On The Level : oil deep stick

We all know oil is the life blood of the motor, but did you know there was power hiding in the amount of oil you use?

Words And Photos: Richard Holdener

We all know oil is the life blood of any motor. A motor without oil pressure is basically a ticking time bomb. It’s not a matter of IF, but a matter of WHEN it will blow up.

Given the importance of oil pressure, it is not uncommon for enthusiasts to err on the side of excess when it comes time to fill the crankcase. Often, even the oil pan manufacturers seem to recommend excess capacity for their oil pans. The problem with the more-is-better philosophy on filling the oil pan is that (ironically) the situation actually reduces both oil pressure and power.

That’s right folks, too much oil can be every bit as problematic as too little. Though we would always err on the side of too much (less power and lower oil pressure is always better than no oil pressure), the ideal situation is to have the correct amount.

Oil pans are typically rated in capacity, but the ratings are just approximations. The ideal capacity is the amount that provides the optimum combination of oil pressure and power.

The 496 stroker test motor featured a COMP solid roller cam and a Brodix induction system topped off with a Quick Fuel 950 carburetor.

To illustrate the effect of oil level, we ran a few tests on a 10.0:1, 496 big-block Chevy. The stroker was equipped with a SCAT stroker crank and rods, JE forged pistons, and Total Seal rings. The induction system consisted of a set of Brodix heads and single-plane intake topped of with a Quick Fuel 950 carburetor. Ensuring the combination made plenty of power was a COMP solid-roller cam (and lifters) combined with a double-roller timing chain and hardened pushrods. Also present was an MSD distributor, Meziere electric water pump, and 8.5-quart oil pan and pick up designed for a jet boat.

The combination of components worked well together, but initial pulls (after break-in) produced lackluster power. After timing and jetting, the power was still less than expected, and worse yet, the oil pressure curve was far from ideal. A dramatic fall off in pressure limited safe engine speed. The last thing you want to do is try to rev through an oiling issue. Better to find and cure the problem than continue with the dyno session.

Working with the Brodix aluminum heads and single-plane intake was a complete MSD ignition system that included a Pro Billet distributor and Blaster coil.

Exhaust for the oil test exited through these 2.125-inch long-tube dyno headers.

The oil test was run out of necessity in an effort to cure both low power and a falling oil pressure curve. Be aware that both too much and too little oil in the pan can create a drop in oil pressure.

Adjusting the oil level on this 496 not only produced a steady oil pressure curve, but increased the power output significantly (see power graph).

Lucky for us, Westech’s Steve Brule has decades of experience with big-block Chevys and knows the oiling system limitations all too well. Because too much and too little oil in the pan will often show the same symptoms, we started out by adding ½ quart of oil; the situation only got worse. We then drained 1 full quart (basically the ½ we just put in plus ½ from the original total), and were rewarded with an increase in both power and oil pressure. Removing ½ quart of oil raised the oil pressure and allowed us to safely run the motor to 5,200 rpm before the pressure dropped.

We knew we were headed in the right direction. Removing another ½ quart increased engine speed by 500 rpm (to 5,700 rpm) before the pressure dropped, then the next ½ quart out cured the pressure drop completely. Additional oil removal resulted in a drop in pressure at high rpm, from lack of available oil. Dropping the oil level on this big-block from 8.5 quarts to 7 quarts increased the power output by more than 35 hp (from 632 to 669 hp) but, more importantly, provided a consistent oil-pressure curve. When it comes to oil, too much or too little, and it’s too bad!

Effect of Oil Level on Oil Pressure-496 BBC

The oil pressure graphs illustrate the dramatic change in oil pressure made by adjusting the oil level in the pan. Dropping from 8.5 quarts (green) down to 8 quarts (purple) increased overall pressure significantly and allowed the big-block to rev cleanly to 5,200 rpm before experiencing a drop in pressure. The next drop to 7.5 quarts (blue) allowed the motor to rev to 5,700 rpm before the oil pressure started dropping. Removing the final 1/2 quart, to 7 qts total (red), resulted in a consistent oil pressure curve. Check out the power curves to see how the change in level (and pressure) negatively affected the output.

Effect of Oil Level on Horsepower-496 BBC

The initial runs on the 496 produced both lower oil pressure and low power. The excess oil produced windage, which limited both oil pressure and power production. Each successive reduction in capacity from 8.5 quarts to 7 quarts resulted in more pressure and power. Dropping down below 7 quarts resulted in a drop in oil pressure at the top of the rev range, from oil starvation. At this point, the oil capacity could not keep pace with the balance between flow and drain back. With the capacity right on the level, the 496 produced 669 hp and 605 lb-ft of torque. The change in oil capacity resulted in a gain of more than 35 hp!


Sources
powerperformancenews.com