QuestionQUESTION: Hi!
I´ve been trying to find out what the differences between the 425,429,472 and the 500 engines are... Except for boar size.
I i only seem to find cams that fit the 425,472 and the 500 engine. Can realy figure out the differens...
ANSWER: Hi Mikko:
The Cadillac 429 was used in model years 1964 through 1967. Bore and Stroke 4.13 x 4.0 with 340 Horsepower. In 1968 Cadillac change to the 472 and the later 500 engines, Bore and Stroke 4.30 x 4.06 with 372 Horsepower. These engines was used in Buicks, Pontiac, Olds and Cadillacs, and the all used the new and improved Turbo 400 automatic tranny. Hope this helps.
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QUESTION: Thanks! Helped a lott!
Gott another one for you!
The 429 engine has forged or cast pistons?
I am doing a complete original rebuild of a 1966 Coupe Deville but i want to "modernize" some parts of the engine (like the cam,carb etc) so it will run smooth and maby a bit more fule efficient.
I´ve been "warned" to put is forged pistons in to that engine due to the lighter wight and possibility that the pistons change shape. Is there any truth behind these rumour´s?
Was reading another forum were one guye had used forged pistons and was now experiencing rattle in the engine. He then changed to CAST pistons (whit same bore size) and the noice was gone...
AnswerHi Mikko:
The article below may answer your question best. I've only used cast aluminum alloy. Hope this helps...
The Cast Piston
The cast aluminum alloy piston has perhaps the longer history. It took over for the original steel part during the internal combustion engine's early development. The cast piston is the most familiar piston type.
Casting Alloys
Early cast aluminum pistons were made with inferior alloys. The piston expanded dramatically, requiring a loose fit in the cylinder and resulting in noisy operation when cold. Harley-Davidson pistons once had steel ribs inside them to control this expansion. Since about the 1960s however, most cast pistons have been unstrutted. Their alloys have gained silicon, a material that gives the pistons natural lubricity and limits heat expansion. All modern pistons have silicon in them. However, cast pistons have historically had the most. Some of them have as much as 25 percent silicon by volume. Silicon does bring a disadvantage however. It makes the piston brittle. Dropping a modern cast piston will usually crack it, so the piston must be handled carefully.
Mass Efficiency
Probably the greatest benefit of the cast piston is the efficiency of its mass. The multiple-piece molds allow intricate contours inside and out, resulting in light weight, good expansion control, and predictable heat flow through the part. That is, the piston designer can plan in the specific thickness in each place in the part that is desired, to result in expansion at those places that is warranted. So predictable is the cast piston's heat in fact that race tuners view the undersides of the piston to gauge the combustion efficiency of the engine. In much the same way others read spark plug, they read the dark splotches under the crown.
Applications
The cast piston is however expensive to manufacture. Die casting is costly, because it requires huge machines that do very specific jobs, and can't be easily adapted to do more than one kind of job. The result is that the casting process for pistons is relegated to the large piston supplier. The downside is that the cast piston is often found only in OEM specified sizes and types. There aren't a lot of different cast pistons to chose from if you are modifying an engine. The upside of this situation is that since only large piston manufacturers can afford to make cast pistons, they are usually competently made. In fact, the cast piston generally typifies the best technology that the piston industry has to offer. However, this doesn't mean it's the best piston for every application.
The Forged Piston
The forged piston is a more recent development. It appeared first on high-powered two-stroke engines. These engines were made in low production numbers, and their performance and use resulted in frequent detonation. Both of these traits, as we'll see, made the forged piston a pretty good match for this application.
Forging Alloys
The earliest forged pistons were also made with poor alloys. In many cases however they were even worse than the alloys the cast pistons used, because when the cast piston finally got silicon, the forged piston did not. The same brittleness that makes the cast piston crack when bumped hard would have resulted in even larger defects had it been used in a forging. Consequently, during the time that the cast piston defined a piston's normal expansion rate, the forged piston was far behind the technology. The forged piston had to be fitted loose, which made it noisy and wasted power. Recently however, silicon has been introduced to the forged piston. A mixture of alloys has been found that together with silicon do not result in defective forgings. For example, nickel has been found to offset the silicon's tendency toward brittleness. However, not very much nickel can be used, as it is a heavy metal, and it affects the mixture in other ways. The result is that the modern forged piston is much more dimensionally stable than was true in the past.
Mass Efficiency
However, once again, the forged piston's mass does more to define its characteristics than does even its materials. The forged piston has historically had a crude interior shape. The forging ram is straight, which results in a rectangular rather than an inticate interior. There is too much mass there. Consequently, the forged piston has poor dimensional stability. Its expansion is not very controllable. Many engine builders overcome these two problems (too much weight, unpredictable expansion) at least partly by removing by hand the extra material inside the forged piston. This allows them to fit them tighter and rev them higher. However, many forged pistons also have overly thick skirts as well as unsophisticated interiors. This is because the forging produces a piston blank, remember, and not a finished piston. The piston wholesaler takes this blank, and from it, carves out several different sizes and shapes of pistons. If the piston being made happens to be the largest the blank supports, it ends up with the thickest skirt. While hand reworking (or CNC milling, as many do now) the forged piston can lighten it and make it behave more like an intricately made cast piston, there is still excess weight due to the thick skirt.
Applications
Unlike the cast piston, the forged piston is easy to manufacture. Smaller piston manufacturers therefore specialize in this piston type, even if some of them may not be as competent at making pistons as are the larger cast piston makers. Forged pistons have quickly become the choice of custom engine builders because they can be had very quickly, and in virtually any configuration desired. Moreover, the forged piston's added thickness is used by these builders to custom configure the piston even further. For example, flycuts on the piston's crown for high performance valve relief is an easy process with the forged piston. There's a lot of material there in which to do it, much more than there is in the cast piston. The forged piston was also the first piston type to adopt the modern ultra-thin piston ring, for the same reason. It could be done easily and immediately. There were no molds for such a piston among the cast piston manufacturers for at least a year afterward. This situation has resulted in the forged piston acquiring something of a high performance personna, even though its overall technology is less current than the cast piston's. Most of that reputation is unearned, but in at least one way it is in fact a reality. The forged piston is inherently stronger than the cast piston. Lower silicon content of course would result in this, making the forged piston less brittle. However, there is another reason as well. The forging process compresses the alloy's molecules, making the material more dense than a casting. The result is a piston that withstands the pounding of detonation better. This is why OEMs use the forged piston in two-strokes and turbocharged engines. Forged pistons are also included in many OEM high performance options kits for their street models.
Summary
To sum up, the cast piston is light and very dimensionally stable. It is found in high-rpm mass-produced engines that are not subject to modification or prone to detonation. The piston is however fairly brittle, and the cost of its manufacture has limited its availablity outside the OEM sources and applications. On the other hand, the forged piston is inherently heavy and less dimensionally stable. It is a good choice for engines in which detonation is probable, and its wide availability has made it the choice of engine modifiers. The special demands of these end users has given the forged piston its own niche in the powersports market. The next time someone tells you how superior one piston type is over another, tell them the truth. Because, as Paul Harvey likes to say, "Now you know the rest of the story." Hold the fries, please.
