Verschiedene Motor Tech Infos

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bin gerade über ein paar verschiedene Tech Infos gestolpert und dachte ich poste ein paar die mir interessant schienen.

Noise Complaints with 2004-2005 3.6L Cadillac Engines

If a whine, ringing or whistling noise is reported in several 3.6L Cadillac engines, replacement of the crankshaft harmonic balancer is recommended if noise is isolated to the front of engine and balancer is three-spoke design. Models affected include the 2004- 2005 Cadillac CTS and SRX; and 2005 Cadillac STS with 3.6L engine (VIN 7 - RPO LY7) and without heavy duty cooling (RPO V03tV92). Other complaints of a faint engine whine-type noise have been reported at speeds of 0-30 mph (0-48 km/h) at 1,000-2,500 rpm and may be caused by the primary camshaft drive chain. This type of noise may be amplified by the vehicle's body structure. Some installers/ customers may comment on a whine, whistle, or ringing type noise from the front of the engine that increases in intensity as engine rpm

increases. This noise is most audible standing in front of the vehicle with the hood opened. If the noise fades into the ambient engine noise by 2,000 rpm the harmonic balancer may be the culprit. Refer to Figure 5 and inspect the crankshaft harmonic balancer to determine the design type. If the vehicle was built with a three-spoke design crankshaft harmonic balancer, replace the harmonic balancer with a new unit (P/N 12597654.) However, if the vehicle is equipped with the V03N92 Heavy Duty Cooling package, DO NOT replace the six-spoke design crankshaft harmonic balancer (see Figure 6). Continue with routine diagnosis to isolate the noise.

Figure 5 Refer to the above graphic illustration and inspect the crankshaft harmonic balancer for design type. After the inspection, if the vehicle was built with three spoke (1) design crankshaft harmonic balancer, replace the harmonic balancer with p/n 12597654.

Cadillac 4.6L DOHC Aluminum Cylinder Head and Block Crack Cautions

Cadillac 4.6L DOHC engines may be prone to cracking of the aluminum block casting around the cast iron liner (Figure 8). Knowing that this possibility exists, make a close examination of the deck prior to doing any machining at all – and before you then spend numerous hours on cylinder head bolt repairs. The second tip involves cylinder head c/n 3533989 and 12554607, which would be the left head (or front, in the transverse mount engine) that has an alternator bracket bolted onto it in some applications. This head will always have the bosses for this mounting bracket but both of them may or may not be drilled (see Figure 9). If you want to avoid problems I recommend that you drill all of the bosses, thereby eliminating the possibility of having a warranty problem upon installation and also reducing head proliferation.

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Understanding Spark Plug Heat Range

Finding the right spark plugs for a modified engine is a little more involved than just looking in a catalog for make and model. Depending on the engine modifications you’ve made, you’ll need to take a few extra factors into consideration before settling on the right spark plugs (Figure 1). These factors include spark plug seat design, thread length and diameter, and reach. One of the most important – and least understood – factors in choosing aftermarket spark plugs is the heat range. Heat range is the speed at which a

spark plug can transfer heat from the firing tip to the cylinder head water jacket and into the cooling system. Choosing the right heat range is crucial for high performance engines. If the heat range is too cold, the spark plug will be unable to properly self-clean by burning off carbon deposits. If it the heat range is too hot, your engine could experience detonation, pre-ignition, or power loss. Most spark plug manufacturers recommend that the tip temperature remain between 900° F (500° C) and 1,500° F (850° C). Heat ranges are designated by each spark plug manufacturer with a number. In broad terms, spark plugs are often referred to as “hot plugs” or “cold plugs.” A cold plug has a shorter insulator nose length – the distance from tip to spark plug shell – and transfers heat rapidly from its firing tip to the cylinder head water jacket. Cold plugs are ideal for high rpm engines, forced induction applications, and other instances where the engine produces high operating temperatures. Conversely, hot plugs are good for applications that operate mainly at low rpms. Because they have a longer insulator nose length, heat is transferred from the firing tip to the cooling system at lower pace. This keeps the spark plug temperature high, which allows the plug to self clean and prevent fouling. Unfortunately, heat ange numbers are not universal – each brand has its own method for assigning heat ranges. You’ll need to talk with your sales rep or

consult with the manufacturer to find the best heat range for your application and spark plug brand. Be prepared to supply some basic vehicle information, including any modifications you’ve made. As a rule of thumb, you can expect to require one heat range colder than the factory-supplied plugs for every 75-100 horsepower you’ve added with your modifications, according to Champion

Spark Plugs. Here are some more basic guidelines to get you pointed in the right direction:

• Supercharging/turbocharging:

For-ced induction leads to increased cylinder pressure and temperature, which could lead to detonation. Depending on the exact application, you’ll need to go with a significantly colder heat range (faster heat transfer) over stock.

