Wild engines, with aluminum everything, mega cubic inches, huge superchargers, three stages of nitrous, and untold horsepower are fascinating, but back in the real world, most of us live with much more modest combos. Stock or near-stock engines have to work well on the street, and that means starting in a variety of weather, not overheating, idling at a reasonable rpm, and working with power accessories.
Speaking of power, more is always better, right? The vintage muscle cars have a lot of power in stock form, but what if your prized Pontiac could run like a Pure Stock Drags racer? You might be surprised to find that tuning for the dragstrip works very well on the street, too. It's all about getting the engine to move as much air as possible, and burn fuel efficiently.
Nearly nobody else we know has the depth of experience or consistent results as Dan Jensen, life-long Pontiac guy, founder of the Pure Stock Drags, and full-time restorer and engine builder. We spent some quality time with him to discuss one of his favorite topics – Pontiacs, and how to make them really run.
If this easily overlooked servo isn’t working, you could be choking your engine and breath
Here's a clever trick that costs less than $5 and gives you free horsepower. Take a length of simple vacuum hose or rubber fuel line, wrap it in a circle equal to the diameter of the air filter, and hold it with a double-male fitting. Put it on top of or under the filter element. This raises the lid of the breather, opening up a lot of new area for the engine to breathe through. Raising the lid just 1/4 inch is all you need, and it looks stock, too. This makes a big difference in your engine's ability to flow air, especially if it has a single-snorkel breather.
Breathers may also conceal a big, but almost always overlooked, power robber. Late '60s-and-up Pontiacs had a vacuum-operated system that drew intake air from around the exhaust manifold—the first part to heat up once the engine starts—at cold start, to speed warm-up and prevent carburetor icing during very cold weather. A pre-heater flap built into the breather's snorkel closes off the snorkel opening and instead pulls in air from around the exhaust manifold. Once the engine warms up, a temperature sensor inside the breather sends vacuum to a canister on the snorkel, and the diverter opens the snorkel—if the system is working right. If not, your engine is breathing very hot air, and a lot less than it needs.
On the topic of air filters, Dan says the dyno results are clear. "We saw no difference between a reusable air filter and a clean, stock paper filter."
Dan's tip: Raising the [breather] lid [as explained] can be good for anywhere from 6 to 10 horsepower on Pontiac V-8 engines.
Rochester Quadrajets are plentiful, serviceable, and very tunable. Small primary bores kee
2. Quadrajet Carburetor
Tuning the Quadrajet is not as tricky as you might think. Dan explains: "I start with the primary jets and metering rods and look at the difference between them. For example, if the jet is a 70 and the metering rod is a 40, the difference is 30. That's a general baseline. From there, it's a matter of experimenting, moving two numbers at a time until you find which combination provides the highest manifold vacuum measured at the intake manifold or the lowest e.t."
Dan's tip: Smog engines not only had lower compression, but also leaned-out fuel metering in the carb for emissions purposes. Both took a bite out of performance, some of which can be adjusted with a simple rejetting. When tuning your carburetor, start at a 30 numbers difference between the jet and the metering rod for high-compression engines, and 32 numbers difference for low compression.
The Crane XR-I fits completely under the distributor cap; frees you from ever having to ch
3. Ignition Components
Dan suggests starting with a few basics like fresh plugs and plug wires. He uses ACDelco plugs and reproduction wire sets from Lectric Limited or M&H Electric. "We've never had an issue with them on any of our stock builds or dyno runs," he says. Increasing plug gap by no more than 0.005-inch [over recommended settings] may be worth a try, also, as it forces the coil to produce a bigger, higher-voltage spark.
A reliable module eliminates the frequent maintenance and sometimes-iffy performance of points and ensures top performance. "I'm a big fan of the Crane XR-i module with rev control built into it," Dan notes. "It takes the place of points and has an adjustable rev limiter built in. They're only around $70. Other manufacturers' modules have rev limiters, but the Crane is easiest to set, in my opinion."
Dan also uses and recommends Crane's matching PS20 coil. It's a black canister type, so it looks stock.
Dan's tip: Get your ignition system's basics up to speed with new plugs and wires, and use a Crane XR-i module for top performance and driveability. Use its rev limiter to prevent over-revving.
Engine vacuum is a sure measure of engine efficiency, and not subject to normal manufactur
4. Ignition Timing
For ignition timing, Dan keeps it simple. "A lot of guys don't like this, but I'm a racer and I only worry about the total mechanical advance. The big 455 H.O.s and Super Dutys with stock compression can take anywhere from 36 to 42 degrees of total mechanical advance, and I try to get it in by 2,500 rpm. That's a lot quicker than the factory setup that brings in all the advance by 4,000-4,500 rpm. With that said, every engine is different and some experimentation is required to find the sweet spot.
"For a high-compression engine with a mild cam, I'd probably want a little more mechanical advance because they can't tolerate as much initial timing as a low-compression engine can. Most 400s [except Ram Air IVs] have 10 degrees of initial timing, but I like around 12 degrees initial timing as a rule of thumb. Pontiac engines seem to like that."
With initial timing set to 12 degrees, and mechanical advance bringing the total to between 36 to 42 degrees by 2,500 rpm, some additional tweaking will get you to your engine's optimum setting.
Dan's Tip: Starting with 12 degrees initial advance, use mechanical advance to bring the total between 36 and 42 degrees total, all in by 2,500 rpm. Try a few degrees plus or minus to see what your engine likes best.