The service life of any engine depends greatly on the quality and properties of the oil used. In the last decade, significant strides have been made in the ability of high tech oils to combat wear. At the turn of the millennia you could expect a streettuned (about 1 hp per cube), daily driven small-block Chevy fed on a diet of topnotch synthetic oil to run for 250,000 miles and still deliver quality performance. These days, if you have chosen the right parts and use the right oil, a half million miles is most certainly possible.
There’s no secret to achieving this longevity. Many factors influence the situation, but the most important are oil changes at regular intervals. 3,000 miles on even synthetic used to be considered the oil change limit for those of us who loved our custom hot-rodded street engines and could not afford to be re-building them every 50,000 miles (or less). I have a Magnuson-supercharged extended-cab Chevy truck and with what I have invested, it had better run 300,000 miles at least. And it will—and so will your Chevy if you follow the advice given here.
Let’s deal with the 3,000-mile oil change interval first. Use a good synthetic and a good oil filter and you can very safely double that and more than likely triple it. Even though the good oil costs more, its extended life means you will be paying less overall—and that is an economy right there. The only really effective way to find out if the oil needs to be changed is to have an oil analysis done.
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However, that costs about $20 to $25. You could have spent that money on new oil, so is an oil analysis worth even the minimal effort involved? Yes, but not just to establish whether or not an oil change is needed. I have an oil analysis done on my vehicles about every 30,000 miles and this tells me whether or not everything inside the engine is still as it should be. If not, the analysis gives me an early warning.
The next question will probably be: “Where can I get an oil analysis done?” Tracking down a lab that does this can be a pain, but a source that is easy to find and is cheap is through an Amsoil dealer. To find the nearest to you go to Amsoil.com.
Since the first edition of this book, there has been a big panic among the cam companies over the loss of Zinc Dithio Phosphate (ZDP) in API certified oils. This additive was removed from the oil because of possible contamination of catalytic converters. The ZDP is a highpressure lube that is close to essential for the survival of a flat tappet cam and lifters—especially at break-in.
Without ZDP you would have to run a cam with very mild acceleration rates for it to survive. A cam intended to be used with ZDP will last only a few hours without it. The good news is that although those oils at your local parts store may not have ZDP, you don’t have to buy oil that meets API requirements. Most of the companies that brew raceorientated street oils are not concerned about getting API certification. They are more concerned about power and having your engine last because their reputation hangs on it. If your engine is going to utilize a flat-tappet cam, and there are certain occasions when it is your best torque/power option regardless of cost, be sure to utilize an oil with ZDP in it. You will find plenty of recommendations in these pages.
If the right oil is used, the bearing and bores of a small-block Chevy are of little problem in terms of longevity. At the end of the day it really is the cam and lifter contact patch that is the critical lubrication point. As far as oils that will work in respect to an engine equipped with a flat-tappet cam, there are a few I have tried on the dyno, at the track, or on the road. Let’s start with a look at what you might use on the track. Here, I did a mega-buck test on the then new (as of 2004) Joe Gibbs Racing (JGR) oil that’s used in the team’s Cup Car, which at the time was driven by Tony Stewart. Apart from my own tests on the dyno with several different engines and 1,000+ circle track miles, I got to use Gibbs’ $1.5 million dyno for a day of testing with one of Tony Stewart’s restrictor plate Talladega motors. A comparison was made with some of the best race oils out there and it came out on top, even if it was only by a margin of 1.3 hp. And just in case somebody mentions that you cannot dyno test to that sort of accuracy, then all I have to say is: “You have obviously never used a 1.5-million-dollar dyno!”
But the Gibbs oil might just be a little pricey for many and, though very good at developing a race oil, Gibbs is not the only kid on the block. I have also used Amsoil, BND, Redline, Mobil race oil, Valvoline race oil, and UPM oil. The non-API flat-tappet oils supplied by these companies each have a healthy dose of ZDP, making them ideal for a flat-tappet engine. Also these companies, and especially the Amsoil and BND, have blends that are long life deals on the street and can be used confidently to 9,000 miles.
Power Versus Oil Type
An often-posed lubricant question is whether one oil will produce more horsepower than another or, indeed, whether or not pouring an additive into the engine will help horsepower.
