A Slippery Subject
Mike O’Brien; Brooks, KY: I have a question on oiling systems regarding the difference between a high pressure oil pump and a high volume oil pump. Assuming the oil pump is working fine and pumping to capacity, does your engine actually see any increase in oil flow from a high pressure oil pump or high volume oil pump if its internal passageways are not capable of passing any more oil? It would seem that a high volume oil pump would push the relief valve off its seat and bypass the oil. On the other hand, it would seem that a high pressure oil pump would flow more oil because the relief valve would stay shut longer and the increased pressure would push more oil through the constricted passageways. Even if the engine is turning a high rpm, only the oil passing the internal passageways would arrive. I think the only time an engine might benefit from a high flow oil pump would be if the OEM pump were providing insufficient oil to begin with. What say ye?
Jeff Smith: The great thing about car crafters is their insatiable appetite for information. While this might seem like an obscure question, it’s actually relevant to all street engines. The easiest way to think about moving fluid is understanding that pressure and volume are inversely proportional. That means if you wish to move a greater volume of oil, pressure will be reduced. If pressure increases, volume will be reduced. The classic example of this is a garden hose filling your Saturday morning car-wash bucket. With an open garden hose, you get high volume at low pressure. Place your thumb over the end of the hose, and the pressure inside the hose increases. The water squirts over a greater distance, but the volume is reduced since it will now fill your bucket more slowly.
An engine lubrication system operates much the same way. Because the oil pump can supply far greater volume than the restricted oil galleries can support, pressure begins to build in the system. At idle, for example, a small pump spinning relatively slowly still creates sufficient pressure. Since the pump is spinning slowly, most of the time the pump is supplying only enough oil to maintain a given pressure. As rpm increases, pump output also increases to the point at which the pressure pushes the pump’s internal oil pressure relief spring to open the relief valve slightly. The amount of oil that is bypassed is directly proportional to what we could call the internal oil leaks in the engine. Main and rod bearing clearances are major contributors to this leakage, along with the volume of oil that reaches the top of the engine to lube the valvesprings and the guides. The greater the number of internal oil leaks, the more volume it requires to fill that demand. If the volume demand is great enough, oil pressure will drop if the oil pump cannot supply sufficient volume to maintain the pressure. This rarely happens because the design engineers have done their homework. What is more common is when a high volume oil pump is used in an engine with tight clearances. At higher engine speeds, the pump has far more capacity than the engine needs, and a greater volume of oil generally ends up at the top of the engine, flooding the valvetrain. In certain circumstances, this can result in the high volume oil pump actually sucking the pan dry. We’ve heard of instances of this occurring with high-rpm LS engines with stock oil pans. One reason this occurs with LS engines is because the factory gerotor oil pump spins at crankshaft speed instead of half speed, as is the case with most older engines where the pump is driven off the camshaft.
The simplest way to create a higher pressure oil pump is to merely increase the spring pressure required to open the relief valve. This can be accomplished by either adding higher-rate spring or shimming the existing spring. To move a greater volume of oil requires taller pump gears. For example, Melling’s stock-volume, small-block Chevy oil pump uses a pair of spur gears that are 1.20 inches tall. A high- volume Melling pump increases the height of these gears to 1.50 inches. These 25-percent-taller gears can move a greater volume of oil. Of course, there is also the potential to build a high- volume / high pressure oil pump that combines the attributes of both styles.
So you might see that an engine with standard or slightly tight clearances (which reduce the internal oil leaks) really doesn’t need a high-volume pump. Therefore, a typical performance street engine doesn’t need a high- volume pump if the clearances have been properly set. When employing a high-volume and/or high pressure oil pump, the only thing that is really achieved is greater parasitic power losses required to spin that bigger pump. And if a higher pressure is employed, the only real result might be higher oil temperatures. The classic Smokey Yunick recommendation of 10 psi per 1,000 engine rpm is certainly OK, but we’d be willing to offer that your typical street engine could survive just fine on 50 psi of max oil pressure, 7 when spinning to 6,000 or 6,500 rpm. Idle oil pressure is even less critical, since there is no load on the engine. Many car crafters freak out when idle oil pressure drops below 30 psi at idle, but anything above 10 to 15 psi is probably acceptable. This is because there is very little load on the engine. Automatic transmissions place a slightly higher load on the engine—but that can be 40 lb-ft or less, which is still pretty low.
