06 May Adding Bump to Your Stick and Squish to Your Dish Part III
In Part I of our high performance engine building series, we looked at the process of tearing down an engine and some of the things to keep in mind along the way. In Part II, we looked at the process of inspecting and machining engine parts. As we continue with our high performance engine building series this month, we will look at the process of assembling the engine.
Assembling an engine is not simply a process of bolting the parts together once. You will need to trial assemble the engine several times in order to check clearances, especially when dealing with a high performance engine and non-stock parts. It is a time consuming process, and one that you do not want to rush. This is why the labour for professionally built engines can be so expensive.
It is also critically important that you spend a lot of time cleaning the parts, including using solvents, “pipe” or “riffle” brushes (for cleaning oil holes in the crankshaft, for example), compressed air to blow any remaining debris off of the parts, and then wrapping the clean parts until they are ready to install. Clean parts also mean a clean working environment, so ensure that your engine assembly workstation is equally spotless. Again, take your time and be thorough, as it will pay off in the long run with a longer service life.
Bottom End
As indicated last month, we decided to replace the rods with a set of “new” bead blasted, magnafluxed, clearanced, balanced, rebuilt VW rods, which came with heavy-duty rod bolts. The engine builder, Art Thraen (Aircooled Engineering) prefers rod balance within 1 gram, and these rods came perfectly balanced.
After thoroughly cleaning and carefully inspecting the rods (refer to photo #1), a new set of Kolbenschmidt bearings were installed, and the rods were installed on the crankshaft. The rod side play was then carefully measured (refer to photo #2). Art likes to see rod side play between .008″ and .016″. Our rods were within specification, averaging .013″. Too little clearance requires machining/sanding the rods. Art will not try to modify rods for use that have too much clearance, and will simply not use them. Art sets rod-to-bearing clearance at .002″.
Since we were converting from hydraulic lifters to solid lifters, a rebuilt set of original VW German lifters were ordered from Steve Long Racing (SLR) (refer to photo #3). The rebuild includes resurfacing the lifter face in order to ensure that the correct convex shape is attained. If it is not, the lifters will not spin when the camshaft lobes come into contact with the lifter face, which will rapidly increase lifter wear due to concentrating the wear in one location of the lifter face. Steve also parkerizes the lifter faces, which is a protective coating designed to reduce lifter wear.
The cause of accelerated camshaft and lifter wear in the past few years has been speculated by countless engine builders, attributed to everything from poorly matched surface hardness between the lifter and camshaft, the decrease in zinc content in oil over the last few years, too much spring pressure, too little spring pressure, incorrect lobe taper on camshafts, and incorrect break-in procedures. While it’s not the purpose of this series to examine the issue in great detail, Art has found a successful combination through using SLR reground VW lifters, followed by properly breaking-in the cam (more on that to follow). We’ll still pray to the Cam Gods, just in case.
After installing new Kolbenschmidt (standard) crankshaft bearings and Glyco cam bearings, the crankshaft was lowered into the case, followed by the cam. The specifications for the Engle FK8 cam are 298 degrees duration (258 degrees at .050″ lift), and .380″ lift on 108 lobe centres. This cam was chosen due to my experience driving other engines with similar combinations, and being impressed with the tremendous torque, power and drivability.
The camshaft was run “straight up,” (neither advanced nor retarded) and cam lube was smeared onto the cam lobes. Part of the trial assembly involved clearancing the camshaft in order to ensure that the rods do not hit the camshaft (refer to photo #5). You will also note that we elected to use stock helical cam gears. While many people prefer to convert to “straight cut” cam gears when using higher spring pressures in order to reduce cam bearing wear, in Art’s experience, stock gears are sufficient for the Erco dual valve springs that will be used. Using stock gears results in a quieter valve train and allows you to spend the money that would’ve been spent on straight cut gears on areas that will product more power, such as cylinder heads.
A thin coating of Curil T was applied to the case halves (refer to photo #6) prior to torquing the short block (refer to photo #7). Remember that the engine had already been trial-assembled several times to ensure that there were no issues during final assembly of the short block.
Lubrication
During the previous 80,000 kms, a 30 mm Melling oil pump had been used along with a Berg full-flow cover. Upon inspection, Art was not happy with the overall fit and tolerances in the oil pump, so he replaced it with a new Shadek 30 mm oil pump. The Berg full-flow cover was reused (refer to photo #8), which will push oil through a full flow oil filter.
Flywheel, Clutch and Pressure Plate
A new VW-forged, lightened, 12-pound flywheel was used, which will allow for quicker revs and reduce the amount of horsepower required to accelerate the engine in each gear due to less mass. In other words, free horsepower. After installing new main and flywheel seals, the use of a heavy-duty chromoly gland nut and large washer permitted torquing the flywheel to 390 ft./lbs. (refer to photo #9), ensuring that the flywheel will not come lose during occasional track use with radial tyres.