In most cases concerning additives, it’s “buyer beware.” Since there are so many variables and products to consider (many of which I have yet to test), I can’t be specific in this area, but I can pass on my experiences.
Synthetic-oil manufacturers claim their products produce more horsepower because they are slicker. This may or may not be the case, but evidence from my dyno testing has shown that thinner oil does produce more horsepower. For instance, running a mineral oil at 200 degrees F and then increasing the oil temperature to 220 degrees F will produce at least 3- to 4-hp more in a typical 300-hp motor.
Running mineral oil at 230 degrees F is pushing it near its temperature limits.Certainly, going as high as 250 degrees F is a marginal situation, like treading on thin ice. Synthetic oils, however, are fine to 300+ degrees F. Additionally, their viscosity doesn’t change as much as mineral-based oils with rising temperature. This means the oil can be thinner to start with and deliver the benefits in terms of extra power without the need to run such high temperatures.
Within the limits of the dyno’s accuracy, my tests have showed no measurable difference between mineral and most (but not all) synthetic oils when both were run at similar temperature developed viscosities. Many of the test results indicated that, with mineral oils, coolant temperature needed to be 170 degrees F and lubricant temperature around 220 degrees F. It’s difficult in practice to get the oil temperature this much hotter than the coolant temperature. When synthetic oils were used, the engine delivered the same kind of horsepower with lower oil temperatures.
A potential power increase does exist when synthetic is used. In an engine of around 400 to 450 hp at 6,000 to 6,500 rpm, a synthetic running 20 degrees cooler looks to be about 2- to 4-hp more. Such numbers represent the limit of test accuracy on a typical dyno and only can be verified by meticulous tests and averaging a number of test runs.
Using this technique, most synthetics appear to be worth on the order of 0.5-to 1-percent-more power. At the time of this writing, the oils that I use are BND for both street and race, Amsoil for the street, and JGR oil for race applications.
If you are a street or street/strip hot rodder on a very tight budget, these oils may seem like they are a little over the top for your budget engine, but consider this: If you had to struggle to find the cash to build it, isn’t it better, as far as possible, to make sure you give your hard-earned investment the best protection possible? Granted, the higher initial expense can be a problem when cash is really short. Fortunately, most synthetics can be diluted as much as 50/50 with a good grade regular mineral oil and still retain better than 75 percent of the synthetics’ advantage. For break-in lubrication, a good oil is needed, but a long-life synthetic is overkill because it will only be used for a few hours. For break-in, I use Castrol GTX, Valvoline, and Pennzoil, plus whatever cam break-in additive the cam company calls for. If I’m buying the oil for my vehicles, I use only the best. Internal inspections at 50,000 to 100,000 mile intervals and oil analysis at 20,000 or so miles show it pays off. And for what it’s worth: none of my vehicles get an easy life. Even my tow truck gets raced!
Although lubrication is its primary function, oil is also an important cooling medium. Pistons rely on a significant amount of oil splash cooling on the underside. Although, for wind age loss reasons, oil needs to be kept away from the rotating assembly, a certain amount has to be present for cooling purposes.
This leaves us with a trade-off situation. If the oil is too hot, it may be better initially for reduced windage losses, but this can lead to overheating. Even if no oil film breakdown occurs at the bearing, pistons can weaken due to the elevated temperatures and detonation is more likely. Conversely, excessive cooling can lead to viscous drag losses.
Generally, the higher the RPM, the more piston heat there is; therefore, more oil probably is needed to cool the piston.
Unfortunately, higher RPM means a greater necessity to keep oil away from the crank because the losses go up with the square of the engine’s RPM. Doubling the RPM means four times the windage loss. In other words, if we can cut windage loss by 2 ft-lbs at 4,000 rpm, this will represent about 8 ft-lbs at 8,000 rpm. That may only be 1.5 hp at 4,000 rpm, but this escalates to a whopping 12.2 hp at 8,000 rpm. So what’s the best trade-off?
