well as ARP 2000 rod bolts. The M96 engine has become notorious for rod bolt failures with the OE rod bolts, these "Overkill Engineered" rods and their rod bolts will never have that problem! These best part is a full set of these rods costs less than Porsche replacements and they can be rebuilt due to their design. The stock rods are disposable as they utilize "cracked cap technology" like most other modern engines. The markings on the rods depict the actual bore dimension of the rod with the bearing installed and the rod cap torqued as part of our blueprinting procedures.
This is a reality when an engine is assembled by a detail oriented Human, not a Robot.
Here the Flat 6 Innovations custom main bearings are shown with the PC3 Friction Reduction Coating applied, ready for final cleaning and assembly into the crankshaft carrier assembly.
Main Bearings installed into the carrier, ready to be lubricated for crankshaft introduction. (Running clearances were previously measured, verified, and recorded)
Insertion of a main bearing insert into the crankshaft carrier.
Both portions of the crankshaft carrier with inserts installed.
After some heavy lubrication with our engine oil used for assembly, the crankshaft is introduced into the crankshaft carrier.
The crankshaft must be introduced into the portion of the carrier that houses the relief for the crankshaft end play shims.
Only one half of the carrier assembly has these reliefs on the center main saddle.
Another shot of the relieved center saddle...
Now for a shot of the center saddle with an end play shim held in place. These shims are used to set Crankshaft "end float" or "end Play" which is basically the fore/aft movement that is built in to the dynamic assembly. These shims wear and are replaced as part of our update process with units that have been Cryogenically enhanced for longer life. Note the oil slots in the outboard facing portion of the shim, this is critical to the life of the shim and crankshaft. If these are inslled backward, issues will occur!
Here I have set the static "end play" of the crankshaft with both my new end play shims installed into one half of the crank carrier. This is rechecked after the entire carrier is installed and torqued, ours only changed 1/2 of one thousandth of an inch, resulting in our target end play of .0045 being attained perfectly.
Marrying the two halves of the crankshaft carrier together...
Experience has taught me to assemble engines by feel... Here I am rotating the assembly as I tap the carrier housings together by hand.
Torquing the crankshaft carrier bolts to our updated specs...
"Feeling" the assembly to note tight spots or something that triggers my sense of danger. This assembly was so smooth it felt like warm butter was used for assembly lubricant! Perfect!
LN's R&R Pro Connecting Rod with it's matching PC3 coated rod bearing inserts and ARP 2000 Custom Aged rod bolts.
JE (FSR) forged side relief pistons designed by LN Engineering with their matching, weight balanced wrist pins.
LN connecting rod and piston assembly ready for piston rings and introduction into the 1-3 cylinder bank.
This view illustrates the Anti-Scuff coatings applied to the piston skirt.
The trio of connecting rods, rod bearings & caps, and pistons ready for insertion into their respective positions in the LN Engineering "Nickies" big-bore prepared crankcase.
Custom low tension Piston ring package after being checked for ring end gap and fit into the pistons. These have to be cleaned rigorously to remove all impurities left over from the manufacturing processes. Cleanliness and sterility is key when woring with tolerances this tight within any engine! All engine parts are cleaned meticulously several times during the assembly process leading up to final assembly.
This crankcase began life with an 85.5mm bore size, as a 2.5 liter engine. Here you see the 3.5mm oversize accomplished with LN Engineering "Nickies" cylinders. Nickies is short for Nikasil, a process that utilizes Nickel, Silicon and Carbide to create a super hard, wear resistant plating that allows for lower friction and lower oil temps. Nikisil was employed by Porsche in the aircooled 911, but wasn't applied to the M96 from the factory. (Damn German Accountants!) LN Engineering uses a process called NSC with similar wear and performance to Nikasil (a trademark of Mahle) that has been proven in their complete series of Nickies aircooled cylinders for Porsches.
These LN Engineering "Nickies" cylinders are what open the doors for us to increase longevity, increase reliability and do so with additional performance without worry of overheating or cylinder failures even at increased displacement or output.
Here I am installing one of the piston and rod assemblies into the crankcase...