• Nitrous oxide:

The high cylinder temperatures caused by nitrous usually requires a colder heat range over the stock plug.

• Methanol:

Since it has a higher octane level than standard gasoline, methanol delivers more complete combustion. As a result, you’ll need a colder plug to transfer more heat from the combustion chamber.

• Increased compression ratio:

Higher compression ratios mean higher cylinder pressure and temperature. Once again, you’ll need a colder heat range to rapidly transfer all that extra heat to the cooling system.

• Air/fuel mixture modifications:

Lean air/fuel mixtures raise the operating temperature, along with the plug tip temperature, possibly causing knock or pre-ignition. Use a colder heat range for leaner air/fuel mixtures. Rich air/fuel mixtures can cause the plug temperature to dip, allowing carbon deposits to build up on the tip. Use a hotter heat range for rich air/fuel mixtures.

• Advanced ignition timing:

In general, advanced ignition timing will raise the spark plug temperature. In fact, NGK estimates an increase of 70° to 100° for every 10° advance in ignition timing. For this reason, you may need to go with a colder heat range to prevent knock or pre-ignition.

• Prolonged acceleration/high speed driving:

Frequent and drawnout acceleration and high-rpm driving raises combustion temperatures and generally requires a colder heat range.

Influence of Grooved Main Bearings on Engine Performance

Manufacturers are frequently asked what difference grooving makes. Various forms of main bearing grooving have been used over the years. It’s essential to understand that bearings depend on a film of oil to keep them separated from the shaft surface. This oil film is developed by shaft rotation. As the shaft rotates it pulls oil into the loaded area of the bearing and rides up on this film much like a tire hydroplaning on wet pavement. Grooving in a bearing acts like tread in a tire to break up the oil film. While you want your tires to grip the road, you don’t want your bearings to grip the shaft, so grooving is bad for maintaining an oil film. The primary eason for having any grooving in a main bearing is to provide oil to the connecting rods. Without rod bearings to feed, a simple oil hole would be sufficient to lubricate a main bearing. Many early engines used full grooved bearings and some even used multiple grooves. Those choices were based on what engineers knew at the time. As engine and bearing technology developed, the negative effect of grooving was recognized and bearing grooving was removed from modern lower main bearings. The result is in a thicker film of oil for the shaft to ride on. This provides a greater safety margin and improved bearing life. Upper main shells, which see lower loads than the lowers, and hence don’t apply the same load to the oil film, have retained a groove to supply the connecting rods with oil. In an effort to develop the best possible main bearing designs for high performance engines, manufacturers have investigated the effects of main bearing grooving on bearing performance. The graph (Figure 2) illustrates that a simple 180° groove in the upper main shell

is still the best overall design. While a slightly shorter groove of 140° provides a marginal gain, most of the benefit is to the upper hell, which doesn’t need improvement. On the other hand, extending the groove into the lower half, even as little as 20° at each parting line (220° in total), takes away from upper bearing performance without providing any benefit to the lower half. It’s also interesting to note that as groove length increases so does horsepower loss and peak oil film pressure, which is transmitted directly to the bearing.

Notes: You will still find some fullgrooved main sets offered for older engines where demand is low and the engineering cost to bring the sets to current standards is not warranted (bearings generally represent the technology of the time the engine was developed).

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Vacuum Check That Engine

With the advent of foreign castings, some less than stellar, it is important to be more critical than before during inspection. One ngine builder uses a large vacuum pump to vacuum check every engine’s water jacket before it leaves his shop. His pump pulls around 22 inches of vacuum. When it reaches that point he closes the valve to check for leaks. Some engine builders have found a few brand new castings to have porosity holes in them after they were torqued down. All of these heads were aluminum SB Chevy heads and were made overseas. These heads were “good” prior to proper installation. One a few occasions, brand new water pumps have been found to have leaking seals at the weep holes. Air is much less dense than water, so any small leaks are easy to find. With a vacuum

pump you can check all freeze plugs, galley plugs, intake and head gaskets (for sealing) and block and head castings. For a test, one engine builder drilled a .006? hole in a freeze plug – it failed miserably. He says he even used the pump as a “reverse” pressure tester on cylinder heads where he couldn’t find an external leak, but knew the head was bad. He says it’s sort of a “second opinion”

that confirmed his suspicions.