How to Build a Street/Strip 350

STRIP TALES

The above details ate up the day we had planned for the nitrous installation, so our first shot at the dragstrip had to be without the fast gas. After an hour drive to California Speedway in Fontana, California, we mounted our budget, 26x8x15 DOT Mickey Thompson ET Street tires and headed to the starting line. Our first attempt was going to be a soft launch by rolling in on the throttle and shifting at 5,800 rpm. The tires didn’t spin, but the car felt soft on the launch, which only added to our surprise when the Compulink timers spit out a 12.90-at-105.01-mph pass. The 60-foot time was indeed slow at 1.98, but we were genuinely surprised at the 12-second e.t. We then spent the next five runs trying to replicate the first one, as the car experienced a huge hesitation whenever we tried to nail the throttle on the starting line. A wide-ranging series of tuning efforts failed to produce significant improvements, and we settled for rolling in the throttle to produce our best pass of the day with a 12.86 at 105.64 mph.

After our first dragstrip session with a brand-new engine, it was obvious our hesitation problem was related to a serious lean condition caused when all four barrels of the Holley Street HP carburetor were simultaneously slammed open. It seemed we needed more fuel. We tried using the stock pink accelerator pump cams in the No. 1 position and increasing the secondary squirter size up to a 50, but even with these changes, we still had a major hesitation that would not go away. Our swap-meet carburetor had a major flaw (which is probably why it was cheap), so we switched to a 750-cfm vacuum-secondary carburetor that immediately eliminated the starting line bog. We were now ready to go back to the track.

Now that the car was able to generate a decent launch normally aspirated, we were ready to hit it with the nitrous. On the dyno, we had merely retarded the initial timing to compensate for the nitrous, but we needed something more sophisticated on the dragstrip. This called for an MSD 6AL-2 box. This digital CD controller/amplifier offers the luxury of digitally programming the ignition-advance and nitrous-retard functions via a laptop. This can be done with an add-on retard box and an MSD 6AL, but we liked the idea that for only a few more bucks, we could have a 6AL-2 digital control. The digital curve gives us the freedom to add more timing at low speed and then flatten or even lower the timing at higher rpm. The 6AL-2 offers burnout and launch rpm control, but our focus was on the single retard function that we would use when the nitrous is triggered.

When using the MSD digital control over the standard mechanical advance, the first thing to do is lock out the distributor’s advance curve and set the maximum advance with the initial- timing setting. The MSD box then retards the timing back from that setting to your maximum advance spec. For example, we set the initial timing at 40 degrees and then dialed in the curve with a total of 36 degrees for the normally aspirated runs. We used a GM large cap HEI originally used on EFI engines, which has no advance mechanism. Alternatively, we could have used any MSD distributor. The MSD units feature a simple relocation of the advance pin that locks out the advance. We used the factory distributor because it was cheap, and we adapted it to the MSD-6AL-2.

Because we were making more power now with the better heads, we decided to start with the 150hp nitrous tune-up (0.063 jets for both nitrous and fuel). We also opted for the most conservative NOS timing recommendation of 25 degrees.

Due to a minor trans leak that required a short stay at California Performance Transmission, we only had time to mount the MSD and the nitrous system, which we unfortunately wired into the car with a little too much haste. Worse yet, we did not have time to test it before going to the track. Can you guess what happened next?