Basic modifications for newbies
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'''There are numerous sources of information to assist the untrained individual in the rebuilding or repairing of specific components of a vehicle, but there needs to be a place where he/she can learn what to do and what not to do in the modification of their vehicle(s). This article will attempt to fill in the blank spaces in their understanding concerning these modifications. | '''There are numerous sources of information to assist the untrained individual in the rebuilding or repairing of specific components of a vehicle, but there needs to be a place where he/she can learn what to do and what not to do in the modification of their vehicle(s). This article will attempt to fill in the blank spaces in their understanding concerning these modifications. | ||
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First things first. The cam must be matched to the static compression ratio of the motor. The OEM's have super computers that tell them exactly the timing points to be ground into the cam to match the c.r. and make power at the rpm's the public expects. This is usually idle to around 4,000 rpm's or a little higher. Any cam that you bolt into the motor will have an operating range of roughly 3,500 rpm's. In other words, it will be efficient from idle to 4,000 or 1,000 to 4,500 or 2,000 to 5,500 or 3,500 to 7,000 or whatever, depending on the valve opening and closing points ground into the cam when it is manufactured. It will also have a wide Lobe Separation Angle (max lift intake point after top dead center added to max lift exhaust point before top dead center and divided by 2) for good manifold vacuum to properly operate power brakes and other vacuum operated accessories and contribute to a smooth idle (Grandma doesn't want the motor going RUMPETY-RUMP when she's on the way to bingo). An OEM cam might be measured at 114 to 118 degrees LSA for instance. | First things first. The cam must be matched to the static compression ratio of the motor. The OEM's have super computers that tell them exactly the timing points to be ground into the cam to match the c.r. and make power at the rpm's the public expects. This is usually idle to around 4,000 rpm's or a little higher. Any cam that you bolt into the motor will have an operating range of roughly 3,500 rpm's. In other words, it will be efficient from idle to 4,000 or 1,000 to 4,500 or 2,000 to 5,500 or 3,500 to 7,000 or whatever, depending on the valve opening and closing points ground into the cam when it is manufactured. It will also have a wide Lobe Separation Angle (max lift intake point after top dead center added to max lift exhaust point before top dead center and divided by 2) for good manifold vacuum to properly operate power brakes and other vacuum operated accessories and contribute to a smooth idle (Grandma doesn't want the motor going RUMPETY-RUMP when she's on the way to bingo). An OEM cam might be measured at 114 to 118 degrees LSA for instance. | ||
| − | Now, the newbie comes along and decides that the motor needs more cam. In most cases, he has no idea what the static compression ratio of the motor is or the piston deck height or the squish clearance or anything else about the interior of the motor. All he knows is that he wants the RUMPETY-RUMP that he heard coming from the Super Comp motor he heard at the drag strip. What he may not know is that the motor in that car has upwards of fifteen to twenty thousand dollars invested in it and is maximized for racing. It idles like that because the cam has to be very aggressive to work with the 12.0:1 to 16.0:1 static compression ratio that is built into the motor. It may have been designed to make power from 4,500 to 8,000 rpm's for instance and will be coupled to a very loose torque converter that stalls at around 5,000 rpm's for instance. | + | Now, the newbie comes along and decides that the motor needs more cam. In most cases, he has no idea what the static compression ratio of the motor is or the piston deck height or the squish clearance or anything else about the interior of the motor. All he knows is that he wants the RUMPETY-RUMP that he heard coming from the Super Comp motor he heard at the drag strip or the hot rod down at the Sonic Drive In. What he may not know is that the motor in that Super Comp car has upwards of fifteen to twenty thousand dollars invested in it and is maximized for racing. It idles like that because the cam has to be very aggressive to work with the 12.0:1 to 16.0:1 static compression ratio that is built into the motor. It may have been designed to make power from 4,500 to 8,000 rpm's for instance and will be coupled to a very loose torque converter that stalls at around 5,000 rpm's for instance. As far as the hot rod down at the Sonic, that owner may have used a cam such as a Thumpr to get that sound and the car may not be as fast as it sounds. |
| − | I'm just throwing these numbers around to show you that the cam in the Super Comp motor will not work in your street-driven 350 Chevy. | + | I'm just throwing these numbers around to show you that the cam in the Super Comp motor will not work in your street-driven 350 Chevy. The Thumpr cam may work, but you may be able to make more horsepower and torque by matching the other motor characteristics to the proper camshaft and still have your rump-rump. |
I've gotten a little off track with my explanation. We need to go back to what a newbie should do to his vehicle FIRST. | I've gotten a little off track with my explanation. We need to go back to what a newbie should do to his vehicle FIRST. | ||
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