1989 Pontiac Firebird Formula TPI Head Work - Rocking and Rolling

I have to say that with the way Blue Thunder now looks with its fat SLP wheel and tire combination, I don't worry about performance that much, at least until I see a fourth-gen. car go by. Then my competitive side comes out and the ideas begin to flow.

Most of the ideas will have to wait until we can see what we can do for cheap money. It's been the goal of this project since the beginning to find inexpensive horsepower upgrades and use them to make this pony car perform. With BT's suspension and wheel changes we not only ended up dropping quite a bit of money on the SLP wheels and Tokico suspension components, we compromised its drag strip weight transfer characteristics for better handling. The next round of mods was going to be simple, but hopefully effective.

Back in the July issue, we covered the installation and dyno testing of SLP's intake runners and JET Performance's underdrive pulley set. These two mods offered over 20 rear-wheel horsepower, bringing Blue Thunder's grand total to 236 horsepower and 303 lb.-ft. of torque. After getting the new suspension and wheel/tire package, Blue Thunder once again hit the drag strip with disappointing results.

The air was relatively cool, but the corrected altitude had other ideas. I made three runs with no improvement on my previous times. Run one started with a 2.16 short time and ended in 14.48 seconds at 94.28 mph. Run two was far worse but I blew the launch. A 14.67 resulted from the dismal 2.30 60-ft. time. Run three was the best of the day at 14.42. Trap speed improved to 95.31 and the 60-ft. was 2.18. It seems no amount of clutch slippage can get the car out quicker than 2.0-2.1 seconds. And I won't be sidestepping the left pedal with slicks to try to improve on that.

Our next track session proved to be far better. The air was around 900 feet below sea level with a 60-degree temperature, and the elapsed times showed it. The first run came in at 14.28 at 96.47 mph (2.14 60-ft.). Before we ran again, we checked the TPS voltage as we had not set it since SLP had fixed our roving sensor. I adjusted it to .68 with the throttle closed and 4.50 at WOT. Run two seemed to like the change as I finally improved on Blue Thunder's best ET with a 14.22 at 96.31 pass. Run number three was identical except for a slight difference in 60-ft. times (2.11 vs. 2.13).

What was most evident was that the mph was up on all three runs. This showed that BT was making the expected power. If I could get the 60-ft. time down in the 1.8-1.9 range, Blue Thunder would be where I want it to be, but getting that kind of reaction from the drivetrain would require more gear, more tire and a rear end that would hold up to some clutch drops. Personally, I don't feel like changing to slicks on a 13-14-second car and therefore will continue to get there without more tire or gear.

While conducting the LS1 vs. LT1 shootout, I found time to make a few runs and played with the ignition timing a little. MM&FF associate editor John Hedenburg worked the timing gun while I manned the distributor. According to the sticker under the hood, base timing was supposed to be set at 0 degrees, but we found Blue Thunder was already at 8. Since I didn't have all day to toy with the car, we only bumped the timing up once, to 15 degrees just to see what would happen. Well, when combined with the 29-30 degrees in the stock PROM program, that was 44 to 45 degrees total--way too much, and it turned up a goose egg. The throttle response was improved and the spark plugs were reading a little hot, but there was no improvement in elapsed time.

For the next round of mods, I chose one free one and three that would cost some coin. I had yet to port the upper plenum, which involved not only removing the casting ridges behind the throttle blades, but also opening up the sides of the plenum to match the siamese SLP runners. This I would do along with some new valvetrain components and an adjustable fuel pressure regulator. Although BT had never experienced any audible valve float, the stock 158,000-mile valve spring life had come up in numerous conversations and so I decided to throw on some fresh valve springs. While I was in there, it made sense to try some roller rockers as well. I also decided to upgrade the ratio from 1.5 to 1.6 for a little more airflow.

I called upon Competition Cams for both the new springs and the roller rockers. Part number 981-16 is a direct replacement spring that doesn't require any machining and uses the stock retainers and keepers. They feature a seat pressure of 105 pounds when installed at 1.700 inches, and an open pressure of 295 pounds at 1.250 inches.

