| We've all heard about the three inevitabilities in life: | | | | between the rings and cylinder wall means less |
| death, taxes, and a mother-in-law who thinks you | | | | friction. |
| don't deserve her daughter. For racers, there's at | | | | Finally, given the same deck height, shortening the |
| least one more: the nagging suspicion that you are | | | | stroke means you can stuff in a larger rod. A |
| down on power. Whether it's true or not, it's | | | | higher rod/stroke ratio reduces the maximum |
| always fun to dream about how many more | | | | angle between the center of the rod journal and |
| races you could win with just a few more ponies | | | | the center of the wrist pin when the piston is |
| spinning the crankshaft. With that in mind, Circle | | | | centered between TDC and BDC. This reduces |
| Track humbly presents these 15 tips for getting | | | | the tendency of the rod to try to push the piston |
| more power from any engine. Try not to burn up | | | | into the cylinder wall, also reducing friction. There |
| the tires. | | | | is a limit, however. Generally, increasing the rod |
| Maximize Compression | | | | stroke ratio pushes the powerband higher in the |
| It's a simple rule: Compression equals power. Of | | | | rpm range. If you push the ratio too high, the |
| course, everybody knows it, including race | | | | engine will lose all responsiveness coming out of |
| officials. That's why almost every class has limits | | | | the turns. |
| on combustion-chamber volume and mandates | | | | Dial Your Carburetor |
| flat-top pistons to effectively limit compression. | | | | Few areas of a race engine can limit potential |
| So why is this a tip? Easy--make sure you are | | | | more than a poorly calibrated carburetor. It goes |
| pushing your compression limit on every cylinder. | | | | beyond just changing out the jets. An |
| If you aren't, you're leaving power on the | | | | out-of-the-box carb will work adequately, but to |
| assembly bench. Combustion chambers in stock | | | | really make sure it feeds just the right amounts |
| cylinder heads can vary by a couple of cc's for | | | | of air and fuel to the cylinders, it needs a lot of |
| several different reasons. They include core shift, | | | | TLC from a capable carb tuner. |
| valve seats cut to varying depths, or other | | | | The first thing a good carb tuner will do is |
| casting problems. Because engine builders want to | | | | blueprint the entire assembly. No matter how high |
| make sure their pieces are legal, the practice is to | | | | the factory's quality standards, a mass-produced |
| bring as many combustion chambers to the | | | | product will have limits on how tightly tolerances |
| minimum cc limit and leave the rest large. | | | | can be held. Because a carb tuner deals with each |
| Make power by maximizing the compression in | | | | carburetor on a case-by-case basis, he can dial in |
| every cylinder. Instead of being afraid to make a | | | | every piece exactly to the blueprints' specs--and |
| chamber too small, use a few tricks to open | | | | then some. |
| them back up in order to bring every chamber to | | | | Other areas where a good carb tuner will spend |
| maximum compression. If there are differences in | | | | some time is the carb's throats, making sure each |
| the volume of the combustion chambers, there | | | | flows to maximum velocity, and all four (or two, |
| are several options to even them out. You can | | | | if that is the case) flow identical numbers. The |
| deck the head on angle from side to side; then, | | | | boosters are also critically important. They must |
| once the chambers are too small, you can open | | | | be precisely located in the venturis in order to |
| them back up by dishing the valves as necessary. | | | | maximize signal without blocking flow too greatly. |
| If you are still pushing rule limits on cc or | | | | Finally, good gains can also be found by working |
| compression, cut slightly larger valve pockets in | | | | on the butterflies. They must shut completely, |
| the tops of the pistons. Finally, check your rules. | | | | yet still allow the right idle rpm in order for the |
| Some classes that don't normally allow any | | | | engine to have good torque from the low rpm. |
| grinding work on the heads will allow minor | | | | Minimize Your Mains |
| touchups to enlarge a problem cylinder. | | | | You can lower the friction between the rod mains |
| Roll 'Em Over | | | | on the crank and rod bearings by reducing the |
| If your rulebook allows roller cams, you should | | | | side diameter of the mains. The stock rod |
| definitely take advantage of it. Roller lifters allow | | | | journals on a Chevy 350 are 2.100 inches, but in |
| cam designers to push the ramp speed limits that | | | | Bowtie equipment, they are reduced to 2.000. |
| hold back engines controlled by flat-tappet cams. | | | | Aggressive engine builders have been pushing the |
| That alone translates into power with more | | | | limits in stock car racing engines to the 1.888 |
| aggressive cam profiles that open the valves | | | | Honda journal size. |
| quicker and keep them at the upper limits of the | | | | Reducing the size of the journal reduces the |
| lift zone longer. If you aren't allowed to use roller | | | | amount of bearing surface, which reduces the |
