Moloko
03-09-2003, 07:06 PM
From Fyrhwk1 on Hardforum. thought this was a pretty good explanation in case anyone was wondering.
"pushrod engines are much smaller, lighter and less complex, costs less to build and is easier to build, its more reliable simply because there are less parts. It's desireable in a performance aspect because of its simplicity, DOHC has over 3 times the friction and easily double the parasitic loss associated with moving the valvetrain, and with the advancments in head designs the 2V head can flow with the 4V in engines built for 6-7000 RPM.
Dohc is better because theres no pushrod and less distance from the cam lobe to the valvestem, theres more moving parts but those actually moving up & down are reduced, it has more high RPM potential because of this, and of course it typically supports twice as many valves. since small engines need to rev in order to be livable they need the higher RPM advantage of 3 & 4V heads. It really all depends on what you're building the motor for, 4V DOHC heads can work great on a low RPM motor and 2V pushrod can on a high RPM one, it's mostly in the setup."
"pushrod engines are much smaller, lighter and less complex, costs less to build and is easier to build, its more reliable simply because there are less parts. It's desireable in a performance aspect because of its simplicity, DOHC has over 3 times the friction and easily double the parasitic loss associated with moving the valvetrain, and with the advancments in head designs the 2V head can flow with the 4V in engines built for 6-7000 RPM.
Dohc is better because theres no pushrod and less distance from the cam lobe to the valvestem, theres more moving parts but those actually moving up & down are reduced, it has more high RPM potential because of this, and of course it typically supports twice as many valves. since small engines need to rev in order to be livable they need the higher RPM advantage of 3 & 4V heads. It really all depends on what you're building the motor for, 4V DOHC heads can work great on a low RPM motor and 2V pushrod can on a high RPM one, it's mostly in the setup."