DAMON JURKIEWICZ
Industrial Design
PROJECT BUG 3.0
There's nothing more tragic than an empty engine compartment. Follow along as I build a 2332CC fuel injected turbocharged dry sump engine for this 1958 VW Bug.
Some of the parts we will be working with. Aside from the distributor drive gear and gear spacer there isn't much if any Volkswagen content in this engine. Even the case is from a domestic manufacturer. For where we are headed a stock case really isn't an option anymore.
We begin this process by washing EVERYTHING until it's clean... Then we wash it again. This is a domestically forged 84MM FAA aircraft use approved chromalloy crankshaft. Unlike the stock gland nut and dowel arrangement, this crank has a large flywheel flange, six bolts and six large dowel pins holding on the flywheel. The crank also features 2" diameter narrow Chevy journals for the rods and has a BMW oversized center main journal for greatly increased crank rigidity.
Our first machining operation. We are modifying the case to take a BMW bearing on the center main. This requires carefully locating, aligning and notching the center main journal. This has to be done on both the left and right side of the case. Done wrong this is a quick way to ruin a $1500 case!
Main bearings are installed, I am now checking the fit of the camshaft, camshaft bearings and lifters. In my hand is a modified lifter, the small notch between the two oiling bands greatly increases oil flow to the valve train through lifter oil circuit. Oil is more than just lubrication, it also carries away heat from every thing it touches. On a turbocharged air cooled engine a large reservoir of cool oil is the first line of defense for overheating due to its thermal capacitance.
First steps in assembling the cam gear, spacer and distributor drive gear on the crankshaft. We actually heat all the components in good old 5W30 on the stove in a stainless steel sauce pan. This grows the parts a few thousandths of an inch so we can drop them over the nose of the crank and align them more easily. These parts are a shrink fit requiring a press to disassemble them!
Even with heating you still need to drive everything home with a 20 ton press and a steel driving sleeve.
This is a shot of the assembled crank and cam in the engine case. The close up shows just how much crankshaft we have stuffed in the case. Things are really tight. As a rule it is best to maintain a running clearance of no less than .040" on components in the rotating or reciprocating assembly.
In this slide I am notching a set of incredibly expensive Carrillo rods with Pauter style oil squirters. The purpose of these groves is to spray high pressure oil from the crank journals at the back sides of the pistons to provide cooling and positive pin oiling. This lowers piston temperatures and helps prevent detonation.
I am deburring and burnishing the sides of the rods in these pictures. The rods will need to be rebalanced after performing this operation because material has been removed. Typically in a performance engine we try to be within + /- .5 gram on rod balancing for all four rods.
Shown here is the process of checking bearing clearances. This is done for rods and mains as well. I usually zero my reading on the bearing bore and compare it to the journal using a micrometer. If a bearing is tight there are two options, grind the crank... not optimal... or try some other sets of bearings. Due to manufacturing variation between brands it is some times possible to adjust clearances simply by trying other bearings. You can also find +/- bearing sets as well.
After sizing bearings it's time to install the rods and torque them to their specific bolt stretch point. Then we measure the side gap on either side of the rod journal. In this case we find that it is .008". For a hot running turbo engine up to .010" is fine. It is a enough gap to maintain oil pressure but it gives good oil flow through the bearings to provide plenty of cooling while reducing the possibility of seizing due to thermal expansion and contraction. (yes it really happens on hot air cooled engines)
Adding pistons. Hands down, Wiseco has the best off the shelf air cooled Volkswagen pistons available today. Indestructible forgings, graphite skirts, modern nitrided rings, tool steel wrist pins. Eventually the faces of these pistons will be coated with a thermal barrier coating to reduce piston temperatures and prevent detonation.
Before things go any further we do a quick test fitting of the pistons, cylinders and heads to see how things fit. The cylinders will need a lot of shortening but the inside and outside bore diameters all seem to match up with the correct clearances. Rings will be gapped later.
Unlike your knuckle dragging V8 or your Honda, the VW engine is highly modular in design allowing the engine builder to easily alter bore, stroke, rod length or deck height. In this slide I am setting top dead center with a dial indicator and a torque plate. Next I measure the depth of the piston in the bore. We are building a "Zero Deck" engine using a .040" thick copper head gasket to get optimal quench characteristics and reduce the potential for detonation. To do this the cylinder head chambers are cut to a very specific volume giving us our target compression ratio which is going to be 9.5:1 on this turbo engine.
To do this job accurately and safely you need a big ass lathe... This is a 94MM bore cylinder being cut on a big ass lathe with a big ass chuck and a big ass live center. A digital read out is also HUGELY important. A bed stop will get you close, the digital read out will get you perfect. All four sets need to be EXACTLY the same length.
Another test fit after machining all four cylinders. You might notice the enormous intake passages feeding the 44MM intake valves on these heads. A stock intake valve is only 35.5MM! The new exhaust valves are bigger than that! Also notice the blue Pauter machine 1.3:1 roller rocker assembly and titanium spring retainers.
Looking ahead a bit. This is a twin disc setup provided by Kennedy Engineering in California. It uses a stage 2 pressure plate, a tool steel float plate, a highly modified lightened forged chromoly flywheel and a pair of sintered puck reduced diameter clutch plates. Since we are targeting 400+ horsepower for this engine I thought it would be a good idea to go this route rather than destroying by engine thrust bearings with a stage 4 clutch pressure plate. That said I'm afraid of this clutch. It's a binary system.
Check back soon for more mechanical mayhem!
Updated 4-17-2014