In a Chevy big-block, it’s essential to maintain not just oil pressure but also oil control. Controlling where the oil goes in the engine can be an issue even for a nearly stock engine turning moderate RPM. When the RPM climbs, this situation really demands attention.
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What is done in the lube department on an all-out race engine can amount to 50 and possibly as much as 90 hp. The potential gain for a street engine taking care of business, even with mostly stock parts, is as much as 25 hp.
The first thing you need to deal with is oil pump selection. With a stock or even a pretty healthy modified unit, there is nothing to panic about as far as retaining reliability while utilizing a stock or nearly stock oil pump. However, that does not mean that there is no work to be done.
The stock oil pump gets the job done on any engine that is good for 600 to 650 hp and 6,800 to 7,000 rpm. All you need to concern yourself with is that you bought a good stock pump and not a cheap offshore-produced item made to questionable tolerances. If the stock pump gets the job done, why consider alternative and most likely more expensive pumps? Although there are numerous answers to this question, the most obvious is that the more money you have in the engine build, the more sense it makes to better protect that investment. A number of oil pumps are available that provide both improved reliability and additional power.
Although it may come as a surprise to some, a Chevy big-block’s oil pump can draw well over 10 hp at 7,000 crankshaft rpm. Use a grade or so thicker in viscosity and that can go up another 5 hp. On the other hand, pay attention to the system’s efficiency and you can divert as much as 10 hp from what the oil pump absorbs and put that to good use at the rear wheels of your vehicle.
Wet- versus Dry-Sump Systems
If it is a question of which is best, a wet sump or a dry sump, dry is the way to go. Dry-sump systems provide better lubrication for max- performance applications. One of my favorite builds, done for a Lola T165 Can-Am car, was a dry-sump engine. But at the end of the day, I have to admit it was far from a budget unit and is out of the scope of this book.
Because I am covering budget engine builds, I am not going to discuss dry-sump systems in great detail. If you want to build a dry-sump engine, give the guys at Moroso or Reher-Morrison a call; either company has all the parts needed and all the instructions necessary for you to build one onto your big-block.
Standard- versus High-Volume Wet-Sump Pumps
Most performance enthusiasts choose a high-volume pump over a standard-volume pump. Why? Because bigger must be better. However, let us not overlook the fact that most pumps start bypassing oil at a little more than 2,000 rpm. And this means that the pump is delivering too much oil at 2,500 rpm. So why would you even think about a high-volume pump? In many applications, a standard oil pump provides enough volume.
Just for the record, a stock set of pump gears shortened to 1 inch in height gets the job done if bearing clearances are correct.
For most street applications a stock-style pump from a reputable source is good up to about 550 hp and 6,000 rpm, but do not rely on a cheap knock-off pump. If you are rebuilding an engine, the original pump could well be acceptable. If no trash goes through the pump they tend to last semi-indefinitely. As for oil pressure, the stock spring is set for about 45 to 50 psi and, within that range, it should, with a good oil, be more than enough to get the job done.
If more than 550 hp and 6,000 rpm is targeted it’s time to think about upgrades. To upgrade the pump for 6,500 to 6,800 rpm, for example, the Melling 77060 spring (color-coded black) goes to 60 psi before bypassing, and the 77070 (color-coded pink) 70-psi is good for engines turning up to 7,500 rpm. Summit Racing is an easy source for these springs.
Many companies offer wet-sump pumps. Oil pumps require both short-term testing on the dyno and long-term testing on the track. Therefore, I have not tested every pump out there to the degree that I prefer. As a result, I have had to rely not just on my own testing but also on that of pro engine builder associates of mine whose work is tested every weekend at the track.
The pumps with which I have had experience, other than stock, are Melling, Moroso, CVR, Titan, and Schumann. I have already examined the stock-style Melling pumps. Now I want to discuss the “up-market” pumps that you might consider using on a higher-end build in the $12,000-and-up range.
I have extensive experience with Moroso’s billet pump. I have used several of them in applications from all-out race to high-output big-inch street builds. It’s an all-around effective pump just as you would expect from Moroso.
The CVR pump is currently (2014) being tested. I have had some good reports on it and am confident it can get the job done.
Titan also makes an exceptional pump. I first used a Titan pump in a Chevy big-block in 1998. In 2010, when I tore the engine down, the bearings in the 1,500-plus-hp race engine were still in top condition, and that’s strong proof of the quality of the pump. If I have to build a serious engine, this pump is one of my first choices.
The Titan pump uses a gerotor- style pumping element instead of the more common intermeshing gears. This is an inherently more efficient means of moving oil from point A to point B. However, whether the potential benefits of higher pumping efficiency and lower parasitic losses are realized is highly dependent on how well it is installed on the engine.
A gerotor pump has a disadvantage: it doesn’t handle contaminant ingestion as well as a gear pump. For a dry-sump system, controlling contamination is only a matter of prepump filtration. For a wet sump, it is another deal altogether. That said, many production engines use a gerotor-style pump without any undue problems from contamination. At the end of the day, the choice is yours.