In a naturally aspirated engine, there’s usually enough oil splash to adequately cool pistons, especially if synthetic oil is used and temperatures kept to the 190- to 200-degree mark. If temperatures escalate much over that, there may be a penalty of needing thicker piston crowns, slightly lower compression, and so on. If the subject is a nitrousinjected motor, then an entirely different situation exists. Short of paying a machine shop to put in piston oilers, the best plan, if the pistons have not had a thermal barrier coating as described in Chapter 4, is to keep the oil temperature down to the 170 mark. This may call for a bigger pan or an oil cooler. If the nitrous system is only up to about 150 hp and jetted suitably rich, any good oil will get the job done.
There is hardly any point of using the best in oils if your choice of filter is not equally informed. If you are on the dyno for break-in, be sure to use a good filter for the actual break-in, then use a really good one from there on.
If you are breaking-in on the street and intend to use the break-in oil for 250 to 500 miles before changing it, use a topnotch filter from the get go. As of 2009, I usually use a Purolator Pure One, a Fram filter, or my stainless mesh System One filter for the first half hour on the dyno. When the initial break-in has been completed, the oil is dumped and the synthetic is poured in. The filter is then changed for whatever checks out the best at the time (things can change quickly in this area), and at the time of this writing it looks like Amsoil has the hot ticket in terms of flow and filtration capability. If you cannot locate an Amsoil dealer, an equally good choice should be the aero quality K&N oil filter.
The original 265-ci small-block Chevrolet was introduced without an oil filter. The following year the canistertype oil filter set-up was added and was used until 1968. Subsequent small-blocks used a different adapter in the filter housing and a spin-on filter. That was used until the late 1990s, when production of the small-block as we know it ceased.
For most purposes, the earlier filter was a good deal. In general, the element flow used in early filters was higher, with typically 90 to 95 percent of the oil passing through the bearings also going through the filter.
The later, spin-on cartridge filters eased filter changes. However, the shorter ones have a lower capacity and can’t handle the full output of the pump, especially when the oil is thick during a cold-start situation. To accommodate this, an oil bypass valve is located in the filter spin-on housing bolted to the block.
The bypass valve usually lifts off its seat at a maximum of 14 to 15 psi, but when the oil is cold it’s not uncommon for the pressure differential across the filter to exceed the bypass-release pressure. This results in unfiltered oil going direct to the bearings. Since the oil pick-up is at the bottom of the pan, where most of the debris settles out after shutdown, we find the filter is bypassing oil at a time when its filtering action is needed most.
At this point you may be tempted to block the existing bypass valve or install a filter adapter with no bypass valve. Before you’re tempted to do this, consider the possible problems.
First, plugging the filter adapter valve and using a stock-size (and flow) filter can mean a bigger pressure drop across the filter. This can reduce the pressure fed to the bearings. Also, the pump relief valve is likely to come into operation sooner, so the quantity of oil available at the bearings will likely be further reduced.
In addition, if the oil pump has a high-pressure relief valve, the pressure generated while cold could burst the filter, so now your oil is being pumped onto the street rather than through the bearings. If the filter doesn’t burst, consider that the extra resistance to flow through the filter means more stress on the pump and more power to drive it.
What’s probably a better alternative, especially if you’re working within a budget, is to use the larger small-block Chevy truck filter. With this you can expect to achieve the filtration performance typical of the early canister filter.
If you want to stick with a more or less conventional paper-type filter (as apposed to a steel mesh filter), then Amsoil and K&N Engineering have, as of 2009, among the best on the market. The filtering element of either of these filters flows about 250-percent more than a typical OE filter, while taking out particles up to about 40-percent smaller. The Fram HP filter is also a good, cost-effective choice with about twice the flow of most normal filter units.
If the budget allows, another type of filter I recommend is the System One. This filter uses a stainless-steel mesh and can be stripped for cleaning and reused. The System One is a direct replacement for the stock filter and is available in short and long cartridges. The strong point of this type is the ease with which a debris inspection can be made. An average OE-style filter is good to about 25 to 30 microns, but bypasses so much potentially dirty oil that this can become almost academic. A System One filters to about 45 microns, but because it flows about 800-percent more than an OE type unit, it filters all of the oil.
The reason System One can be a good first-filter choice is that they allow near instant oil analysis after break in, by inspecting what has been stopped by the screen. Since these filters come apart, it’s easy to see the debris collected on the filter element. On the other hand, opening up a paper filter is a pain.
