We’ve spent the last 12 months collecting technical tidbits that we think could be useful for budding engine builders and general engine junkies who can never get enough of internal combustion tech. This is material we’ve gathered from engine builders, manufacturers, tuners, and our own experience in building (and breaking) engines. If you like what you read here, let us know and we’ll ramp this effort up and start a more aggressive course of collecting more that may not make a dent in the technological progress of mankind, but it might just make your day a tiny bit brighter, and your session in the shop a little easier and more productive.
1. Estimating Flywheel HP
We’ll begin with a favorite that we learned from both Steve Brule’ at Westech Performance Group and Ben Strader at EFI University. This is a very simple yet surprisingly accurate way to estimate horsepower for either race or street engines.
The first step is to estimate the maximum amount of torque per cubic inch. Brule’ likes to use 1.25 lb-ft per cubic inch for a 10:1 compression street engine with good cylinder heads and a decent camshaft. Race engines with more compression and more highly tuned will obviously make much more than that. We’ve heard that pro level drag race engines making upwards of 1.7 lb-ft per cubic inch. Jon Kaase told us that his Engine Masters engines make around 1.5 lb-ft per cubic inch. For this example, we’ll use the street engine number of 1.25.
Let’s use a 434ci stroker small-block Chevy as an example.
Step 1: Estimate the engine’s peak torque:
Brule’s formula assumes a 10-percent loss in torque between peak torque and peak horsepower.
Step 2: Multiply peak torque x 0.90:
This number is the amount of torque the engine will make at the peak horsepower RPM point. Ben Strader uses the same formula but prefers 0.88 as a multiplier for race engines operating at higher engine speeds.
This leads us now to where we estimate the engine’s peak horsepower RPM point. This is the engine speed where the engine makes peak horsepower. For our small-block example we’ll estimate that it makes peak horsepower at 6,700 rpm.
Step 3: Multiply torque at peak horsepower, times peak horsepower’s RPM:
This happens to be the upper half (the numerator) portion of the classic horsepower equation which is: HP = (TQ x RPM) / 5,252
Step 4: Resolve the rest of the horsepower equation:
Peak horsepower is estimated to be 622.8 HP at 6,700 rpm.
If the estimated horsepower number is discovered to be low, but the peak horsepower RPM point was accurate, then the original torque-per-cubic-inch number was probably low. So if that 434 actually made 650 hp then we could substitute 1.3 lb-ft per cubic inch. When we run that new 1.3 number through the equation, the result equals 647.8 hp, which is very close.
Performing a second example using Strader’s version of the equation, we applied this to the JeselEqual Eight engine that you recently read about in EngineLabs. Using a torque-per-cubic-inch number of 1.52 and using Jesel’s 12,000-rpm peak horsepower speed, and using Strader’s 0.88 multiplier, the equation spits out an estimate of 1,305 hp while Jesel says the engine should make 1,325 – which puts the equation within 2-percent. According to a well-known race engine builder, he feels that Jesel’s number is low and will likely make even more than 1,325 horsepower. We’ll see soon enough.
Using this equation, you can amaze your friends by quickly doing the math on your smartphone and estimate power fairly accurately. If nothing else, it’s an accurate glimpse into how engines work.
Dyno testing takes all the guesswork out of engine power, but you can use this formula to accurately evaluate where peak power will ultimately fall.
2. Grease it Right
Any performance product works best only when used properly. Something as simple as dielectric grease is constantly being misused and causing problems. Many enthusiasts are under the mistaken impression that this grease is a conductor – it is not. Dielectric grease is an insulator - which means it should not be used directly on any electrical connector –including spark plug wire connectors.
Where it should be – and is recommended to be used – is to lightly coat the inside of the spark plug wire boot. This prevents heat from welding the boot to the spark plug ceramic. The best way to accomplish this is to use a small screwdriver or a cue tip to lightly coat the inside of the spark plug wire boot while avoiding the spark plug wire connector and/or the connector on the spark plug itself.
Since the dielectric grease is an insulator, laying a glob of this grease inside the plug wire connector will increase the resistance at the connection and reduce the voltage applied to the spark plug. Since we want as much potential voltage to be directed to the spark plug as possible, it should be obvious that using the dielectric grease should be done as carefully as possible.
MSD’s version of dielectric grease is called Spark Guard. Just keep it away from all electrical connections; this stuff is an insulator not a conductor.
3. Accelerator Pump Fix
Hot rods and fast cars tend to spend a majority of their life in the garage. This fact of life can cause problems for carbureted engines, especially after the car has sat for several months. On Holley-equipped cars we’ve noticed that occasionally the accelerator pump circuit appears to have failed. Many blame this on the pump diaphragm and sometimes that does occur. If you find the diaphragm has become brittle, we prefer to use the green, Viton rubber diaphragm from Holley (PN 135-10). These are impervious to most of the nasty additives in current gasoline (xylene, benzene, toluene, and others) and will remain pliable over many years of service.
