Project Rally Saab 99 | Magazine Series Part 6: Preparing for Rally Tennessee in Only Three Months

Photography by Per Schroeder

[Editor's Note: This article originally ran in the August 2008 issue of Grassroots Motorsports; for more updates, visit here.]

 

Our debut stage rally event with our 1977 Saab 99 went well. The car successfully completed the competition, drove onto the trailer under its own power, and didn’t display any banged-up sheet metal. On the negative side, the car wasn’t exactly setting any speed records.

We had about three months to get the 99 ready for Rally Tennessee, so we started to tackle our to-do list. The major improvements included rebuilding the engine and installing a limited-slip differential. We also had a host of other smaller projects planned. 

Although we did have those three months, we had a lot of work to do. Making matters even more interesting was the fact that the Susquehannock Trail Performance Rally was scheduled for two weeks after Tennessee. The season was upon us.

More Power, Cap’n!

While our performance at Sandblast was satisfactory—that is, we finished—we weren’t entirely happy with the car’s speed. In fact, the Saab was quite slow in a straight line. 

Baseline chassis dynamometer numbers revealed that we were putting merely 82 horsepower to the wheels. For an engine that was originally rated at 115 horsepower at the crank, that reading was quite low. A compression test revealed that three of the cylinders generated 150 psi and one was at 130—quite a bit less than the factory spec of 175 psi. 

Clearly the Saab’s engine was tired, meaning it was time for a rebuild. While we were in there, we decided to coax more power out through some simple modifications. Our goal was to gain some torque and horsepower throughout the rpm range without sacrificing reliability. 

We ran our first event in NASA’s Stock category, but we felt that this class really limited the car’s potential. We decided to move up to the M2 class, the equivalent of Rally America’s G2 classification. This is essentially a no-holds-barred class for normally aspirated, small-displacement, two-wheel-drive cars. We are, however, keeping our preparation to period-correct tweaks so that if and when there’s a healthy Historic class, we can run there as well. 

For engine parts, we contacted Jack Lawrence at Motor Sport Service (MSS). He hooked us up with the proper bearings, gaskets and pistons—the latter being cast flat top pistons from a 2.0-liter Ford Pinto. These pistons wound up giving us approximately 0.030-inch overbore and bumped our compression ratio from 8.3:1 to about 10:1. 

To make the Pinto pistons work in our Saab, we had to machine a groove to secure the wrist pins’ circlips and also machine the pistons’ skirt area to clear the counterweights on the crank. Despite this additional machining, the Ford pistons are a cheap way to get a good bump in compression—they wind up being about $90 apiece.

The head on a Saab B-series engine is very lopsided, with a great intake tract but a limited exhaust path. We left the intake ports alone, but decided that some work with a die grinder and Dremel on the exhaust side wouldn’t hurt things a bit. 

We cleaned up the pocket area of the exhaust ports and smoothed out the transition from the valve guide area into the port itself, finally matching it to the exhaust manifold gasket. While a properly ported head should ideally be worked over with the help of a flow bench, a little home porting can do some good without costing any money. 

After the porting was complete, we took it back to the machine shop for more work. The guys there decked the head 0.007-inch to clean up the surface, installed new valve guides and performed a three-angle valve job.

Jack at MSS also supplied us with one of his $190 street performance camshafts. This cam is said to have a solid powerband from 3000 to 7500 rpm. We purchased the recommended dual valve springs to help curtail valve float at the upper reaches of the tachometer. 

After welding in some crossmember reinforcements, we repainted our engine bay and added some beefier Vorshlag engine mounts to handle the additional torque of our new engine and transmission. Among other things, the new setup features higher compression pistons, a limited slip differential and head porting.

With our engine out and parts ordered, we had some time on our hands before the work could continue. We used the time to reinforce the engine compartment and add a coat of paint to make it look as good as the exterior. The first step was to give the entire area a thorough degreasing, which we followed up with a dose of wire wheel action using our angle grinder. 

We welded in reinforcements to the upper control arm mounting points and the lower subframe that runs under the transmission. The goal was to prevent flexing over larger bumps and to provide that last little bit of impact protection for our fragile, low-hanging transmission. Once that was completed, we primed the entire engine bay and painted it the original Antelope Brown color. Next we installed a different steering rack, this one from a 99 EMS that had a quicker ratio. This will make some of the twistier turns easier to handle. 

When all of our engine bits came in and our block and crank were back from the machine shop, it was time for some assembly work. The long block was assembled over the course of a Saturday, and the work went very smoothly. We used Red Line Oil assembly lube to give the bearings and camshaft lobe surfaces a good greasing for the initial startup, then simply followed our service manual for torque specs. 

We installed a lightened MSS flywheel along with our previously used Centerforce clutch—which, by the way, was still functioning beautifully. The MSS flywheel was five pounds lighter than stock, enough to make a noticeable improvement in throttle response and acceleration. 