Despite the fact that the flywheel was new, Art still checked it to ensure that flywheel run-out was within spec. (refer to photo #10). Art likes to see no more than .006″ of run-out, and the flywheel was within specification at .003″. Excessive run-out will require resurfacing the flywheel by a machine shop.
The original KEP 1700 lb pressure plate was found to be in excellent shape and reused. After 80,000 kms, however, the stock sprung VW disc was showing significant wear in the rivets holding the springs to the center of the disc, which is common when using sprung discs in higher horsepower applications. It was replaced with a new solid (non-sprung) stock Fitchel and Sachs disc. The advantage of using a stock disc is that it is easier on the transmission due to its gentler engagement, yet should still be up to the job for this application (approximately 150 HP and occasional blasts down the ΒΌ mile track with radial tyres). The use of racing slicks at the track, however, may require a stronger disc due to their higher traction.
Top End
As indicated last month, the 90.5 mm Mahle pistons and cylinders were found to be in excellent shape. Due to the mileage, however, the cylinders were honed and new Deves piston rings were installed (refer to photo #11), with ring gaps set to .015″ (Art likes to set ring gaps between .012″ to .016″). New rings are an inexpensive investment, ensuring that you don’t encounter any compression loss or “blow-by” down the road.
Given Art’s (as well as others’) experience with the Engle FK8 cam, and the available fuel (US 91-94 octane), we decided to run 9:1 compression ratio. Trial assembling the top end resulted in .010″ deck height (refer to photo #12), which is insufficient clearance and would result in catastrophic engine damage. Art prefers to run at least .040″ deck height, modifying the cylinder head volume to achieve the desired compression ratio. By using .040″ copper head gaskets, resulting in .050″ deck height, and machining the cylinder head to reduce the chamber volume from 60 cc to 58 cc (refer to Part II of our series for more details), we ended up with 9:1 compression. The tight deck height should result in excellent combustion, reducing the chances of detonation often found when using large deck heights. The 9:1 compression ratio should also provide good fuel economy and horsepower.
The cylinder heads were installed, including using the stock cooling tin underneath the cylinders, followed by an adjustable push rod and original EMPI 1.4:1 rockers. After setting the rocker arm geometry and determining the correct push rod length, a set of heavy-duty aluminum pushrods from Aircooled.net were cut to length and installed, along with stock VW pushrod tubes. I prefer to use aluminum push rods in street engines as they are lighter and quieter than chromoly pushrods, and their heavy duty construction should have no problem standing up to Erco dual valve springs.
Art would have preferred to have converted the original EMPI rockers to bolt-together shafts, eliminating the use of clips. I’m a sucker for period speed parts however, and insisted that they remain unmodified. We compromised through Art safety wiring the clips to reduce the chance that they would come off during high RPM operation. Final lift at the valve was .468″ (refer to photo #13). The total lift, while relatively conservative, should result in longer valve spring life. If you were interested in more horsepower – and assuming that your heads flowed beyond that lift – different ratio rockers yielding higher lift could be used.
Initial Break-In
After filling the engine with thin oil (5w20 to ensure quick lubrication and GM Engine Oil Supplement with high zinc content to reduce the chance of “scuffing”), the rocker arms and spark plugs were removed and the engine was cranked on the engine stand to build oil pressure. This ensures full lubrication prior to initially firing the engine, and removing the rocker arms ensures that the lifters don’t wipe the break-in lube off of the cam, damaging the lifters and cam upon start up.
After reinstalling the spark plugs and rockers, as well as a distributor, wires, carburetors and an exhaust, the timing was set and the engine started (refer to photo #14). Engine revs were immediately brought to approximately 2,000 RPM. Never let the engine idle when breaking-in the cam, as insufficient lubrication occurs at low RPM to protect the lifters and cam while they are being surface-hardened during the first few critical minutes of operation. Art also prefers to vary the engine RPM during break-in as well, but keeps it within a few hundred RPM of 2,000.
The engine was run for 7 minutes, monitoring the head and oil temperatures. Because the engine was not under load, it does not overheat on the stand when run for short periods, despite not running cooling tin. The engine was inspected for oil leaks, and the oil was drained and inspected. It was then removed from the stand, all openings were tapped shut, and the entire long block was then wrapped in plastic in order to keep everything clean. The long block was then bolted and strapped to a wooden crate (refer to photo #15) and shipped cross-country for reinstallation into my ’67 Beetle.
In Part IV of the series, we’ll install the engine in the car and look at the before and after impact of the changes, both subjectively (how it feels) and objectively (performance numbers). We can’t wait to take this engine for a drive!
