stagger
Joined: 15 Nov 2004
Posts: 6
Location: Northwest
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 Posted: Mon Jan 31, 2005 4:07 am Post subject: NASCAR engines |
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I am interested in what Ford and Dodge are using for engines. What are the limits for engine size and carburation? I have not found much info in magazines or books on this subject. I suppose, racing being what it is, that there are many speed secrets involved in NASCAR.
Stagger |
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acegear
Moderator
Joined: 22 Oct 2004
Posts: 973
Location: Enumclaw, WA
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| Posted: Tue Feb 01, 2005 6:05 am Post subject: |
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As Stagger mentioned, NASCAR engines are a closely guarded secret. In the early years, "motors" were a combination of new, used, and scavanged parts put together in the barn for use the next weekend. Now engine builders have facilities rivaling that of the cleanest hospital, with the most exotic alloys available.
However, not withstanding these million dollar operations, the modern NASCAR engine is still based on a 1950's era design. And despite the variety of manufacturers that started in NASCAR, only three remain; Chevrolet, Ford, and more recently Dodge.
Each manufacterer supplies the block, clyinder heads, and intake manifolds to thier teams. From there it is open season on the other parts used in assembly, as long as it is within NASCAR rules of course. And while NASCAR has worked to keep the parity between the various manufacturers to a minimum there are still noticable differences.
The Chevrolet SB2 is a direct decendent of the 1955 265 cid small block. The main difference from the stock motor is the slight staggering of the lifter holes in the blocks gallery. This was done to give the new heads an offset for the valve's new locations and angles. Amongst other changes was the "dry" intake manifold. Where all previous Chevy motors bolted directly to the block and served as the top of the lifter gallery, this intake fastens only to the intake portion of the heads and a plate covers the lifter gallery. This has several advantages for racing that the stock set-up does not have. Since the intake removed from the hot oil the air/fuel mix is cooler, which is also helped by air being able to circulate under and around the intake. In addition, the new intake location does not require pulling the distributor and retiming the engine or draining the water from the engine since it is "dry".
With Dodge returning to NASCAR the first made-for-racing-only was also developed. Using the technology that is used to develop a "street" motor, the Dodge engine is based on the "P" used by Richard Petty after the "Hemi" design was banned from NASCAR in the 70's. This seventh-generation design was refined using stereo lithography which allowed the engineers to "see" the flow of air, water, oil, and fuel through out the engine and maximize the efficency in moving all these fluids through. Dodge immediately relaized the benefits of their design, when the new Dodge engine showed only a 3 degree difference in water temperature anywhere in the engine. This amazing reduction in "hot spots" makes for more consitent reliability and performance. In addition this Dodge engine also features a six bolt main, which is more than the standard four bolt main and adds more internal strength to the engine block.
Ford's NASCAR engine program is based on the Windsor 351 cid block. While the Cleveland 351 has also been used in the past, Ford went with the Windsor because it had less metal on the front of the block around the timing chain. This, in addition to the new "Siamese" method of cylinder casting in which the block's bores are formed in unison rather than separately, makes for a stronger and more stable block.
Another innovation comes from team owner and Ford engine builder Robert Yates. He modified the angle on the flat side of the heads and how they met the block. He also took the spark plugs and changed the angle in which they came into the heads, bringing them closer to the combustion chamber. These changes combined to lift the heads higher where they met the intake and also raising the tops of the ports. The flow from the carb to the valves was changed becoming more efficient, and with the ports being enlarged, flow also changed and increased to make the engine run better on race day. Of course all these changes required a new intake design that would bring all these features together.
One manufacturer that isn't in NASCAR yet but is in the Craftsman Truck Series is Toyota. Using their experience in open-wheel racing, they have transfered some of that engine know-how to thier truck program. Using a NASCAR-approved "wet-sleeving" construction, Toyota has developed an engine with more versitality than the other "domestic" brands.
"Wet Sleeves" have an advantage over the traditional sleeved engine in that the sleeve is easier to change if damaged, and does not affect the integrity of the block material. Traditional sleeving requires the sleeve to be machined slightly oversized then pressed into place while heating the block. This makes for a rather permanent installation. A "wet sleeve" however, has a lip on one end that is held in by the head. Machined to more matching tolerances the sleeve is installed in a normal temperature block and becomes more of a parts holder than an integeral fixture of the engine. An additional benefit is having more flexability for choosing bore and stroke combinations. While NASCAR rules do not allow more than 358 cid, many teams have been known to use a smaller bore and stroke combination to capitalize on a particular torque and power characteristic.
The bottom line is that NASCAR motors today are not your average "stock" engine. Run at over 10,000 rpms, with a 20:1 compression ratio, and 800 hp, all from 358 cid.
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A win is a win, and second place is never good enough |
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