All told, we spent about $1100 in parts on the long block rebuild, including the performance camshaft and the lightened flywheel. We spent another $700 in machine work. That tracks pretty comparably with just about every other four-cylinder engine we’ve rebuilt, from Alfa to Volvo. 

Once the new engine is broken in, we’ll take it to a dyno for tuning. Look for those numbers in the next installment. 

We started the engine rebuilding process by pulling the drivetrain out of the rally car and stripping the engine down to its bare essentials. We then delivered the crank, rods, head and block to our local machine shop to have them looked over. Ken Jack at Fas-Trac checked the head for warp, disassembled the valve train and handed the head back to us for porting. 

The block and crank were also checked for condition, and we were told that we could regrind the crank for 0.010-inch oversized bearings and 0.020-inch overbore on the pistons. That was good news, since it basically meant that our engine didn’t require much fancy work to get back up to snuff.

Grip the Wheel

Our first rally highlighted how much the car needed a limited-slip differential. Unfortunately, performance differentials for the Saab 99 and 900 are few and far between.

Quaife used to make a unit that would fit our car, but these are hard to find on the used market and are not really appropriate for rally use—they don’t function well when one tire is off the ground. Welding the differential solid was another option, but not a good one. That fix would only work on very loose surfaces, meaning it wouldn’t be the hot setup for tarmac rallies.

Fortunately we found a solution: The folks at SaabRally.com set up a group buy of 10 performance differentials from Gripper, a U.K.-based company. The Gripper is a 1.5-way clutch-type limited-slip that allows for less lockup on deceleration to help the car turn. The unit then locks up very solidly on corner exit for maximum traction. The group buy deal netted us an awesome performance differential for about $1000, including shipping and tariffs. 

We installed the Gripper differential in a used but good five-speed transmission from a mid-’80s Saab 900. The fifth gear isn’t at all crucial for rally work, but it does make the transit stages a lot more bearable. 

Wrap It Up

The engine and transmission were then hoisted into the car while we worked on getting everything hooked up. Saab engine mounts are dimensionally identical to those in an E30-chassis BMW, so we went with a pair of polyurethane mounts from Vorshlag. The rest of the reassembly work was straightforward: We just needed to make a few tweaks to the shifter since we now had an additional forward gear. 

For an exhaust system, the no-name pea shooter special that the car came with was not going to cut it. Our original deal on the car came with a well-used MSS race header which would be a great replacement for the factory cast-iron manifold. We cleaned the header, shot it with some paint, and then blanketed it with DEI’s header wrap to keep the engine compartment from becoming an oven. 

We installed header wrap and plug boots from DEI to keep underhood temperatures in check as we blast through the stages.

The spark plug wires on a Saab engine are routed perilously close to the exhaust header, so we added a quartet of spark plug boots from DEI. After the header, we fabricated a 2.25-inch exhaust with a MagnaFlow muffler. The result is a purposeful growl that only becomes aggressive at full throttle. 

Tahrs and Bahrs for Them Thar Hills

Rally Tennessee is held on some seriously twisty asphalt roads around Linden, so we needed to look at our tire situation. Our Michelin gravel rally tires and BFGoodrich Traction T/A street tires really wouldn’t hold up for an event like this, so we ordered a set of 15x7-inch, 30mm-offset Superlite wheels from VTO Performance. These wheels have an MGB-like 4x114.3 bolt pattern. For tires, we went with the 205/50R15 Toyo Proxes RA-1 at full tread depth. 

A rally car’s suspension is asked to handle a lot, from near-Baja roughness to smooth asphalt. Since our Saab was initially set up for gravel terrain, we needed to figure out a plan of attack for tarmac. The car originally came without any anti-roll bars, and on top of that, we were using taller rally springs—clearly not a great setup for higher-grip surfaces. We decided to keep the springs in place and simply supplement their rates with a pair of Addco anti-roll bars. 

The bars measure 7/8-inch thick and are a time- and cost-effective way to reduce body roll. An added bonus is that we can quickly remove them from the car for the following event, the Susquehannock Trail Performance Rally, which features gravel at its roughest. The Addco bars can be found online for about $130 apiece. 

A Hundred Little Details

With the basics handled, our Saab was back on the road. That didn’t mean we were ready for our next event, however; it just allowed us to start a whole new set of tasks aimed at making the car more usable and reliable than ever. 

We set to work on our new list, which included cleaning up wiring, flocking the dash’s top with a DonJer Products kit, reinforcing the fuel cell mounting straps and installing some hood tie-down straps. We’ve documented these upgrades (and many more) on our project car pages at grassrootsmotorsports.com. 

And our looming deadline? We finished the work with a few weeks to spare, allowing us some shakedown time on the streets and at local autocrosses. Look for updates online and wish us luck.

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