If the original diaphragm is still serviceable, the next place to look is at the anti-drain-back valve located directly underneath the accelerator pump nozzle. This valve is a small needle that allows fuel to travel past the seat when the throttle is moved yet prevents fuel from draining back into the float bowl when not in use. When the engine sits for a long period of time, the fuel evaporates and can cause the needle to stick to the seat.
Removing the accelerator pump nozzle and gently prying the small needle assembly should break it loose. Don’t hit the accelerator pump circuit with the nozzle removed and this needle in place, or it will shoot out of the passage and could launch into the engine or out someplace where you will never find it – so be careful. With the needle freed up, replace the accelerator pump nozzle and check for proper accelerator pump action.
If you discover your carburetor is missing this check valve needle, the fuel will drain back slightly and cause a mild hesitation. If you need to purchase this needle, Holley sells it under part number 121-5 and is available through Summit Racing.
Remove the accelerator nozzle on a Holley carb and look for the needle-shaped check valve and make sure it is free to operate properly.
4. Save the Seals
Here’s a tip from Induction Solutions owner Steve Johnson. We asked him how often we should change the seals on our nitrous solenoid especially when using a pulsed nitrous controller. He said that the big killer for nitrous solenoid seals was constant exposure to bottle pressure. The more time the seals are exposed to bottle pressure, the shorter amount of time they will live.
He suggested using an in-line nitrous ball valve combined with a nitrous purge solenoid. His recommendation was to locate the ball valve in the interior within easy reach of the driver and that the valve should be closed and the pressure eliminated in the line between the valve and the nitrous solenoid with the purge solenoid.
The quarter-turn valve is available with options of -4, -6, or -8 AN male fitting adapters and could also be a great safety shutoff item should the nitrous line to the solenoid be accidentally severed. Johnson recommends closing the valve just after the run and purging the line to cut the pressure.
We placed our nitrous quarter-turn ball-valve in between the front seats and added an Induction Solutions pressure gauge. Bleeding line pressure is accomplished with a purge solenoid just before the nitrous solenoid.
5. Necked Down
The science of squeezing more power from the small- and big-block Chevy is nowhere near its end game. We recently had a discussion with Bob Florine, the general manager at ARP, regarding a somewhat esoteric question about head gasket loading using the mix of shorter length vs. longer head studs for both the small- and big-block Chevy engines. It appeared to us that with a shorter head stud that the same torque application on the stud would produce a different reading compared to the longer head studs.
Florine told us that a long time ago, Can-Am racer Jim Hall proposed to ARP that they build the shorter length head studs with a reduced shank diameter in the middle of the stud. This would create more stretch with the shorter studs. By doing so, after the head gasket relaxed slightly, the shorter, undercut stud would maintain the proper head gasket clamp load and prevent a potential leak.
With power-adder horsepower numbers escalating almost daily, the idea now has increasing merit. In the ARP catalog, these studs are called undercut (U/C) studs. There are literally dozens of part numbers for this design across multiple engine families including four- and six-cylinder inline Chevy engines, small-block Fords, and multiple import engines that use short/long head stud length configurations, which benefit from the undercut design..
Note the reduced shank diameter on the shorter studs on this small-block Chevy engine. The reduced diameter allows more stretch to maintain the proper clamp load even if the gasket partially relaxes.
6. LS Lifter Launch
Our friends at Comp Cams tell us that once the valve lift on hydraulic roller lifter LS engines exceeds 0.660-inch, it’s a good idea to step up to a tie-bar-style roller lifter. Comp’s Billy Godbold tells us that their experience on the Spintron has shown that with a rocker ratio of 1.7:1, at 0.660-inch of valve lift, lobe lift is at 0.388-inch. In order to achieve this amount of lobe lift, the base circle becomes smaller, which drops the lifter down enough that there is a chance the lifter body will slip out of the plastic holder.
The LS engines use the plastic valve lifter guides to align the roller lifter wheel with the cam lobe. If the lifter “falls out” of the guide flats, the lifter can turn and then be jammed back up into the plastic holder. This quickly destroys the guide and allows the lifter to spin in the lifter bore, which places the side of the lifter wheel against the lobe on its next pass. You don’t have to have much of an imagination to visualize the damage that ensues when this happens.
To be safe, Comp has limited maximum valve lift on its latest series of Low Shock Technology (LST) LS cams to 0.632-inch of valve lift (0.372-inch lobe lift). Godbold told us “Sometimes you can be just fine with 0.390-inch of tappet lift, but if you build enough LS engines, you will get bit from a spun lifter if you go much past that 0.372-inch limit.”
If you choose to run a cam with more lobe lift, the tie-bar-style lifter is the way to go. Comp offers drop-in hydraulic rollers lifters with the tie-bars, or if the effort requires it, Comp also has mechanical XD, Endure-X, or Sportsman tie-bar-style roller lifters. All of these options eliminate the factory plastic lifter guides. While tie-bar lifters are more expensive, they minimize the chance of destroying an engine because you pushed the LS valve lift envelope a little too far.
Combining more than 0.372-ich lobe lift with the stock plastic roller lifter guides can allow the lifter to drop out of the bottom of the guide. If this occurs, bad things will result.