Last on my list of pumps are those from Schumann. This company’s high-performance pumps don’t look that much different from other stock-style pumps, but looks can be a little deceiving. Most notable is that the pumps contain a ball-actuated pressure-relief valve instead of the more usual cylinder style, which is almost universally used by pump manufacturers. In theory, the ball valve should have a greater dynamic pressure-control range than a cylindrical valve, and this should result in better pressure control. However, the oil that is bypassed is not routed back to the intake cavity of the pump as with most other pumps. Instead, the excess oil can be routed back to the oil pan floor. Although my experience with this pump is limited, it does seem to hold the oil pressure very steady.
Oil control can be a significant problem for Chevy’s big-block. With the lifter valley wide open down the center, oil from the heads returns to the pan by dropping straight onto the spinning crankshaft. This operation produces two negative consequences: First, the oil dropping onto the crank increases windage losses. Second, the crank acts like a giant eggbeater and aerates the oil, which results in aerated oil being fed to the bearings. Also, if equipped with a hydraulic cam, the oil fed to the lifters, being aerated, can compress, thus losing lifter opening area and control.
The spinning crank in a Chevy big-block acts as a poor propeller driving the oil to the front of the engine. This is why flat-tappet cams fail at the rear lifters, and the rear bores are worn to a greater extent than those up front. Once the oil starts to become entrained in the crank, it becomes a runaway process and levels out only when about 2 quarts (and sometimes more) are actually rotating with the crank. This causes a dramatic output loss. Mark Dalquist of Throttle’s Performance and I were testing a 565 drag race engine when we saw crank oil entrainment cut output by 80 ft-lbs. This is about the most extreme case I have seen with a big-block but losses of half that are easy to encounter.
The first rule here is to never overfill the pan. Many stock pans have a horizontal surge baffle so the oil level can run surprisingly low before any loss of oil pressure occurs. In fact, if you are racing a really low-buck engine with a stock pan, you need to investigate running up to a quart low. In most cases, running a quart low produces a real cheap 7- to 10-hp gain at the top end. Low oil levels (to be used with due caution and a keen eye on the oil pressure gauge until the oil level has proven to be adequate) are the first step toward reducing oil entrainment.
The next zero-cost situation is to have as much oil as possible return to the crankcase from the heads via a route different from the stock. First is the following simple fix: Moroso has a kit to glue a wire mesh into the lifter valley over the oval holes. Once completed, even the small amount of blow-by from well-sealed cylinders causes air to come up through the mesh more easily than oil can pass down through it. The result is that it acts as a partially effective one-way valve and it substantially reduces the amount of oil dropping onto the crankshaft. However, for this mod to be the most effective, you need to give the oil from the heads an alternate route back to the crankcase. Figures 3.18, 3.19, 3.20, and 3.21 show what needs to be done in that department.
The standpipe arrangement that Mark Dalquist made up for a project engine gets the job done better than the wire-mesh arrangement. But this requires much more time to make. These mods are performed to control oil flow and (the often overlooked) motion of air within the crank-case. This is a big deal in Formula 1 engines and this line of thinking is proving to be beneficial to a measurable degree even in engines that may never see more than 7,500 rpm.
If the build is an all-out max- performance engine, the usual practice here is to plumb in oil return lines from the front and back of the block to a point just above the oil level in the pan. These lines need to be large (possibly larger than you may have expected). The reason is: If crankcase vacuum is drawn on the valve covers, the airflow is from the pan up and this impedes the oil’s return to the pan. Here you need to think in terms of 3/4-inch-bore return pipes.
All this work to the return system looks excessive and may prompt you to question how much it may be worth in terms of output. But the answer is: far more than you ever thought might be the case. Although it is somewhat of a variable, taking care of even the simple stuff can be better than 20 hp at the top end. If you are talking in terms of an 8,500-rpm drag race engine, that number can be as high as 80 hp!
Pulling a vacuum on the crank-case, either via a mechanical pump or by means of an exhaust evacuation system, allows the development of more power (as discussed in Chapter 12, Exhaust Systems). It is possible to pull as much as 9 inches Hg (4.5 psi) with an exhaust-driven system, and as much as 24 inches Hg (11.8 psi) with an engine-driven pump.
Dropping the crankcase pressure does two things: First, it causes the droplets of oil to drop out of suspension in the now rarified crankcase air much more easily, and this can significantly cut windage.
Second, it generates a positive pressure across the rings at all times during wide-open-throttle (WOT) use. This brings about nearly continuous seating at all critical moments during the engine’s four cycles. It also brings about better sealing against the cylinder walls, and this in turn means lower ring preload on the bores (often called lower tension, but it’s actually lower compression).
My personal experience here is limited to the Moroso crankcase vacuum pump, but Reher-Morrison and others also offer a race-proven big- block kit. As to what crankcase vacuum is worth, check out Figure 3.23.
I mentioned pans earlier, but I want to emphasize their importance. An oil pan’s job is not only to prevent oil surge from starving the bearings of oil, but also to keep the oil away from the rapidly rotating crank.
Written by David Vizard and Posted with Permission of CarTechBooks