Attempting to inspect the fuzzy surface of a paper filter is difficult because it camouflages much of the debris. The stainless element doesn’t do this. Since test engines are run for a relatively short time in terms of mileage, and are always on a diet of clean, fresh oil, the microparticle filtration capability of a stainless screen becomes academic, since it would do in most cases on a race car. For street vehicles where oil changes may be as much as 9,000 miles apart rather than at about every 30 to 35 miles, I use Amsoil or K&N paper-element filters.
The factory stock small-block Chevy pump is effective and reliable, but not perfect. It’s common practice to install a high-pressure, high-volume pump. In many cases this is simply not necessary and drains power that could be used to lower your ETs.
The stock oil pump is good to at least 400 hp, and RPM of 6,500 to 7,000. Unless your motor will exceed this, it can be used stock unless you want to improve overall performance and cut power consumption. For engines within these limits, the stock pump’s 45-psi oil pressure is all that’s required.
Increasing the oil pressure just to be on the safe side may not prove as safe as you think, since it’s possible to have too much oil pressure. Unnecessarily raising the oil pressure causes higher oil temperature and greater parasitic losses driving the pump. Look at it this way: the higher the oil pressure, the more backpressure there is to resist the turn on the pump. This means it takes more power to turn the pump. Not only is excess pressure an obstacle to power production, but also excess volume.
If the stock pump has adequate volume, installing a high-volume pump, which bypasses all the additional volume, serves only to reduce power output. Consider whether your application needs anything other than the stock pump. If it doesn’t, don’t spend your money on a higher-pressure higher-volume pump.
Although adequate for most applications, the stock pump can be improved. If you rework the oiling system, or just the main cap where the oil pump locates, the ease with which the oil discharges into the block will have been improved. This results in less pressure loss between pump and bearings.
Internal Pump Clearances
It’s relatively minor here but if you want to get picky and have several pumps (used or otherwise) to choose from, a unit with tighter clearances can be built. The normal clearance between the gear OD and the case is between 0.002 and 0.004 inch. By selecting the housing and gears, a pump with 0.002-inch clearance instead of 0.004 can result. The gear-tocase end clearance is between 0.002 and 0.004 inch. If excessive, it can be reduced by lapping the end of the case on a flat surface. By reducing leakage, the pumping action is improved.
Oil pumps must be sized to satisfy low, not high, RPM requirements. A misconception is that engines need more oil as the RPM increases. However, the oil pressure/volume requirement isn’t necessarily in proportion to the RPM. Bearing clearance does not significantly increase with RPM, but the pump’s output does. Unchecked, an oil pump’s output increases far beyond requirements unless limited by the pressure relief valve. Consequently, all oil pumps have excess delivery at peak engine RPM. Because they are sized for the low-RPM applications, the oil-bypass system assumes a relatively important role. If bearing clearances are at the wide limit in an effort to cut bearing losses, tightening up the pump clearances helps idle oil pressure to the tune of 2 to 3 psi. At a 650- rpm idle, 10 psi is fine, but the pressure better be up to about 35 psi by the time the motor is turning 1,800 (or so) rpm.
Oil Pump Chatter
A characteristic of a small-block Chevy pump is a pulsating oil flow, which can cause pump chatter. This same vibrating motion also hits the distributor since its drive originates from the same point. This can cause a little spark scatter and inevitably lead to a small reduction in power output.
One way to reduce pump chatter involves the use of a die grinder. Remove the pump’s top cap and inspect the discharge port in the cavity. On some pumps, during rotation, the driving gear intermittently covers part of the port. This causes the port’s discharge area to change as much as 18 percent as the gear teeth go by. If the gears on your pump intermittently cover the discharge port, grind a lead-in with a bias directed toward the idler gear. Regardless of whether the gear covers the discharge port, it pays to streamline the entry because flow at the point where the gears mesh is disoriented.
Porting the discharge port not only increases the pump’s volume of flow but also cuts the power needed to drive it. A popular way to further reduce pump chatter on a stock seven-tooth small-block Chevy gear pump is to cut anti-chatter grooves into various parts of the body. How these grooves operate to overcome chatter has never been satisfactorily explained to me, so for want of a theory, I’ll simply give you mine.
