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98SteedaGT · 04-24-2002, 09:28 AM

A pushrod type engine works like this:

A cam sits in a valley in the center of the engine, it's driven by a chain from the crank shaft. This cam rotates with the engine. Directly on top of the cam are something called lifters, these can be Solid, Hydraulic or Roller. This is what transfers the lift from the lobes of the cam to a device called pushrods. Pushrods are long slender pieces of metal that are seated on top of the lifters, and as the lifters rise and fall this causes the rod to push or relase on Rocker Arms. Rocker arms can be Pedestal or Stud mounted, they also make a lot of different types, (like Roller), these rocker arms do just that, they rock back and forth exerting pressure on the top of the valve stem where the springs are. This in turn causes the valves to open and close. This all works together with Cam Timing to provide the 4 cycles of a normal car engine. Intake, Compression, Power, Exhaust (or however you say it).

An overhead type engine works like this:

There is no cam valley in the engine block, there are not lifters (at least, not like the pushrod types) The cams (2 or 4) in GTs sit directly above the valve stems/springs on top of the cylinder heads (if you notice, these heads will look a lot different at the cover, making room for the Cam Sprockets in front). These cams are linked to the engine the same as the other style, via chain or belt, but there are now two timing chains on the engine (one for each bank -left-right). These chains go to sprockets on the heads that in turn rotate the cams, the lobes on the cam push directly on to the valved themselves. This frees up some HP because the force isn't having to travel up the cam valley, through the lifters, up the rods, then to rocker arms, and then to the valves. It just goes straight to them. The 4V engines work the same, but have a main cam sprocket in front, then two smaller sprockets directly behind that link the two cams together. This is how they get the cams sync'd to each other.

If I have left anything out, someone fill it in for me.

04-24-2002, 09:28 AM	#6
98SteedaGT Registered Member Join Date: Jan 2002 Location: Texas Posts: 330	A pushrod type engine works like this: A cam sits in a valley in the center of the engine, it's driven by a chain from the crank shaft. This cam rotates with the engine. Directly on top of the cam are something called lifters, these can be Solid, Hydraulic or Roller. This is what transfers the lift from the lobes of the cam to a device called pushrods. Pushrods are long slender pieces of metal that are seated on top of the lifters, and as the lifters rise and fall this causes the rod to push or relase on Rocker Arms. Rocker arms can be Pedestal or Stud mounted, they also make a lot of different types, (like Roller), these rocker arms do just that, they rock back and forth exerting pressure on the top of the valve stem where the springs are. This in turn causes the valves to open and close. This all works together with Cam Timing to provide the 4 cycles of a normal car engine. Intake, Compression, Power, Exhaust (or however you say it). An overhead type engine works like this: There is no cam valley in the engine block, there are not lifters (at least, not like the pushrod types) The cams (2 or 4) in GTs sit directly above the valve stems/springs on top of the cylinder heads (if you notice, these heads will look a lot different at the cover, making room for the Cam Sprockets in front). These cams are linked to the engine the same as the other style, via chain or belt, but there are now two timing chains on the engine (one for each bank -left-right). These chains go to sprockets on the heads that in turn rotate the cams, the lobes on the cam push directly on to the valved themselves. This frees up some HP because the force isn't having to travel up the cam valley, through the lifters, up the rods, then to rocker arms, and then to the valves. It just goes straight to them. The 4V engines work the same, but have a main cam sprocket in front, then two smaller sprockets directly behind that link the two cams together. This is how they get the cams sync'd to each other. If I have left anything out, someone fill it in for me. __________________ // 1998 GT-Steeda Conversion \\ -- Sold // Now own 2001 F-150 SuperCrew 5.4L \\