Stock-Block 535HP Screamer - D.S.S. Engine Build

After the carb went on, the headers were installed so as to allow a plug cable routing that best clears the ultimately hot pipes. From here, it's just a question of routing the plug cables in the neatest manner possible. As far as plug-cable routing goes, our project engines need to look good as well as perform. As of late, a completely different strategy has been used since ACCEL introduced its 10.8mm sheathed cables. Normally on our engine builds, a cable support system would be used for looks and to separate the cables so that big plug gap wouldn't cause voltage to cross-fire from one cable to another. The extra 1mm wall thickness of the 10.8 mm cable over the 8.8 offers more insulation than 1/4 inch of air gap. What this means is that the cables can now be bundled and tie-wraps used to hold them in place. This greatly simplifies wiring up a functional system, and it looks really good too. With the plug cables done, our 331 D.S.S.. track-day engine is looking good and ready to ride our DTS dyno.

Dyno Time
The nice thing about having an engine cart-style dyno like a DTS is that you can load the engine on the cart outside of the cell, wheel it in, and hook it up in a couple of minutes. With the timing set to 32 degrees (total advance), we gave the 331 a two-hour break-in on Castrol GTX.

After a post break-in service using Joe Gibbs racing oil (roller grade as used in their Busch cars), the first exploratory pulls were made. Two things were quickly learned. One was that the engine was quite fussy over the plugs it liked best, and that the carb calibration required for this small-block Ford was way different than the last engine on which it was run (393-inch street Windsor). What started off looking a little disappointing ended up as a "Wow-we may have too much power."

Getting to this point took not only carb jetting and ignition tuning, but also plug selection and secondary (collector) exhaust lengths. When we first hit the dyno, our 331 could only muster some 400 lb-ft of torque along with 420 horses. The jetting and ignition were no surprise, but the sensitivity to plugs was. We ended up with Autolite 3922s.

Our dyno headers are made by Kooks Headers of Bay Shore, New York. We use these for at least two reasons. First, they're extremely well made. Second, they're good for output. Our engine made its best overall curves when the secondary pipes were adjusted to 14 inches from the exit end of the four merged primary pipes. So how sensitive was it? Way more than we usually see. Just a 3-inch change showed as much as an 18hp difference.

As for the power, the two days spent on the dyno proved worthwhile. Because of the big cam, output much under 3,500 rpm was hardly sensational. As for idle, the lowest rpm with any kind of smoothness was about 1,050. When the dyno tach hit 4,000, you could hear this engine come alive. As you can see from the graph, we stopped testing at 7,300 rpm, and it looked as if that was still a couple of hundred rpm short of peak output. The reason for stopping short is that this D.S.S. unit was making more power than anticipated and, though it was selected, it was still nonetheless a stock-block.

An educated guess here is that, on the track, the best shift point would have been about 8,000 rpm. This poses the question of just how long the block would last. From the graph, it looks as if the power is still climbing to the extent that the 540 figure may have been surpassed. As for torque, a peak number of 442 lb-ft was seen, and that's a pretty respectable figure for a 10.4:1 331-inch engine. As for having too much power, we had an instant fix-a 7,000-rpm chip for the rev limiter.

Clearly this 331 was capable of making power to the extent that it deserved a significantly better block such as those made by Dart, Ford Racing Performance Parts, or World Products. If the budget had been about $1,200 more, that would've been the way to go. Not only would this have delivered the extra block strength needed, but also the fact that a bigger bore for 358 cubes could have been used. Even on pump gas, such a combination could well have yielded some 590 hp along with an 8,000-rpm redline.