I originally ordered a 1.6 ratio roller rocker, but a shipping mishap left us holding 1.52 ratio rockers instead. I went ahead and installed the Magnum rocker arms anyway since the valve covers were off. This would not give me the desired increase in lift, but it certainly couldn't hurt, plus I would get the added benefit of having the roller tips. The Comp Cams 1.52 Magnum rocker arms retail for $180.74, with the 1.60 ratio units going for $186.18. Also on the list was a fuel pressure regulator from TPI Specialties. Part no. 100-002 sells for $89 and includes the special Torx bit you'll need to remove and replace the units. The TPIS piece was easy to install, and offered rock solid fuel pressure adjustment.

For the installation, Blue Thunder headed back to Danny's Pro Performance in Keyport, NJ. Dan Garrity was put in charge of our valvetrain surgery, while DPP proprietor Dan Ryder took to hogging out the upper plenum. We spent a lengthy day installing the various components, and other time constraints prevented us from dyno testing the mods. The following day though, BT bolted to the track. Weather is a funny thing, except when you want to go fast and it pulls a 180 on you. As with most of the eastern United States, New Jersey has been receiving record amounts of rain this spring. This makes it rather difficult to schedule and keep track days, or even make the local street drags on Wednesday or Friday night. Our home track of Raceway Park in Englishtown, NJ has had 23 rainouts already (as I write this in June), so the weather hasn't been cooperating. At least when it was raining, the air was much cooler. When our track day came around, the clouds parted and we were blasted with 85-90 degree temperatures. Not to make excuses, but you just can't go fast when it's blistering hot out. Anyway, Blue Thunder hit the track with its newly ported intake manifold, roller rocker arms, fresh valve springs and the regulator. For the first run, I disconnected the brown spark output wire (located on the passenger side of the firewall) and set the base timing to 4 degrees. Fuel pressure was set at the stock 44 psi. Run number one started off badly with a 2.23 short time and concluded with a 14.54 at 95.20 mph. Despite the hot weather, mph only dropped off by one. For the second run, I bumped the timing from 4 to 8 degrees, and the car slowed to a 14.64 at 94.67 mph. My 60-ft. time was a 2.24, but since we were charting changes to timing and fuel pressure, keeping it consistent was slightly more important than going faster at this point.

For run number three, fuel pressure was bumped up to 46 psi. ET improved to a 14.58 (2.23 short time), but mph dropped to a 93.01. I dialed back the fuel pressure this time to 42, which was where the regulator seemed to bottom out. This tactic netted the best run so far at a 14.50 (2.24 60-ft.) at 95.34 mph. As you can see, the mph went back up which was what I was hoping for. I had iced the intake for all of these runs, but these were not the results I was anticipating. My last pass of the day, I made no changes but cut the short time to 2.19 seconds and crossed the stripe in 14.48 at 95.8 mph. Considering it was some 20 degrees warmer than the last time I ran the car, the results were somewhat respectable.

At this point it looks as though I will have to do one of three things to get the car into the 13s. One idea would be to put the car on a severe diet. It only weighs 3,500 with me in it and I really don't want to lose any of my creature comforts so that idea is kind of out. I could wait for cool weather to come back, but that may be another six months. The only other option is to throw more parts at it. I still have a good chunk of my budget to spend so I'll be looking into a few things. If you would like to see something tested, or want Blue Thunder to take a particular direction, drop me a line at steve.baur@primedia.com. Questions or comments are also welcome.

The rockers come with their own hardware to fasten them to the heads.	Adjustment procedure may differ from year to year. Ours started by tightening the valves to zero lash, or just enough to spin the pushrod with your fingers. Start with exhaust 1, 3, 4, 8 and intake 1, 2, 5, and 7 with the engine in position to fire the number one cylinder. Then, we turned the motor over one complete revolution so it was on number 6. Then we adjusted exhaust 2, 5, 6, 7 and intake 3, 4, 6, 8. Then you only need to warm up the engine and adjust them until they are all quiet.	Here you can see the ridge that we are removing. It's not exactly designed for optimum airflow from the factory.
At the top of the photo, you can see there is some room for improvement on the side of the plenum also. Just be careful not to grind through to the other side.	Here is our almost-finished plenum with both sides and both ridges smoothed out.	We also wanted to siamese the sides of the plenum to match the SLP runners.
Here, Dan reassembles the TPI upper plenum. Now it's off to the track.	We saw good results by having the TPS sensor dialed in. Unlike Mustangs, TPI cars seem to respond better to stock or close to stock settings.