The anti-chatter grooves operate on two principles. First, they apply pressure to the end of the gears, which in turn presses them onto the end of the case for friction damping. Second, the grooves spill some of the oil as it’s squeezed from the meshing gear teeth, thus making the trapping pulse less severe. If this is the case, then any anti-chatter grooves may have the effect of reducing the pump’s output. This, of course, won’t be of consequence if the pump’s output already exceeds requirements.
Most stock small-block Chevy pumps deliver oil pressure between 35 and 45 psi. Most are right around the 40-psi mark. On occasion, changing to synthetic oil on an engine with the pressure relief valve at the lower mark will cause the oil pressure to drop as much as another 5 psi. If a sagging relief valve spring is suspected, buy a new spring and compare the stiffness and length to the existing one.
If an increase in oil pressure is required, fit a stronger spring—Chevrolet P/N 3848911 for 55 to 60 psi—or shim up the existing spring. If you shim the spring, be careful that you don’t limit the travel of the piston such that it will not bypass the oil adequately.
On stock small-block Chevys and most replacement pumps, the oil is bypassed internally. This means that if the oil pressure at the outlet side goes above the bypass valve setting, the bypass opens and returns the oil to the pump’s intake side. At high RPM, a high bypass condition exists, which means some oil may circulate a number of times before being delivered to the bearings. This causes the oil to be unnecessarily heated.
Though the amount of heat put into the oil doesn’t constitute a major problem, steps can be taken to reduce it while increasing pump efficiency. Within reason, the larger the return to the inlet side of the pump, the better. On most pumps this can be improved by taking out the press-in plug on the cross-drilling that connects the pressure relief valve drilling with the intake, and re-sizing it. You also can help improve the return flow by accessing this area with a die grinder and radiusing off the edge of the cross-drilled hole.
A rarely used alternative to dumping the bypassed oil back to the inlet side of the pump is to bypass it directly back into the pan. Although nothing complex is involved, stock pumps rarely are modified to do this. There’s no difficulty modifying an existing pump if you have access to a few simple pieces of equipment. Essentially, it involves blocking off the original transfer hole between the pressure relief valve and the pick-up pipe drilling. When plugging the hole, make sure a totally air- and oil-tight fit is produced. If an air leak exists, it will compromise pump performance.
With the original bypass blocked, you need to consider how the bypassed oil enters the pan. Unless precautions are taken to the contrary, the opening pressure relief valve can send a high-pressure stream of oil straight into the pan. This can splash-aerate the oil in the pan considerably (we will see, in Chapter 7, how this can cost measurable horsepower), so it should be put through some kind of grid to remove some of its kinetic energy so that it drops into the pan and creates less splashing.
Another method is to couple up a pipe to the pressure relief valve passage and direct the oil toward the side of the pan. Adopting this technique achieves two things: it cuts the temperature of the oil, and it appears to markedly reduce pump chatter. This indicates that the pulsing bypassed oil is fed through the transfer passage back into the intake side is aggravating the system’s tendency to pulse.
By externally bypassing oil, a problem can be created on the induction side of the pump as the demand through the pick-up pipe is increased greatly. This can cause the pump to cavitate and momentarily starve the bearings. To combat this, the stock 1/2-inch pickup, which at best is marginal, needs to be enlarged to about 5/8-inch diameter.
Alternative Oil Pumps
Though there are ways and means of up-rating a stock pump, there are also good reasons for using a pump with different characteristics. For instance, if bearing clearances have been increased, and the engine is using a low viscosity oil or high operating temperatures are expected, then the situation may warrant the use of a high-pressure, high-volume pump. We’ve already discussed the technique for increasing the pressure of the stock pump, which may be a wise move if high RPM is to be used and bearing clearances are to remain relatively stock. Under these conditions, 55 to 60 psi of oil pressure is desirable, but certainly no more than this.
One of the major manufacturers of oil pumps is Melling, whose products are widely available. Melling makes a stock replacement pump plus a high volume pump (P/N 55HV), which delivers 27-percent more volume. This pump uses extended seven-tooth gears and is approximately 1/4-inch longer than stock.