To put this in perspective, I called Jon Kaase Racing Engines (JKRE) and asked them what those 800-plus-cubic-inch Pro Stock engines run for idle oil pressure. JKRE’s Cliff Moore told me idle oil pressure is often well below 10 psi, and on some of their engines the pressure is actually zero. Moore says, “We just put a piece of tape over the warning light.” The reason they are not concerned with this idle pressure is that they know the pump is circulating oil (much like the water hose filling the wash bucket), but there is no pressure indicated because the clearances are wide enough that they do not present a restriction. This is an extreme example, but it does illustrate the point. As an additional example, the engine in this month’s 406ci small-block buildup generated more than 70 psi of oil pressure at 6,000 rpm, and we think if we had spent the time to reduce the oil pressure to around 55 psi, we might have been able to increase power slightly.
Oil viscosity plays a big part in this discussion. The basic premise is that tighter bearing clearances increase bearing load capacity but also reduce oil flow past the bearing. As a result, the temperature of the oil at the bearing increases. The opposite is also true: Wider clearances reduce load capacity but increase oil flow volume with subsequent lower oil temperature. Building an engine with tighter bearing clearances allows the engine builder to use thinner-viscosity oil (assuming the load capacity is sufficient with high-pressure additives and high-shear stability). Lighter-viscosity oil will flow more easily through tighter clearances and reduce the temperature rise. Conversely, wider bearing clearances demand a thicker-viscosity oil. We hear rumors of NASCAR teams experimenting with SAE 0–viscosity engine oil combined with tighter tolerances all in search of reduced engine friction and parasitic loss required to drive the oil pump.
In the Nov. ’09 issue, Westech’s Steve Brulé and I did an oil-pump test on a small-block Chevy (you can find this story archived on CarCraft.com). We tested four Milodon pumps on a Dart 372ci small-block Chevy ranging from a standard-volume unit, a high-volume unit, a high-volume high-pressure pump, and even a big-block Chevy pump. The average horsepower numbers tell the story
As you can see, the stock-volume and pressure pump produced an average of almost 5 more horsepower over the high-volume pump. The odd thing was the only slight power loss from the high-volume/high-pressure pump. But these results clearly support the concept that a stock pump works pretty well. The exceptions to these low- pressure rules are engines like the 351C and 429/460 Fords that feed the main bearings through the lifters. These engines require more oil pressure than priority main-fed engines because the lifters act as a restriction, so more pressure is required.
Melling Automotive Products; Jackson, MI; 517/787-8172; Melling.com
Milodon; Simi Valley, CA; 800/828-8224; Milodon.com
After being sidelined by the scuttled Super T10 in his Chevelle, Tech Editor Smith was offered an ’11 Cadillac CTS-V wagon to drive on Sunday at the Spectre 341 Challenge. Jeff’s best time in the Caddy was 3.51, and the experience left him longing for an LS-A engine in at least one of his Chevelles.
Spectre hired HeliTahoe to get aerial footage of the 341 Challenge on Sunday. You can see the videos on Spectre341Challenge.com. BTW, want to get married in a helicopter? HeliTahoe offers HeliWeddings—get married in a chopper over Lake Tahoe. Check that out at HeliTahoe.com
These are typical self-aligning rockers identified by the two guide tracks that straddle t
Gary Hoerner; Saratoga Springs, NY: I have a question regarding self-aligning rockers on Chevy TBI motors. I have a ’91 350 TBI motor that is using full roller rockers instead of the self-aligning stamped rockers. Will this hurt anything? The heads are 191 and the pushrod reliefs are slotted, not round, so there is not much side-to-side movement.
Jeff Smith: If we go way back to the early days of the small-block Chevy, the designers came up with what was back then a radical departure from shaft rockers with an inexpensive stamped rocker arm that pivoted on a simple stud and a half-sphere ball. Lateral movement of the rocker arm was limited by the slot cut in the cylinder head for the pushrod. As performance engine builders cranked more lift and duration into the camshaft and added roller rockers, it made controlling lateral movement more difficult. That’s when pushrod guideplates became the standard, also requiring hardened pushrods. Then in the late ’80s, GM came up with a guided rocker arm that featured two small rails stamped into the rocker arm valve tip used to retain the rocker over the valve tip. This required a slightly taller valve-stem tip to protrude slightly beyond the valvespring retainer to locate the rocker. Along with guided rockers, the small pushrod slots in the head were opened up, and in some cases the entire pushrod area between the intake ports was windowed completely to save weight.
