Numerous books have been written on the subject of engine assembly, and since this is a general information article, we won't attempt to cover all the details; source your reference material for the particulars. However, there are some basic tips and techniques that apply to most engines.By now the block should be cleaned, dried, and mounted on a suitable stand. All fasteners to be used should have also been completely cleaned, and all threads free of burrs. Have quality assembly lube on hand-this stuff is preferred to regular engine oil for its ability to stick to the parts it's applied to rather than running off into the oil pan prior to the initial start-up.
If the machine shop has done a good job, there should be no concerns over bearing clearances at this point, but it's always a good idea to check. The novice builder is unlikely to have a set of micrometers, but inexpensive Plastigage is cheap insurance that's available at most good auto parts stores and machine shops.
For most American engines from the '50s up into the '90s, the only specialty tools needed for assembly are a torque wrench, a ring compressor, and possibly a harmonic-balancer installer.
Use plenty of assembly lube on the bearings and make sure that all fasteners that don't require sealant are coated with a few drops of engine oil on the threads and under the shoulders. Dry threads can create inaccurate torque readings. Piston rings should also be treated with a thin coat of oil before being installed on the pistons, and the rod bolts should be covered-a short piece of rubber hose works-to ensure that they don't scratch the crank during installation. Continue to spin-test the rotating assembly after torquing each rod to make sure there is no binding. Check main- and rod-bearing clearances, crank endplay, and rod side clearance as specified by the manufacturer. Crankshaft end seals (rear main and timing cover) should also be coated with engine oil.
When it comes time to install the cylinder heads, make sure to follow the torque sequence listed in the factory manual, and work up to the final torque by following the sequence in three steps ( for example, 25 lb-ft, 50 lb-ft, and then 75 lb-ft). Intake manifolds usually have a factory-prescribed torque sequence as well. Procedures for valve adjustment should be found in your source books, but if the only instructions are for assembled, running engines, try consulting the camshaft manufacturer-most have tech lines and Web sites.
Our 350 went together without incident, though at one point we did notice that the crank suddenly felt as if it didn't want to turn. A quick check revealed a misplaced main cap, the result of a very faint position stamp that we misread. Fortunately, since we were spin-testing frequently, the mistake was quickly discovered. We worked smoothly and steadily, starting with the crank, then the piston/rod assemblies, followed by the cam and timing set. We topped off the bottom end with a fresh stock oil pump before buttoning up the timing cover and oil pan, and then flipped the block over to install the heads, valvetrain, and intake. All in all, it was a full afternoon's work, but we'd done it before. Take all the time you need-it's not a race...yet.
Most completed first engines will go from the stand to the car (see "Starting a New Engine" in this issue for more on that), but we wanted to dyno-test our spare-parts mule to see how well it would run before installing it. Our standard-bore, flattop piston 350 was capped with a set of cast-iron Chevy Vortec heads featuring stock 1.94/1.50-inch valves and 64cc chambers. We used Fel-Pro steel shim head gaskets to get as much compression as possible (around 9.4:1) and installed a Crane PowerMax H-278-2 cam kit with 0.467/0.494-inch lift and 222/234 degrees duration on a 114-degree lobe separation angle. An Edelbrock Performer RPM Air Gap intake matched our goals of a smooth-running yet potent street engine. We dressed the engine with GM Performance Parts center-bolt valve covers and installed a Speed Demon 750-cfm carb and MSD distributor just after filling the crankcase with Union 76 Racing motor oil and priming the oiling system.
The fresh engine fired right up and instantly displayed strong oil pressure. The first order of business was to break in the cam at around 2,000 rpm for roughly 15 minutes. After the break-in lube was replaced with fresh oil, we made a series of power pulls, and found that the combination needed very little tuning. With 34 degrees total timing, our low-buck 350 made 404 hp at 5,600 rpm, and 428 lb-ft of torque at 4,400. The torque curve was very flat, showing 400 lb-ft at 3,000 rpm where the pulls began and maintaining 380 lb-ft at the horsepower peak. This very basic combination proves that a well-planned combination can yield excellent results, even when the biggest, baddest parts are left on the shelf. Just think how good that 400 hp and 425 lb-ft, combined with a sense of accomplishment, would feel during that first testdrive. CCOur low-buck 350 made 404 hp at 5,600 rpm, and 428 lb-ft of torque at 4,400. The torque curve was very flat, showing 400 lb-ft at 3,000 rpm where the pulls began and maintaining 380 lb-ft at the horsepower peak.
530 Fentress Blvd.
2700 California St.
26555 Northwestern Hwy.
Dougan's Rebuilding & Machine Shop