Melling pumps are also equipped with stronger springs to increase the point at which the pressure-relief valve comes in. Springs available for the Melling pumps are color-coded according to stiffness. They come in plain, yellow, or pink, and their stiffness increases in that order. The plain spring sets the oil pressure at around 40 to 45 psi, the yellow one at about 55, and the pink one at 65 to 70 psi. Of course, these are hot oil pressures. When the oil is cold, pressures will be considerably higher.
If you’re installing a replacement high-volume pump, be aware that these pumps are longer. If you use the stock pickup, it runs into the bottom of the stock pan, so an appropriate Melling pickup must be used.
Another alternative is to use a big block pump for a regular small-block Chevy. The big-block pump has about 30-percent greater flow rate than the small-block pump, and it has a 12- tooth gear arrangement instead of the normal 7-tooth gear of the stock pump. Suitably prepped with an external bypass, this pump can reduce spark scatter substantially.
Oil Pan Design
When the small-block Chevy was originally designed, the pan was simply an oil reservoir. As performance levels of both chassis and engines increased, weaknesses were found in the stock design. The stock pan falls short in two areas: First, a car that’s capable of accelerating or cornering rapidly causes most of the oil to move to one end of the pan and away from the pickup, resulting in loss of oil pressure. If bearings are to survive, it is vital to make sure the pump pick up is always immersed in oil under all conceivable operating conditions.
Second, the pan’s innards must exercise some control over the oil to limit crankshaft entrainment. It’s understandable to assume that since a crankshaft is rotating at a high speed, oil is centrifuged off. This is not the case. Granted, the rotating assembly centrifuges off a lot of oil, but much of the oil hits the crankcase or pan walls and bounces back into the rotating parts and becomes entrained. This can cost much more power than you may at first suspect.
Oil Pan Modifications
For a stock or near-stock motor, crank windage and oil entrainment in the crank may not appear to be of any great concern. However, some test results may convince you otherwise. Tests were made on a 400-ci equipped with a calibrated sight level in the drain plug hole. Oil was progressively added to the engine between power tests. At a little over a half-quart above the full mark, the crank began to gather oil.
Normal pan wind age and oil dispersion through the rest of the engine usually causes oil level at the sight plug to drop about three quarters of a quart. With a half-quart overfill, 4,000 rpm proved the critical speed where the crankshaft oil entrainment became significant. At this RPM, the oil level observed at the sight plug dropped almost two quarts and 10 hp disappeared. Most street motors regularly turn 4,000+ rpm, so this is significant.
In this test, the overfilled pan replicated the situation produced by a vehicle under acceleration. Unless adequately baffled, the oil will migrate to the rear of the pan. A 1-g acceleration rate will cause the oil to be at 45 degrees, which means the rear of the crank is well and truly immersed. Just because only one part of the crankshaft starts to dip into the oil doesn’t mean that entrainment stays local to that area. Under hard acceleration, the oil level rises at the rear of the pan, and the rear counterweight may start gathering oil. The most obvious conclusion is that oil will be entrained only at the rear of the crank.
In reality, because of the position of the counterweight, the crankshaft acts as a crude propeller and drives the oil forward. The oil then starts to form rope-like tentacles extending the length of the crankshaft. Even though the crank may only have dipped into the oil in one place, the wind age and viscous shear problem occurs down the entire crank length.
The shorter the stroke of the engine the less likely there will be any oil entrainment. But we are not dealing with anything less than a 3.48 stroke here. Oil entrainment is a reality in the pan of a 3.48-stroke engine and it gets worse very rapidly as the stroke gets longer. For a 383, oil entrainment is a factor that needs to be seriously addressed. With modern tires capable of delivering good traction, and the fact that any small-block Chevy can turn over 6,000 rpm, the oil pan needs attention, even for minimal performance applications.
For street vehicles, the most obvious solution is a horizontal pan baffle to keep the oil from the crankshaft. If ground clearance problems don’t exist, then use a deeper pan; the farther the oil reservoir is from the crankshaft, the better. If a deep pan cannot be accommodated, use a sheet metal baffle with appropriate drain-back holes to separate the oil from the spinning crank.
In an effort to reduce the amount of oil that remains on the walls, screens, and baffles, some companies coat the baffles and pan internals with PTFE. This encourages the oil to drain back into the reservoir area more quickly.
If a sheet metal wind age tray is used, a scraper blade on the left-hand side of the block (as viewed from the front) should be used to shear off excess oil. The excess oil then should be directed underneath the wind age tray into the reservoir below.
