Many people agree with the phrase “there’s no replacement for displacement”. While technology can also accomplish this, having a larger displacement engine can produce a large gain. You may have heard of people saying, I went 60 or 30 over, on my engine’s bore. This is a machining process that is done to enlarge the engines bore to straighten worn out cylinders. While this is fun to say to your buddies it gives very little performance gain. The bore is usually kept as small as possible by your engine builder. Some engines have enough bore to hone out and could gain some power but most don’t. This is why more people are looking at stroking their engine. I would have to say that stroking engines first became popular with drag racers. This whole sport is centered on how much horsepower you can make. Many people were building big block engines then stroking them to make huge displacement engines. Companies then started realizing there was a demand and built several length crankshafts. Probably the most influential engine of all time, the chevy 350 smallblock, is a also a popular stroked engine.
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JDM engines stand for japanese domestic motors. Many import tuners have already changed to these engines. Many more sport compact enthuaists will look hard at purchasing these engines. Some people buy a jdm engine at rebuild time or simply to increase 10 or more horsepower, depending on the vehicle. JDM engines are generally tuned for a little more power than american engines. This is due to the company choosing to do so or emissions restrictions being tighter here. Most european cars are under the same stipulation. The jdm engines bought are usually used engines shipped over from main land japan with low miles. Beware as the condition of some of these engines may not be good. Purchase from someone reputable that stands behind the engine. Nothing is worse than spending the money to find out you have a bad engine in a month after installing.
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Troubleshooting engine problems can be a difficult task if you are not familiar with engines. Sometimes problems can be a combination of smaller problems or one problem normally not associated with the specific problem. If your car has not had a tune up in a while it’s always a good place to start. We will start with a generalized analysis and then try to narrow our search. If the car runs rough, jerks or surges as you press the gas more it may be an ignition problem. It may still feel smooth at low speeds or when pressing lightly on the gas. Start with the spark plug wires. Replace them if it’s been awhile (couple years or a lot of miles) or look for any arcing coming off of them. It is easiest to look for arcing at night time away from lights. Remember that a tiny little glow is all it takes to cause problems. Next remove your spark plugs and replace them if they look worn on the electrode corners. Also check or replace the distributor cap and rotor, all of these are part of an engine tune up.
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Four stroke valves are what allow air to flow in and out of the cylinder bore. The camshaft in a 4 stroke engine controls the timing of the air flow by the shape of the camshaft lobe. The height of the lobe dictates the lifting of the valves off their valve seats. Engines that spin high rpm’s can control valve float much easier when the valves are light. Valve float happens when the spring can no longer keep the lifter/valves in contact with the cam, power quickly drops off and the cam will be destroyed in a short amount of time.
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Carburetors or carbs were once commonly used on almost all car engines. Carbs come in all different types. The purpose of all carbs is simply to control the fuel going into the engine. The downdraft or draw through throttle plate carb was most widely used on passenger cars. These carbs usually consist of a low speed circuit used for low rpm or idle. Sometimes on the slightly more advanced carbs there are mid range circuits. The accelerator pump circuit assists in acceleration. The main jets are used the most and are very important to full throttle tuning. All production vehicle carbs (quadrajet, carter)usually have a choke circuit for warm up assist. Let’s start with the carburetor’s choke system. The choke operates usually by restricting the air into the engine. Along with changing the fuel to air ratio the manifold vacuum increases significantly, pulling even more fuel from the low speed circuit. The carb needs to run rich (alot of fuel) when the car first starts up because the engine isn’t warm enough to help vaporize the fuel. The carb uses idle, low speed or pilot jets (which are the same things) and air bleed screws to control the amount of fuel being sucked in at idle. The air bleed screws lean out the mixture as they are rotated out. Idle tends to be slightly richer than stoichiometric (perfect fuel to air ratio) of 14.7 to 1.
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EGR stands for exhaust gas recirculation. The EGR valve will generally make the car run poor at lower speeds or idle, but can effect it anywhere. The valve should not open at idle. Operate at midrange speeds and quit again before wide open throttle. The egr valve is usually located on the intake manifold or head. There is a diaphram in the egr valve. The valve uses manifold vacuum on the diaphram to lift or close a valve allowing exhaust gas to enter the intake manifold. An easy test for the diaphram is to remove the vacuum line that runs to the egr valve. You can normally reach the diaphram area with your finger. Move this opposite from the direction it normally sits at. Then cover the vacuum port located on the egr valve with a plugged hose or your finger. The diaphram should either stay in this other position or slowly move to the normal position. If it won’t hold vacuum and instantly returns to it’s origional position, either a vacuum port is still not plugged or the diaphram is leaking. If it is leaking replace the egr valve. If the egr valve holds vacuum then remove the valve from the manifold.
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The cam is a very critical part of an engines valvetrain. The cam is what lifts the valves into the combustion chamber allowing air to enter the cylinder. Cam profile selection is very critical on how an engine will run, and how log the cam will live. The cam along with the cylinder heads control how much air can enter the engine. The more air in the engine, the more power that can be made (within reason). This does not mean the most aggressive cam is the best one for you. You can get away with a fairly agressive cam on a carbureted vehicle. Be careful on a fuel injected engine as too much overlap will drop vacuum and will not allow the fuel injection to work correctly.
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