A view from the opposite side while I install Piston #2...
Position #1 has it's piston and rod assembly installed along with the rod bearing insert and is pushed to the top of the bore in anticipation of the crankshaft carrier assembly being dropped into the crankcase...
Positions 1-3 with their Pistons situated at the top of the bore. Dropping the carrier assembly in comes next...
Carier assembly with IMS drive chain, tensioner paddle and the connecting rods for cylinders 4-6 installed and torqued.
IMS drive chain and IMS are coupled to the crankshaft to complete the assembly thats known as the "carrier combo". These will be ready to drop into the crankcase half shortly. Note the Upgraded LN Engineering IMS assembly. This was an earlier four bearing design with conventional roller ball bearings only compatible with what were originally dual-row bearing intermediate shafts. More recent versions from LN use a revised three bearing design with hybrid ceramic bearings and can be used to upgrade either single or double row intermediate shafts.
Fitting a new seal to the crankshaft scraper assembly. Note the IMS tucked in place.
Another view of the crank carrier combo showing new, updated chains in place and still a little stiff as well as new wear pads for the tensioner paddle and guide. At the time this engine was built, we did not have LN Engineering's billet IMS tensioner blade which we since then use on all rebuilds in place of the original cast part.
Lubrication during assembly is key! All components that come into contact with another component must be lubricated or wear will be experienced during assembly and initial start up. As we build by feeling, areas where additional sensitivity to feedback is needed, we use straight 30wt break-in oil. On items like chains and wear pads, a thicker assembly lube like that supplied by CMW Oil Co. is good where you want to keep dripping and drainage of lubricant to a minimum.
Here we have dropped the crankshaft carrier combo as a unit with timing chains attached into the crankcase half.
Note the connecting rods for cylinders 4-6 protruding from the carrier unit.
After tightening a few fasteners and attaching the cylinder 1-3 rods and rod caps onto the crankshaft assembly I roll the crankcase half over with the crank carrier combo installed to verify and record our cylinder 1-3 deck heights. With the LN procedures the case decks are surface ground and this means excellent accuracy, all our deck heights were within .0015 of each other, which makes for even combustion balance and a very smooth running engine!
Here we have installed the 4-6 crankcase half and inserted the special tool used for piston alignment for the 4-6 position pistons.
Another view of the tool inserted through the access hole. Through this hole we are about to be assembling the entire 4-6 bank of the engine using only skill, sense of feel, and the aid of a borescope to check our work.
Cylinder #6 with it's piston installed and pushed down the bore with the alignment tool inserted through the access ports in the cylinders. This special tool aligns the piston and the connecting rod to aid with the assembly of the wrist pin and retaining clip. This particular cylinder and piston are THE MOST difficult to assemble as they are deep within the confines of the engine and all work must be done very patiently with the use of sense of feel and the borescope. The wrist pin clip must be inserted into the piston effectively and one small goof results in a failed procedure and a clip that fires it's self into the crankcase, requiring tear down to fetch it!
If this occurs hours of labor are lost...
Here you see one of our borescope units illustrating the piston and connecting rod are aligned properly and ready for insertion of the wrist pin and retaining clip. If you have trouble identifying what is what in the image, you can see the connecting rod pin end bushing (a goldish color) with the two oil holes for pin oiling.
Who said engine Building wasn't surgery! This is literally all that can be done to visually inspect the work area deep within the M96 engine while assembling the #6 piston assembly onto the connecting rod.
Having aligned the piston with the connecting rod and checking my work with the borescope here I am inserting the wrist pin into the access port that leads into the #6 cylinder where it will marry the piston and connecting rod forever. This is done with yet another special tool...
Here the clip that retains the wrist pin into the piston. It is loaded into the end of another special tool that is designed to insert it into the piston. This tool is fed deep into the engine, where it must be inserted with extreme care into the piston to ensure it is seated properly and deep enough to drive the clip home. This is done with only the sense of feel and some measurements and index maks we have scribed onto our tools.