The only real warning with a system like this is to avoid combining guide systems. This means you should not use pushrod guideplates with guided rocker arms, as this could create a bind situation. In your case, Gary, using the pushrod slots in the heads to locate the rocker arms will work, but it may allow the rocker to migrate sideways across the top of the valve tip. The ideal situation would be to modify the heads for screw-in studs and guideplates that would ensure the rocker arm is properly located over the valve.
LS Truck Engine Power
Mike Ptacek; Brookville, KS: Some time ago you did a story on an LQ4 short-block that made 480 hp. I was impressed with the numbers the carburetor with the Hot cam pulled. I have an LQ4 that had an engine fire when my wife was involved in an accident with our crew cab. She is almost completely healed. The truck was an ’02 with only 50K on it, and the factory intake and wiring was damaged. I am planning to build the motor for a kit car I have. The only problem in using your setup in the article is I believe it is going to be too tall for my application. Cutting a hole through the back window is not an option on this car. I like the price of the carburetor setup, but I think I will have to go with an LS6 intake. Does anybody have any numbers for the same setup except with an LS6 intake? Do you recommend GM’s stand-alone engine controller, although it is expensive?
A low-profile LS1 or LS6 intake manifold is much shorter than either the truck manifold or
Jeff Smith: First of all, it’s good to know your wife is OK. Cars and parts can be replaced. Since the carbureted manifold appears to be too tall for your application, the simplest and easiest conversion would probably be to retain electronic fuel injection by using the low-profile intake manifold used on the early Corvette/Camaro LS1/LS6 engines. Before we get into the specifics of the swap, keep in mind that using this manifold will also require changing the front accessory drive to accommodate the lower position of the throttle-body. The truck accessory drive will crash into any induction piping that leads to the throttle-body, so you have two choices. First, you could use an early, factory F-body–style accessory drive. This will require replacing all the brackets and using a different power steering pump and an F-car harmonic balancer. This could get expensive, and this system is hard to find used because they are in such demand. I’d suggest using Kwik Performance’s conversion kit that allows you to retain the truck balancer and use Kwik’s brackets to reuse the truck alternator as well. You will have to purchase a new power steering pump, but they are not expensive, especially if you get them through Rock Auto. The Kwik Performance bracket kit that mounts just the power steering and alternator is PN K10168, which sells for $287.00. If you want to relocate the factory A/C compressor, Kwik makes a separate mount for that as well.
When using the LS1/LS6 intake, which should be easy to find used, the real question becomes how to control the fuel injection. Since this is an ’02 engine, it uses the older-style 24x crankshaft shutter wheel with a cam sensor at the back of the engine. You could use a factory computer and aftermarket wiring harness. It appears you might get lucky here because both the LS1 and truck injectors are rated at around 25 lb/hr. The computer can generally compensate for this flow difference, but it will still require an aftermarket wiring harness. For example, Painless sells a wire harness for late-model LQ4 engines using an electronic throttle and 4L80E trans that sells through Summit Racing for just a touch more than $1,000. While that seems a little pricey, the beauty of this system is that you have a factory computer with control over the system, including the use of a mass airflow sensor (MAF). Plus, purchasing this harness from Painless qualifies you for a powertrain control module reflash service from Painless based on what you need. This makes the price a bit more palatable and worthy of consideration. Along these lines, there are also other aftermarket companies that offer factory-compatible wiring harnesses that may come in a little less expensive.
FAST makes an EZ-EFI system to control your engine, and you get to choose the air/fuel rat
Our pals at Tuned Port Induction Specialties (TPIS) have been working on LS engines since they first came out. TPIS’ Jim Hall reports that on a recent LQ4 dyno test, he fitted an engine with a TPIS ZL11 cam (215/220 degrees of duration at 0.050-inch tappet lift, and 0.560 inch of lift on both the intake and exhaust) and an LS1 intake manifold and the engine made 441 lb-ft of torque at 4,700 rpm and a solid 443 hp at 5,900. He said with an LQ9’s higher compression, you could expect those numbers to jump another 15 lb-ft and 10 hp. This is at the limit of what the stock injectors can deliver for fuel flow.
