302
Lähetetty: 30 Elo 2006, 22:30
Mitä eroa on 302 2v 220hp:n ja Boss 302 4v 290hp:n koneessa? Onko vaan kaasari vai onko myös muita eroja?
Hieman enemmän on eroja tavallisen 302 2V koneen ja Boss 302 koneen välillä.Spiff kirjoitti:Mitä eroa on 302 2v 220hp:n ja Boss 302 4v 290hp:n koneessa? Onko vaan kaasari vai onko myös muita eroja?
Boss 302
After a very disappointing 1968 season blowing up the bottom ends of the Tunnel Port 302 engines, Ford designed a new engine specifically for F.I.A. Trans Am competition in 1969, the Boss 302. Introduced April 17, 1969, about 8,600 were built.
The block is essentially the next generation of 289 HP hardware, but features a forged steel crankshaft, 4-bolt main caps, and screw-in freeze plugs. These modifications were developed as part of the 302 Tunnel Port design. Street versions used connecting rods similar to the 289 HP while the Trans Am version used heavier 7/16" bolts.
The real magic of the Boss engines comes from the canted-valve Cleveland cylinder heads. While the Boss 302 is normally considered a 302 with Cleveland heads, these canted-valve heads were used first on the Boss before the rest of the Cleveland was developed. As fitted to the Boss, the heads feature steel spring seats, screw-in rocker studs, pushrod guide plates, and adjustable rocker arms. The Boss 302 and 351C-4V head casting are the same except for a minor difference in water passages. Camshafts were quite similar to the 289 HP. Due to the larger Cleveland-style heads, the Boss 302 weighs somewhat more than the normal 302, tipping the scales at 500 lbs.
The street version was conservatively rated at 290 HP @ 5800 RPM. During the '69 Trans Am season the racing engines were producing 470 bhp with a 9,000 rpm redline.
Designed for the road racing environment, the engines featured a scraper style windage tray. This tray attached to four special main cap bolts with small threaded holes in their heads.
Ford V-8 Small Block
221, 255, 260, 289, 289 HP, 302, 351W
Introduced with the 221 in 1962 for the Fairlane, this small block is Ford's first modern lightweight engine. The next was the 429 Big Block. Interestingly, 221 cubic inches was also the displacement of the very first Ford Flathead V-8, built in 1932.
A very compact design, the small block engine utilizes a thin-wall block casting not extended below the crankshaft centerline. Expanded to include the 260, 289, and 302, the engine family has provided power for most of Fords model lineup. Cylinder bore spacing is 4.38", the same as the Cleveland family. The small block is externally one of the smallest V-8 engines made, and total engine weight is around 460 lbs. The 289 was produced from 1963 to 1968.
In 1963 Ford released the 289 High Performance
which produced 271 BHP @ 6000 RPM.
The 289 HP features a high nodularity cast iron crankshaft, Brinell hardness tested to ensure quality. To prevent 4th order harmonic vibrations from destroying the crankshaft at higher RPM, a special vibration damper was used with an add-on counterweight within the timing cover. Somewhat stronger connecting rods with 3/8" bolts, thicker main bearing caps, solid lifter cam, screw-in rocker arm studs, machined valve spring seats, forged steel exhaust valves, a dual point mechanical advance distributor, and better flowing exhaust manifolds round out the package. Those fitted to Shebly GT 350 cars rated at 306 HP also featured a high rise aluminum intake manifold and Tri-Y headers.
In 1968, the 289 was stroked 1/8" to form the 302. Block deck height and piston compression height remained the same. Shorter connecting rods made up the difference in the stroke.
Some 302 blocks cast in Mexico have thicker, 289 HP style bearing caps. These were supposedly made with a higher nickel content alloy. Folklore claims these to be beefier than other blocks. On my bathroom scale a 1970 dated Mexican block weighed within 1/2 a pound of a regular 1970 302 block. That must be some lean beef.
Identified by casting numbers C8AM-B, 75ZY-AA, D1ZM-AA, among others, these blocks may be spotted by the "Hecho En Mexico" cast in the lifter valley. An extra unmachined boss protruding from the front of the driver's side cylinder bank can be easily spotted at the junkyard.
Small block reciprocating assemblies have some balance. The compact lightweight crankshaft itself does not carry enough counterweights to achieve zero balance. Extra counterweighting is cast into the flywheel and harmonic balancer bring the entire assembly into neutral balance. Early engines use 28.2 oz.-in. external balance, while 1982 and later engines use 50 oz.-in. flywheel and 34 oz.-in. damper external balance. All 351W engines use the early style 28.2 oz.-in. external balance.
Five different rocker arm alignment schemes have been used on small block engines.
289 engines built before mid-1966 and all 289 HiPer engines use a conventional stud mounted rocker arm. The rocker arm is held in alignment with the valve stem by a close tolerance pushrod slot machined into the cylinder head. These engines use hardened pushrods. This scheme is fully adjustable and may be used successfully with mechanical cams.
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Rail-type rocker arm with loose fit pushrod hole
289 engines built after mid-1966 and 302 engines use a rail-type rocker arm. These rocker arms have ears that extend downward, forming a rail or channel over the valve stem. This rail maintains proper alignment. The pushrod passes through a loose tolerance hole in the cylinder head, resulting in a cheaper assembly.
At high RPM, however, these rockers can jump the track, loosing alignment with the valve stem and resulting in potentially serious engine damage. These engines do not require hardened pushrods. This scheme was fully adjustable until 1970 when the studs were changed to incorporate a positive stop. The rocker arm nut is no longer used to adjust the valve clearance. Rather it is simply tightened down. Longer or shorter pushrods are selected to adjust the clearance. Since these are non-adjustable they can not be used with mechanical cams.
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Rocker arm with screw-in stud and pushrod guide plate
Most high performance applications will not work with rail type rockers. High valve spring loads and high RPM operation can pull the pressed-in rocker studs right out of the cylinder head. Some people have used roll-pins to hold the studs securely in the heads, but the best solution is to modify the heads to use screw-in rocker studs and stamped steel pushrod guide plates.
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Pedistal mount rocker arm
Later production small block engines use a stamped steel rocker arm with a cylindrical seat and fulcrum. The fulrum has a built-in pedistal and bolts down to the cylinder head. Small stamped steel rails, looking like channels, sit under pairs of pedistals and control their alignment. This scheme worked without guide plates or hardened pushrods.