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Unit 5302 · 03-11-2001, 02:39 PM

It depends on your application.

OHV generally makes more low end power. The reason being? Simple, since it's very hard to make a multivalve OHV engine, many times the head designs are more apt to focus on low end/midrange performance, say up to maybe, 5500rpms on a factory car. That usually means very good low end power, pulling force and solid midrange 3000-5000rpm performance. Going beyond 7000rpm on an OHV engine can also cause serious drivetrain problems. Valve float, bent pushrods and slop can cause serious engine damage. More stuff to go wrong, and it usually shows quickly when the engine isn't built to extreme tolerences. OHV engines are definately easier to work on, and they usually have a larger aftermarket catering to them, simply because they've been around since the 50's.

SOHC motors are much like OHV motors, except the improved drivetrain configuration eliminates some friction and makes them more rev happy. Due to the lack of multivalve heads they cannot really produce significantly more power than a comparable OHV motor, they are just better, as a genral rule, at running between 5000-7000rpm due to less chance of drivetrain failure. Manufacturer's usually take advantage of that property and design the heads a little more aggressive for higher rpm flow, making up for lost low end due to displacement losses. Usually due to increased external engine size associated in this configuration vs OHV the displacement drops somewhat versus previous OHV motors in the same chassis. The SOHC motors can be made to perform better than the OHV motor using their strength's which include, better drivetrain configuration, less moving componenets, reduced friction, and better head design to increase the output to a level exceeding or matching the previous OHV engine, but they generally sacrifice low end power due to smaller engine displacement.

DOHC motors are the ultimate in high performance applications. They allow for multi-valve setups which make huge flow rates easy to come by. The advantages to haveing more of the cylinder head availible to flow air is obvious, greater flow and huge increases in power. The DOHC motors are large, and they are generally heavy, many times this cuts down on their size, but they are extremely efficient especially when variable valvetrain technology is used, say like that in a DOHC 4.6L 32v V-8 found in the Mustang Cobra. The DOHC motor almost never makes solid low end power simply because they are designed for high rpm very high hp applications. I don't think you could find a DOHC motor made that doesn't run over 6000rpms, even the forced induction motors. They are very hard to work on compared to the OHV cousins, generally poor low rpm performers, very expensive, large externally, and heavy. Dispite this the power produced per cubic inch or liter can be completely out of proportion with the fallbacks.

03-11-2001, 02:39 PM	#2
Unit 5302 Registered Member Join Date: May 1999 Posts: 5,246	It depends on your application. OHV generally makes more low end power. The reason being? Simple, since it's very hard to make a multivalve OHV engine, many times the head designs are more apt to focus on low end/midrange performance, say up to maybe, 5500rpms on a factory car. That usually means very good low end power, pulling force and solid midrange 3000-5000rpm performance. Going beyond 7000rpm on an OHV engine can also cause serious drivetrain problems. Valve float, bent pushrods and slop can cause serious engine damage. More stuff to go wrong, and it usually shows quickly when the engine isn't built to extreme tolerences. OHV engines are definately easier to work on, and they usually have a larger aftermarket catering to them, simply because they've been around since the 50's. SOHC motors are much like OHV motors, except the improved drivetrain configuration eliminates some friction and makes them more rev happy. Due to the lack of multivalve heads they cannot really produce significantly more power than a comparable OHV motor, they are just better, as a genral rule, at running between 5000-7000rpm due to less chance of drivetrain failure. Manufacturer's usually take advantage of that property and design the heads a little more aggressive for higher rpm flow, making up for lost low end due to displacement losses. Usually due to increased external engine size associated in this configuration vs OHV the displacement drops somewhat versus previous OHV motors in the same chassis. The SOHC motors can be made to perform better than the OHV motor using their strength's which include, better drivetrain configuration, less moving componenets, reduced friction, and better head design to increase the output to a level exceeding or matching the previous OHV engine, but they generally sacrifice low end power due to smaller engine displacement. DOHC motors are the ultimate in high performance applications. They allow for multi-valve setups which make huge flow rates easy to come by. The advantages to haveing more of the cylinder head availible to flow air is obvious, greater flow and huge increases in power. The DOHC motors are large, and they are generally heavy, many times this cuts down on their size, but they are extremely efficient especially when variable valvetrain technology is used, say like that in a DOHC 4.6L 32v V-8 found in the Mustang Cobra. The DOHC motor almost never makes solid low end power simply because they are designed for high rpm very high hp applications. I don't think you could find a DOHC motor made that doesn't run over 6000rpms, even the forced induction motors. They are very hard to work on compared to the OHV cousins, generally poor low rpm performers, very expensive, large externally, and heavy. Dispite this the power produced per cubic inch or liter can be completely out of proportion with the fallbacks.