Another approach is one that few car crafters are aware of. If you have an engine like an LQ4 or LS2 that does not have a computer or wiring harness, FAST has created a very affordable EZ-EFI system designed for EFI engines. You are probably familiar with the self-learning EZ-EFI system, but in summary, it uses a wide-band oxygen sensor that reads the existing air/fuel (A/F) ratio and then the computer matches that to the target A/F you load into the computer. As you drive, the computer reprograms itself and establishes the injector pulse widths needed to establish those target ratios. For example, at part-throttle cruise, you tell the EZ-EFI you want a 14.7:1 air/fuel ratio, but at wide-open throttle the engine should run at 12.9:1. After a few runs, the computer has established these parameters, and all you have to do is drive around. The best part about this technology is that the FAST system configured for your engine (PN 30200) is priced at $873.95 from Summit Racing. One advantage to EZ-EFI is that while proper injector sizing will still be necessary to make the desired horsepower, the computer really doesn’t care what size the injector is, as it tunes for your specific combination. Be aware that EZ-EFI is a fuel-only system, so you will need an ignition controller. The best one on the market is the MSD 6LS (PN 6010) that will plug right into your LQ4 engine. This adds another $319.95 (through Summit Racing) to the cost of your system, but it is virtually a plug-and-play type of system.
But since injector sizing is an important criterion, let’s quickly go over what it will take to make 450 hp with your combination. Right away, it will be difficult to make that much power with stock injectors. There are several online calculators that will do this work for you, but it’s also important to know the variables involved with injector sizing. For example, these Gen III engines run at higher fuel pressures, as much as 58 psi line pressure, or four bar (one bar is sea level pressure of 14.7 psi). Fuel injector flow rates are often expressed in three bar standards, or 43.5 psi. Just a change in fuel pressure from three bar (43.5) to four bar (58.8 psi) will increase the flow rate of the injector by more than 12 percent. The simplest way to calculate the injector size you need is to use a brake-specific fuel consumption number of 0.50 with a standard 43.5-psi line pressure and an injector duty cycle of no more than 85 percent. Duty cycle refers to the amount of time the injectors are open relative to the amount of time they are closed. At 85 percent duty cycle, the injector is open for 85 percent of the time and closed the other 15 percent. You must size your injectors to deliver enough fuel at or below 85 percent duty cycle at wide-open throttle. This is important because holding the injectors open 100 percent of the time will burn them up. We won’t go through the math formula, but trust us that 450 hp will require a minimum of a 33 lb/hr injector at 43.5-psi line pressure. If you jack the line pressure up to 55 psi, a smaller injector will deliver this horsepower, or this same 33-lb/hr injector will be capable of nearly 500 hp.
Fuel Air Spark Technology (FAST); Memphis, TN; 901/260-3278; FuelAirSpark.com
Kwik Performance; Springfield, MO; 417/955-1467; KwikPerf.com
Painless Wiring; Fort Worth, TX; 817/560-8324; PainlessPerformance.com
Tuned Port Induction Specialties (TPIS); Chaska, MN; 952/448-6021;
Random ’69 Camaro. I don’t think we met our quota for the month yet.
Spotted at the Summer Nationals: massive turbocharger in a third-gen Firebird.
Spin to Win
Jim Klug; Milwaukee, WI: I have a ’71 Vega ex-bracket car that I am converting to a Pro Street–type car. My current combo is a 350 Chevy with 10:1 pistons and bowl-blended fuelie heads with 64cc chambers, a Turbo 350 trans, a Ford 9-inch rearend with 4.11:1 gears, and 33-inch-tall M/T Sportsman street tires. The converter stalls between 2,300 and 2,700 rpm. I am trying to use an Edelbrock street tunnel-ram with two 465-cfm Holleys. The cam is an Isky 280 Mega cam. The specs are 0.485-inch lift, with 232 degrees of duration at 0.050-inch tappet lift on a 108 lobe-separation angle advanced 2 degrees. How do I get this package to work? Do I have enough gear ratio? I am just interested in nuking the tires. This car will not be raced, only street driven. Right now the car drives great. The converter seems a bit tight, but OK. This car just will not smoke the tires. I have a couple of other camshafts including a 270 Isky Mega cam and a Comp Mutha Thumpr. I’m just really interested in having the car really sound wild. Also I have a 400 10:1 motor with Vortec heads and an Edelbrock Air-Gap intake. What would be the best bang for my buck?
The problem is it just doesn’t have the grunt to turn over these big old 33-inch tires. I even tried taking off the tunnel-ram and putting on a dual-plane LT1 intake with a 600 Holley. I also have 4.56:1, 4.88:1 and a set of 5.13:1 gears and a 3,100 to 3,500 converter to try. What gears, converter, cam, or 400 engine would make this work. I don’t want to use a grenade on it!
