KNOT-RIGHT

We are currently reassembling these 540's.
The valves are all new and the heads have been resurfaced.
cam crane 741 hydraulic roller.

I colored the valve tips on a cylinder with magic marker to check the roller rocker contact. It appears the contact area is approx.
1/16 of a inch in width across the entire tip, However it is not dead center of the valve tip. It is slightly towards the center of the motor. Would that mean it needs a longer pushrod or shorter? I Should just buy the darn pushrod lenth checker.

Am I spliting hairs or what ??


Please respond with suggestions.
Thank you in advance
Gerry

WETTE VETTE

Good timing on this post. I will be doing the same thing in a week or two. I already bought the adjustable push rods and will come up with the best length before ordering. I too would like to know what is the best scenario for valve train geometry. Is max lift supposed to be when the roller is contacting the center of the valve? Thanks for opinions!!

KNOT-RIGHT

Whaz up Wette?

I would imagine it should be centered at .50 lift
in my case it is not. more like .75max lift.


check this site.http://www.compcams.com/information/Products/Pushrods/

rmbuilder

If the contact patch is on the outside (exhaust side) a shorter pushrod is required. Conversely, a contact patch to the inlet side of the valve tip requires a longer pushrod.
The checking pushrod is simply adjusted and the contact patch rechecked until the correct length is established. This test can be conducted with hydraulic lifters, as negligible valve lift is lost even when rolling the motor over by hand. Taking the plugs out makes the whole task much easier.
There are opinions that centering the rocker contact patch on the valve stem centerline at mid valve lift is the correct method for determining the optimum pushrod length. The method only applies when and if the valve train geometry is correct. This means that the rocker arm lengths and stud placement and valve tip heights are all perfect. To illustrate this, think of the valve angle and the rocker stud angle. They are usually not the same. If a longer or shorter valve is installed, then the relationship of the valve tip to the rocker stud centerline has changed. Heads that have had multiple valve jobs or resurfacing can also see this relationship change. The rocker length (pivot to tip) remains unchanged, so the rocker contact patch will have to move off the valve centerline some particular distance for optimum geometry to be maintained.

The optimum length, for component longevity, is the length that will give the least rocker arm contact area on the valve stem and the narrowest wear pattern. This assures that the relationship is optimized and the rocker is positioned at the correct angle. This means that the optimum rocker tip contact point does not necessarily coincide with the valve stem centerline, and probably will not. A safe margin to strive for is about +/-.080" of the centerline of an 11/32 diameter valve stem. This means that no part of the wear pattern should be outside of this .160" wide envelope. As the pushrod length is changed, the pattern will change noticeably. As the geometry becomes closer to optimum, the pattern will get narrowest. If the narrowest pattern is too far from the valve stem centerline, then the valve to rocker relationship has to be changed. In this case, valve stem length will need to change.

Hope this helps,
Bob

KNOT-RIGHT

The marker is wiped clean approx .090 width.
However it is not in the center of the valve tip. more towards the intake ports.

I would say the roller contact begins approx 1/3 of the diamiter of the stem and then moves to approx the center of the stem at full lift. again leavin a .090 width margin.

Is this ok or should it be centered on the valve stem at 1/2 max lift of the cam.

I am assuming a shorter push rod by approx. .050
one problem that I might see happening.The closed position of the intake the rocker arm is only above the spring retainer by approx .065 Using a shorter push rod will close this distance.

the pushrods currently being used are 3/8 comp cams 7.950 and 3/8 8.900.

This is the ladder end of my winter project of installing blowers on these 540,s. I have had to install lower comp. pistons and all.

I droped the merlin cast iron heads off to the machinist to have the Iconnel valves, harden seats, new springs and everything else. He took one look at the original valves and said look see your push rods are off by approx .100 while its still out on the stands I would like to get it as close as possible.

thanks for your reply.
Gerry

KNOT-RIGHT

this is what it currently looks like.

what do you guys think???

KNOT-RIGHT

.150 longer gets me this

KNOT-RIGHT

Yes Sutphen30 I think its a keeper.

Trying to get Matt keizer on the phone now to get the custom lenths Just called his cell he.s tying his boat up in Key west. as we speek.

What Are we doing wrong up here in 25 degree weather.

rmbuilder

Gerry,
Looks great!
Bob

KNOT-RIGHT

Thanks for your help Bob
Took me a little while to understand your post. What I ended up doing was removing the pushrod and worked the rocker. Then I got it. I am also going to need the longer 1.9 studs
The longer rods have left me with hardly any threads.

Thanks to everyone who contributed.

Gerry