High lift cams and valve train.

[838]

What added measures need to be taken for the valve train when adding high lift (625-670 range) cams besides roller rockers. Clearances, rocker modifications etc??

[kd]

Corrected Geometry tops my list.  Good guides and valve stems properly fit and using good viton seals are next.  Valve springs will have to be well chosen to control the valves at higher rpm without being too aggressive / abusive. (I say this because it seems obvious they will be venturing into that range with those cam specs.     )

I am assuming you are not meaning clearance for the springs and rockers in rocker boxes and covers or centering the pushrods in the tubes to prevent contact.  If you do not use rocker lockers, it is however possible to center the rocker on the valve tip at mid arc at the same time as the pushrods by shifting the rocker stands before torquing them down.  IMO Doing these last rocker adjustments optimize the geometry,  efficiency and life of the valve train.

I would also say travel limited lifters are a consideration too.

All in all, choose a well known and highly competent head guru to guide you and do the work that you can't (we have a few here as sight supporting vendors  ). It will be money well spent and probably the largest contributor to the success of the build.

[838]

My only job during this would be the assembly phase. That was where I was wondering if there were any differences vs a cam under .600". Things that I would need to be aware of and account for during install. Cam chest clearance, if I go 1.725 rockers or roller rockers (or both), travel limiters? Basically stuff for the laymen like me who can follow basic instructions and torque bolts down to be aware of during the install. I'll leave the complex stuff to the head porter.

Thanks

[SP33DY]

My only job during this would be the assembly phase. That was where I was wondering if there were any differences vs a cam under .600". Things that I would need to be aware of and account for during install. Cam chest clearance, if I go 1.725 rockers or roller rockers (or both), travel limiters? Basically stuff for the laymen like me who can follow basic instructions and torque bolts down to be aware of during the install. I'll leave the complex stuff to the head porter.

Thanks

Make sure that your head porter knows that you intend to use 1.725 rockers. Then he can set the necessary spring height and the retainer to valve seal clearance.

[Don D]

As an installer nothing to do different. The head ported will relieve the covers for roller rockers and get the rest right.

[ThumperDeuce]

http://baisley.com/rocker_service.htm

[jsachs1]

With 1.725 rockers, be sure to check clearance at the push rod tubes and top covers. The difference between the 1.625 ratio, and the 1.725 ratio is from the center pivot to the push rod.
John

[Don D]

Agreed but Baisley extends the valve lever and reclocks the relationship between the two. Baisley corrected rockers are not to be used without correcting the stem protrusion. The end result is perpendicular rocker to stem and pushrod to rocker lever at mid-life.

[Ohio HD]

With 1.725 rockers, be sure to check clearance at the push rod tubes and top covers. The difference between the 1.625 ratio, and the 1.725 ratio is from the center pivot to the push rod.
John

   

[SB107]

Does seat width come into consideration when dealing with aggressive cams? I know it isn't valvetrain related but not too far off track...

[Don D]

In my opinion we go back to autoshop 201. In other words a reliable valve job has to have certain basics and narrow seats are enticing because it can add a flake or two more flow. This also leads to the seat angle discussion too. Is there a place for 50 or 55 degree seats?