Vacuum-secondary carbs on a tunnel-ram can be made to work well. We discovered that smalle
Jeff Smith: Let’s see if we can help you out, Jim. Let’s start with effective gear ratio, because you are correct in thinking you don’t have enough gear. As the rear tires become taller, they reduce the effective gear ratio. So in your case, if we use a 26-inch-tall tire and a 4.11:1 gear ratio as our baseline, adding the taller tires reduces the effective gear ratio to a much more conservative 3.23:1. Turning the math around to get close to an effective 4.11:1 gear ratio with those 33-inch-tall Mickeys will require every bit of that set of 5.13:1 gears. To equal the effective gear ratio of a 4.11 gear with a 26-inch-tall tire, you would need a 5.20:1 rear cog. So one reason you can’t “nuke the tires” is you just don’t have enough leverage. Plus, keep in mind that in addition to their height, those massive Mickeys are also pretty wide, so you need the additional leverage that the gear ratio supplies to help strike the tires. But there’s much more to this equation.
Working our way up the drivetrain, torque converters play a big part in strong acceleration. There’s far more to converters than just the stall speed. Effectively, the stall speed merely raises the rpm where the converter hits. By raising the stall speed, you bring the launch rpm closer to the engine’s torque peak. For maximum acceleration, you want the stall speed at least above the peak torque rpm, which for a 350ci small-block like yours is probably around 4,500 to 4,800 rpm. So looking strictly at the stall speed, the loosest converter you have would also help since it would push the engine farther up into its torque range to help overpower those tires. But wait, there’s more. What creates torque multiplication is an internal component known as the stator. The stator consists of a series of blades located between the engine-driven impeller and the turbine, which is splined to the transmission input shaft. The stator redirects fluid from the impeller to change its direction, but at the same time it also multiplies torque. Maximum torque multiplication is achieved with the greatest difference in speed between the impeller and turbine, which occurs right near zero vehicle speed. This multiplication factor is in the range between 1.8:1 and 2.5:1 depending upon the style of stator used. With a 2.0:1 multiplication factor, an engine making 300 lb-ft of torque could produce as much as 600 lb-ft of torque for that instant of initial acceleration. Unfortunately, this only occurs at maximum stall torque ratio. As the vehicle moves forward and the speed difference between the turbine and the impeller is reduced, the multiplication ratio diminishes rapidly. This is important because additional torque will make the car launch much harder and, in your case, make it much easier to spin the tires. The best way to get this information is to call your torque converter manufacturer. A combination of more torque multiplication and a higher stall speed will put much more torque to the rear tires.
Of course, we can’t forget the engine. In terms of just making torque, the single, four-barrel, dual-plane intake package should make more torque than the tunnel-ram, but much of this also has to do with tuning. A poorly tuned carburetor on that dual-plane will not perform as well as a pair of small Holleys on a tunnel-ram. Several years ago, we did a story testing a Summit tunnel-ram package using a pair of 600-cfm Holley 0-1850s on a tall tunnel-ram (“Tunnel-Rams for the Street,” Dec. ’08). We learned that the pair of vacuum- secondary 600-cfm Holleys generated far more accelerator pump shot than the engine really needed, and it bogged badly right off the line because the engine went dead rich. By reducing the accelerator squirter size in both carbs down to 0.022 inch, we radically improved the engine’s throttle response. I used a pair of 0.050-inch squirters and filled the outlet holes with epoxy and then drilled them to 0.022 inch. Of course, a stock Holley 0.021-inch squirter (PN 121-121) would also work, but we didn’t want to wait, so we made our own. This might be a big part of your problem. If the carbs have been modified, return the primary jetting to stock and see how that works.
You didn’t mention it, but your initial timing is also critical for making low-speed torque. For an engine like this with a big cam, I’d set the initial timing at 18 degrees and (with the vacuum advance disconnected) check the total timing. The engine will want somewhere around 36 degrees or possibly more total timing because of those old cylinder heads. If the engine doesn’t rattle (detonate), then the timing should be pretty close for optimal power. All of this should be enough to seriously improve both the throttle response and the engine’s low-speed torque. Then you can spin the tires until the cords scream for mercy.
Holley Performance Products; Bowling Green, KY; 270/781-9741; Holley.com
This was one of the historic engines on display in the GM Performance Division booth at the Summer Nationals. In the ’70 Buick GS, these made 360 hp at 4,600 rpm and 510 lb-ft at 2,800 rpm, the highest torque rating at the lowest rpm of any GM production engine.
The holding area for the Miss Car Craft Summer Nationals contestants. I’m feeling a movie plot developing here . . . we make dreams come true!
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