Thread: Rocker ratio/duration

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"if any one thinks all this stuff is bolt on has alot to learn"

Bolts right on is a favorite of mine, tell folks it is an industry inside joke. The eyes then glaze and off they go, still thinking the same.

After all they saw it on TV, what would I know about anything

As someone whom has been boning up on his math skills ( going back to school @ 45 )
ZERO IS ZERO.

The valve physically cannot open sooner, nor close later. Ok, maybe later, at high rpm due to valve float.

Mechanically speaking, you ARE increasing load on the lobe, lifter, pushrod, rocker arm. Increasing lift will increase spring bind.

Now. What the AIR is doing is beyond mere plus one-minus one calculation. That an increased ratio will affect the effective duration is tantalizing!

IMO Tech made the only point that matters early on in this discussion. No one's arguing that increasing the rocker arm ratio will yield a larger volume of air/fuel charge, and that the larger volume of flow may yield a small gain in peak HP, estimated early on to be in the 10-12HP range. But as Tech stated before, for the average guy doing an engine for the street that extra ten to twelve HP is really insignificant. Considering that overall HP may be in the 400+ range it won't be a "seat of the pants" change that's worth the increased stresses on the valve train, and perhaps even a decrease in reliability. What makes more sense for most of the guys asking here is a nice torque curve that comes in early (good cruise power) and runs flat almost to redline. Having a few extra horses at one point on the HP curve is just a number. Sure, you can find all kinds of discussions on the net from the street racer crowd and the young guns who don't really care much about reliability but worship every potential increase in HP, but for those who are building a driver, wanting decent power and economy, but demanding reliability, chasing the HP increase of a taller rocker arm ratio may not make good sense. We're all entitled to our opinions, and if you don't agree that's OK, but recognize the audience.

many guys are going to do the job one time even the guys that plays with bigger engines very few want to buy new rockers... honestly i never check a engine at valve lift then use the same brand rocker for a bigger ratio for how much gain in dur. its much like the lifter bore size i know it can move it lash can play in to this . i have moved up to a bigger rocker ratio when no more lift could be on cam core for cam bearing bore size to get the lift i wanted to see yes it happens and some guys do not want the 60+mm cam core price. i have no magic control over customers to get them to do some things as it seems every one has a budget to work with . but i have ran threw more then one brand rockers on a test engine rocker arms and played with the push rod lengths . that why i ask if any one as check net lift and check cam lift in block. i do most every engine on the big stuff see abit more lift then what is on cam card but there some deflection in the real world . most all the time some more lift is not a bad deal then i move on to check piston to valve if i have that i call it a day and use the cam as a new custom grind cam not going to happen. there alot to this as how the rockers stand sets on head were the valve is in the head were the center line of rocker is and the size roller tip on rocker on and on and if the rocker arms is really the ratio its stamp on it