STOP!! This is what you DO NOT want to see! This retaining clip was inserted into the piston without the tool being seated properly and deeply enough into the piston! It will not retain the wrist pin, as it is not inserted into the groove in the piston! If left alone this engine would have failed within the first 30 seconds that it ran! Once the clip dislodges itself, the wrist pin would slide out, ruining the block, piston, rod, and likely the rest of the engine!
When this horrible instance occurs there is no way to remove the clip without it flying wildly inside the crankcase, requiring tear down to allow for removal of the clip. When this occurs, you are officially screwed!
Flashlights, mirrors, borescope, and tools with depth index are my friends during these processes...
This is what a properly seated wrist pin retaining clip looks like through the borescope. The components are dyed different colors before assembly so we can differentiate between them with the borescope. This clip installation is textbook perfect!
Wise assemblers will etch all their tools and use a pointer to orient the tools for proper clip insertion. This ensures that both the proper depth and clip orientation occur simultaneously. If these marks do not align the tool is not deep enough into the piston and the tool is not rotated correctly to insert the clip. Each and every bore size will have a different set of indices too!
No book or instructions will tell anyone to do these things. The Porsche assembly and tool instructions are worthless in this regard. It takes practice and common sense coupled to some Innovation to create these procedures. For the novice doing this for their first time, practicing many of these techniques prior to final assembly is a wise precaution.
Another shot of how we indexed the clip installation tool to ensure proper clip installation at each piston.
Cylinder #4 is a breeze to install the wrist pin and clip into place, since it's only 4" deep within the engine and most work can be done without the borescope. Once this piston is in, the work that takes all day to accomplish is behind us and it'll be smooth sailing until we set the cam timing.
Custom MLS head gasket shim used for adjusting and fine tuning of compression ratio with our larger bores and added stroke. We chose not to install these in this engine ecause we wanted an insanely high CR and very tight deck for this test engine, to push the limits. We believe in R&D - "Risk and Development".
Modified OE head gaskets opened up to accept the larger bore.
Partially assembled 2.9 engine with cylinder head 1-3 in place and ready for final torque... Note my improper tool usage with the Pliers being used to hold the timing chains. These timing chains are a PITA during assembly and you'll do whats necessary to keep them out of the way and free from binding during assembly. I'm sure there are lots of fancy and expensive tools from Porsche to help with this and other aspects, but as you can see, you don't need them.
Cylinder head after torquing with the lifter carrier in place and torqued, awaiting cam follower insertion.
Note the sealant under the head bolt... We made judicious use of many sealants throughout the engine, drawing from experience of building hundreds and hundreds of engines in the last decade alone.
Cam timing tools in place, camshaft drive and vario cam timing chains are in place and cam timing being set with the torquing of the 4 fasteners on the exhaust cam drive. Though this engine utilized stock camshafts they were reground and coated with PC11 to ensure optimal break-in with new followers. We also have adjusted the cam timing to make better use of the added 400ccs of displacement.
The *mostly complete* M96 2.9 Big Bore Flat Six Engine is now ready for the sump to be buttoned up.
Note the pickup tube spacer. This corrects the depth of the pickup with a deep sump and is included with LN Engineering's deep sump kit.
PC11 Coated Oil Pump gears await a dose of Vaseline to aid with oil system priming on initial start up, then they'll be covered by the oil pump cover after a new O ring is installed at the pump cover housing.
The Completed Flat 6 Innovations 2.9 Liter Big Bore Engine! (bottom view) Note the deep sump, spin-on oil filter adapter, and billet magnetic oil drain plug provided by LN Engineering.
Although not shown, now we'll add the ancillary components and subsystems and install the unit into the test car. We're sure you've seen this part already.
The below graphs show the before and after performance of our 2.5 to 2.9 engine.
Before and after. Rear wheel horsepower shown on a '99 Boxster Tiptronic. We apologize for the poor resolution of the graphs, as it is notoriously difficult to dyno a tiptronic as the transmission locks out the manual mode as soon as the front wheels aren't spinning!
Peak RWHP is up over 40HP and almost 50 Lb/ft of torque over the stock 2.5 Tip figures.
If this engine was in a manual car, we would expect approximately 12% additional RWHP based off our own dyno testing of a Tiptronic versus a manual gearbox.