| cams, machine in the largest lifter bores possible. | | | | associated friction. Cutting a main down from |
| Larger-diameter flat-tappet lifters also allow more | | | | 2.100 to 1.888 may not sound like much, but |
| aggressive lobe ramps. | | | | multiply that eight times for all the connecting |
| There is also the friction factor. The roller lifters | | | | rods, then figure that times your average racing |
| greatly reduce parasitic losses associated with | | | | rpm. Now you get the picture. |
| driving the valvetrain. While we are freeing up | | | | Smaller bearings also have other benefits. They |
| horsepower by reducing friction, don't forget roller | | | | require less oil to lubricate properly. Everybody |
| rocker arms. These are common at mid-to-upper | | | | knows the oil pump is a big source of loss of |
| levels of racing. If you're racing in a Super Stock | | | | power to the rear wheels, so any chance you get |
| class, check to see what you're running. Good | | | | to dial down the oil pressure should be welcomed. |
| roller rockers can add as much as 10 hp at the | | | | A third benefit from this tip is that rod mains also |
| upper rpm limits. | | | | mean the big end of the rod can be smaller. We |
| Fake It | | | | are now talking less rotating weight and more |
| Synthetic means fake, but when it comes to | | | | clearance inside the block for stroker applications. |
| motor oil, the gains that can be made are real. | | | | The advantage here won't necessarily be big |
| You need mineral-based oil in a new engine in | | | | numbers on the dyno, but you will feel it on the |
| order to get the rings to set. After that, don't let | | | | track by how quickly the engine responds to the |
| anything except premium-blend synthetic oil get | | | | throttle. The reduction in rotating weight and |
| into your engine. Synthetic oils lubricate better at | | | | friction translates into an engine that will spin up |
| lower viscosities, hold up better against heat, | | | | with greater authority. |
| resist gumming up, and just plain work better. | | | | Electric Cool |
| Back- to-back tests on an engine dyna- mometer | | | | Ever go to the gym and see one of those |
| with an engine that has already been broken in | | | | stationary bicycles with the big fan for a wheel? |
| showed a 5hp gain in synthetic over mineral oil at | | | | The resistance of the fan pushing air around |
| the same weight. | | | | makes for a pretty good workout. Now, picture |
| The superior lubricating properties of synthetic | | | | that fan on the front of your engine. |
| motor oil will often allow you to move to a lower | | | | The energy required to turn the fan is the same |
| weight. But be careful here. Before changing | | | | thing a mechanical radiator fan is doing to your |
| weights of oil, be sure to check with your engine | | | | engine. Air may seem thin when you're sitting in |
| builder first. | | | | your La-Z-Boy watching Monday Night Football, |
| Most classes limit maximum displacement but say | | | | but at 7,000 rpm it's a viscous, power-robbing |
| little in the way of bore and stroke limits, so what | | | | syrup. Now imagine someone offered to put a |
| do you do? Many engine builders are pushing the | | | | second motor under your hood. You'd take it, |
| limits of big-bore, short-stroke engines. A race | | | | right? That's exactly what an electric radiator fan |
| engine is a big bundle of compromises; but, if | | | | is all about. |
| handled correctly, utilizing a bigger bore can have | | | | Electric radiator fans completely remove the task |
| several advantages. | | | | of pulling air through the radiator from your racing |
| First, a bigger bore helps reduce one of the | | | | engine. If the race is short and you can get away |
| biggest limitations in a two-valve engine: valve | | | | with using just the power from your battery, the |
| shrouding. Before the air/fuel mixture can move | | | | electric motors that power the fans are free |
| down into the bore, it has to move out to get | | | | energy. If you're competing in longer races and |
| around the valve. If it hits the cylinder wall as | | | | must use an alternator to keep your battery |
| soon as it moves past the valve, flow is limited. | | | | from going dead, you're still doing better than |
| It's better to have more room between the | | | | using a mechanical fan. |
| valve seat and the nearest obstruction. | | | | A secondary benefit of electric radiator fans is |
| Another advantage comes from shortening the | | | | they are generally more efficient. The fans mount |
| stroke. Because the piston travels a shorter | | | | directly to the radiator, and their close proximity |
| distance, piston speed in a short-stroke motor is | | | | to the unit means much more air is pulled through |
| slower at the same rpm. On the power stroke, | | | | the radiator instead of around it. This also means |
| this translates into the piston spending more time | | | | you don't need to build a fan box--which makes it |
| in the top inch or two of the bore--where power | | | | easier to get to the front of your engine while it's |
| is made. Shortening the piston travel also reduces | | | | in the car. Hey, that's not a power tip, but who |
| the area of cylinder wall that must be scrubbed | | | | can't use a few tips on saving time and energy? |
| by the ring package. Reducing the contact | | | | |