While I was putting the finishing touches on the cylinder deflector install, Becker was mating the cylinder heads onto the cam towers, once again utilizing Three Bond 1104 liquid gasket instead of the factory recommended Loctite 574. The heads and cam towers were mounted as a unit (holding the oil return tubes in place) onto each bank of cylinders. After the head stud threads were treated with ARP's special assembly lube, I installed the washers and torqued the 12-point head nuts using a cross pattern technique. The new Web-Cam camshafts were installed into the cam towers and lubricated with Web-Cam's assembly lube. I mounted the now pressure-tested and ultrasonically cleaned oil cooler at the front of the engine next, and Becker installed the chain boxes and the cam end cover plates (with new o-ring and gasket from the gasket set), and tightened the three cam end plate retaining bolts on each bank. He and I then each took one side of the motor, fitting the thrust spacers, spacer shims, woodruff keys and cam sprocket flanges.

The cam sprockets were properly oriented before hanging the dual timing chains and sliding them into place. The cam sprockets are identical left to right, but the dished surface faces the pulley end on the left bank and the flywheel side on the right. It is also wise to make sure the camshaft sprockets run parallel with the intermediate shaft sprockets to minimize wear of the timing chain and related components. The last two black chain ramps were finally fitted along with the idler sprocket assemblies. A special tool is used to keep tension on the chains during this step on a 911 engine assembly, as the oil pressure-fed chain tensioners should not be installed until after the cam timing has been set. The large cam bolts should only be tightened by hand at this point, as they will be removed again later so the cams can be properly timed.

The rocker arms and shafts for cylinders #1 and #4 were ready to be installed in order to carefully check the piston-to-valve clearance. This step is overlooked by many but should be performed by all, especially if new pistons and/or camshafts are being installed. The intake and exhaust valve clearance is adjusted to 0.004-inch (or 0.102mm as measured the European way). Remember to check that the motor is at TDC for cylinder #1. Web-Cam recommended a minimum clearance of 0.050-inch on the intake side and 0.080-inch on the exhaust side for the 20/21 cam profile. In this assembly, the piston-to-valve clearance is a non-issue as the high-dome pistons used in this particular application are generally used in conjunction with much higher lift and longer duration camshafts. The Web-Cam 20/21 grind is one of the hottest profiles available for use with the standard CIS/Motronic piston dome configuration, where the clearance can be awfully tight, but with the larger valve relief of these RSR high-dome pistons, the clearance is easily over 0.080-inch. To check the clearance, simply remove the retaining nut on the valve adjustment screw and turn the screw until it touches the tip of the valve. The M8x1 screw will open the valve 0.040-inch or 1mm for every full 360-degree turn. Simply count the number of turns until the valve rests against the piston. The process was then repeated for cylinder #4. If the minimum clearance is not attained, you must stop immediately and address the problem before continuing with the rebuild.

Timing the camshafts is a very important process that must be done correctly in order to have a motor that makes the most power possible. The camshafts are literally the heart of the motor and determine the engine's personality. The complete timing procedure is much too in-depth to discuss in this article, but trust me when I tell you these cams were properly timed at 2.0mm overlap and well within Web-Cam's specified range of 1.9mm-2.2mm for the 20/21 profile. Once the settings were verified on both banks, the large cam bolts were torqued down to an incredible 90 ft-lb. The remaining rocker arms and shafts (with new RSR seals now riding in their grooves) were installed and the valve clearances adjusted.

After I removed Becker's special chain tensioning tool and installed the oil pressure-fed chain tensioners, the chain housing covers and valve covers were placed into position with new gaskets. The cam oil lines, oil temperature, and oil pressure senders were the last components to be fitted on the motor before the long block was ready to accept the intake, exhaust, and electrical components. It looks like a 911 motor again!

While Becker and I are nearing completion of the motor, Dwain Dement and the guys at Vision Motorsports are hard at work prepping the chassis with some final tweaks in anticipation of reinstallation. Next time we'll wrap up the assembly by installing the intake, exhaust and electrical components needed to finish the rebuild and fire up this beast. Vision lead tech Mike Olsen will guide us through the motor installation into the chassis and the proper break-in procedure after initial start-up. The engine mapping wizardry of Steve Wong at 911chips will optimize the fuel and timing curves to unleash the 3.5L motor's full potential. Finally, we'll come full circle and return to the Dynojet 248C to measure the improvements made over the original 3.2L output.

RECOMMENDED READING


Robert Bentley Service Manual,
1984-1989 Porsche 911 Carrera

Bentley Publishers
www.BentleyPublishers.com

How to Rebuild & Modify Porsche 911 Engines
by Wayne Dempsey
Motorbooks International
www.pelicanparts.com

SOURCE
B. Precise SSF Imported Auto Parts
466 Forbes Rd.
South San Francisco
CA  94080
Specialized Coatings
5862 Research Dr
Huntington Beach
CA  92649
Wrightwood Racing
1401 Vanguard Dr.
Oxnard
CA  93033
By Ralph B Hollack
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