7. Budget SBC Accessory Drive
Few performance enthusiasts pay attention to the 4.3L V6 Chevy. It was Chevy’s attempt at a budget 90-degree V6 created by dropping two cylinders from a small-block Chevy. While it wasn’t a performance engine, it does offer one important advantage. If you’re thinking of converting the V-belt accessory drive on your small-block Chevy to a serpentine system, that V6 can help. Hunt up one of these V6’s that were commonplace in the 1988 and up S-10 trucks, Blazers, and GMC Jimmys.
This accessory drive will bolt directly up to almost any small-block. If the donor vehicle is in decent shape, you could unbolt the alternator and power steering pump all connected to the cast aluminum driver side accessory bracket. Make sure to also retrieve the crank pulley and the passenger side A/C bracket. If you don’t need the A/C pump, that’s fine – leave it behind but take the bracket, idler, and tensioner pulleys. Be sure to keep all the bracket bolts as well.
Dorman offers an A/C delete pulley that bolts right in place of the A/C pump with the same size pulley so the OE belt length remains the same. The beauty of this system is that if you blast and powder coat the brackets, this system will look awesome for a very modest investment. Plus, if you ever need replacement parts like an idler or tensioner pulley – these will be factory replacement parts for typical 1990 S-10 4.3L V6. The only custom part might be the Dorman A/C delete pulley (PN 34152). This makes for a very affordable, durable, and compact accessory drive.
A 4.3L serpentine belt accessory system will bolt right up to any small-block Chevy as long as there are accessory bolt holes in the heads. In this application, we’ve replaced the A/C compressor with a Dorman idler pulley.
8. Locking Header Bolts
Some things about performance engines can be downright aggravating. If you work on enough engines, you’ve likely been victimized by a header bolt that just won’t stay tight. In our experience, it is rarely all the bolts but instead just one or two per side that loosen up over time. If that wayward bolt remains loose for a long enough time, the exhaust temperature and pressure will blow out the gasket and create a massive exhaust leak that is truly annoying.
Here’s a fix that just might solve that problem. ProForm offers these locking header bolts that incorporate tiny saw tooth style washers underneath the bolt head. As the bolt is tightened, these teeth lock together and prevent the bolt from loosening. In most things in life, it’s the simple solutions that tend to work the best. The ProForm part number for the typical 3/8 x1-inch NC header bolt is 66756 and you can find them at Summit Racing.
Note the small saw tooth locking teeth on the interlocking washers. These teeth prevent the bolt from losing its grip on the header flange.
9. All About Microns
Microns are not a new adversary in the upcoming Star Trek movie. A micron is a measurement – defined simply one-millionth of a meter and equal to 0.000039-inch. The reason this is important is because all fuel and oil filters are rated in microns. But there seems to be much confusion around micron numbers with regard to fuel filters for EFI systems.
The easiest way to remember all this is that a bigger number micron filter allows larger dirt particles to pass through. So a 100 micron filter will allow dirt that is 10 times larger to pass through compared against a 10 micron filter.
The accepted standard with fuel filters is to place the less restrictive 100 micron filter upstream of the pump to remove the large dirt particles that could damage the pump. After the filter, it’s best to use a 10 micron filter to remove damaging material that could plug up an injector. If you need a final analogy to help, think of it this way: a 100 micron filter will allow big rocks to pass through while a 10 micron version will filter out the sand. Get it? Got it? Good!
Fuel filters can all look the same, so the only way to tell its filtering capability is to look for the laser-etched markings on the end of the filter. This is a 10 micron filter. In the background is a stainless mesh 40 micron filter used with E85 fuel. Don’t use paper filters with E85 as the alcohol creates a chemical reaction that creates a nasty gel.
10. Create Your Own Ignition Advance Curve
This tip is aimed at the more traditional engine crowd that uses a conventional mechanical advance distributor. Many think that creating a custom advance curve may be beyond their skill level, but the truth is it’s pretty easy. Many also think that a custom curve requires removing the distributor from the engine and putting it on a distributor machine. We’ll show you how you can determine your advance curve without removing the distributor. All you need is a timing light, a timing tape, a tachometer, and a pad and pencil.
The best and most accurate way to perform this little test is with a digital dial-back timing light. We’ve used an Innova digital dial-back light that incorporates RPM into the display, making this task really easy. If you don’t have a dial-back light, you can use the degree marks on your balancer. If your balancer is not degree’d, you can use MSD’s timing tape to display the advance degrees directly on your balancer.
With all those puzzle pieces in place, disconnect the vacuum advance from the distributor and then write down five or six data points every 250 rpm from 1,000 to 3,000 rpm on a piece of paper. Now rev the engine to each of those RPM points and read the timing. With all the data points recorded, you now have a curve that you can plot on a piece of graph paper or just do a simple graph in Excel on your computer.
Now that you have the curve, you can make changes to lighter or heavier springs to adjust the curve. Then re-test and you can see the results by comparing the curves. This is a very simple way to establishing the curve and if you keep a record of the modification, you will know how each one affects the curve in case further tuning is necessary.
This simple curve — created in a basic spreadsheet program — illustrates how timing advances against RPM in a typical mechanical advance distributor.