If the pan is shallow and there’s little room for scrapers other than one on the block, a slightly different approach is necessary. If a solid wind age tray is used, oil striking can bounce back into the rotating assembly. If a wire screen is used, it absorbs the oil’s energy on impact. This allows it to pass through the screen rather than bouncing back into the crankshaft. Shallow pans then can benefit from the use of a mesh screen, whereas a deep pan and those with effective scrapers and/or recovery areas often work best with sheet metal screens.
Making an effective sump is quite a science, and although fabricating your own is not beyond the skills of anyone handy with a welding torch and sheet metal cutters, guaranteeing top results is. I have had good results with pans from several companies but in the main I find that the Moroso range and quality of service well meets my needs.
If you go online to Moroso.com and check out the pans available, you will see the range is very extensive, even for just the small-block Chevy. Take your time selecting here because you will need to take into account the size and style of the rear main seals (crank to block and block to pan) as well as the application. If you have any problems selecting, call Moroso’s tech staff—this may save you returning an incorrect selection.
Top-End Oil Restriction
A significant proportion of the oil that finds its way into the crankshaft’s domain originates from the valvetrain. Motors with the stock-type ball-mounted rockers need a good supply to the cylinder head components of the valvetrain to prevent the ball and rocker assembly from galling and overheating.
If roller rockers are used, the need for a large quantity of top-end oil is eliminated, as roller rockers require only a minimal amount of oil. Some oil will be necessary to cool the valve springs, especially if they’re doubles incorporating a flat-wound damper. The damper spring performs its function by generating friction between the two springs, and friction generates heat. Without sufficient oil to remove excessive heat, the valve springs will quickly lose their temper and the closing force exerted will drop.
Oil for the lubrication of the upper end of the motor passes through the two lifter galleries, through the metering valve and the lifter, through the hollow stem of the pushrod, and out into the rocker. It drains back mostly via the drain-block holes at the ends of the cylinder heads, and from there it runs into the lifter valley. At this point the oil can pass back into the pan via several different routes. It can run out through the holes in the lifter valley, over the cam lobes, or down the drain-back holes at the front and back of the block.
If roller rockers are used, oil flow can be restricted at any number of points. Probably the best place to restrict the oil is at the lifter, but it’s not always the most convenient.The most popular method is to install restrictors at the back of each of the oil galleries. This modification only applies to solid-lifter-type applications, because hydraulic lifters need the additional oil for their operation. Restricting the oil at the back of the lifter galleries means there’s a lot less oil returning to the crankcase from the top end and getting entrained in the rotating assembly.
If a roller cam is used, it’s practical and desirable to plug the oil return holes at the center of the lifter valley. These holes usually serve to splash oil onto the camshaft for lobe lubrication, but with a roller follower this is unnecessary.
If a flat-tappet camshaft is used, it’s possible to plug or put stand-off tubes in these holes, but only if relatively short mileages are intended. If you intend to use a flat-tappet cam on the street, don’t plug them—it will lead to increased cam wear.
If the situation allows plugging of the holes at the center of the lifter valley (covered in Chapter 3), we have to assume that all the oil will return to the crankcase via either the two holes behind the timing chain or the drain-back holes at the back of the block. Generally, it’s best to encourage the oil to drain back to the pan via the back of the block rather than from the front.
For a drag-race engine, keeping the oil drain-back in the back rather than in the front is no problem, since acceleration forces it to the back of the block anyway.
For a road-race engine, the acceleration forces cause the oil to go down the back and, under braking conditions, down the front. Engine horsepower isn’t needed during braking, so it’s not super-critical.
In any event, it pays to make sure the block drains the oil down the face of the block, underneath the timing chain, and on to the pan as rapidly as possible. That’s because getting back on the throttle may cause the oil that went through the front holes to be collected by the crank.
If roller rockers are being used, it pays to put a debris screen in each of the return holes in the block. Sometimes, a rocker will break up, and when it does, needle bearings will pass into the lifter valley. If these get to the oil pump, the results are disastrous. Using epoxy resin, a screen can be installed in each of the four oil-return holes.
Written by David Vizard and Posted with Permission of CarTechBooks