Adjustable Push Rod Tool

Adjustable Push Rod Tool

I will be using roller rockers. My block has been milled down 19 thousand. The head was polished. I need to know the length of my new push rods.

Does anyone know the correct adjustable tool I will need…
My stock push rod are about 8 inch if I measure from top of cup to ball tip…

I think they come in .020 undersized, so might be just about right for your needs.

Thank you JackFish

I found this one at Summit

I understand this question has a lot of gaps in it, but just wondering if anyone has already measured their rods and can me a heads up on which will work with the 200 ??

The proper length will be determined by what keeps the roller near the centerline of the valve stem. Because the rocker arm ratio is variable through its range of lift, center it at mid lift and than check to see how close that is during lift cycle.

Info on custom push rods here
http://www.cpgnation.com/forum/pushrod- ... -3084.html

Thank you bubba

This is what I’m going for.


I need a length that will give me a pattern similar to the white area you see in the picture of the valve stem top.

It is very difficult for me to get an accurate measurement from my stock pushrod. To me it looks as though it is somewhere around 8”. Depending where you take the measurement from.

My block has been machined down 19 thousand. This tells me I will need a shorter pushrod. There are a gillion adjustable pushrods out there.

I was just wondering if any member here has already bought an adjustable tool for a stock 200 and could tell me which adjustable tool I would need..

My thinking now is I will need this one..

The Adjustment Range is 6.800 in. to 7.800 in. The image illustration does not show it as a cup end but the claim is for a cup end. Guess a call is in order on this one...

But do you think my thinking is correct..

Think about the geometry a minute....unless you move the pivot point of the rocker up or down, your initial contact point on the valves will always be the same when the valve is closed on a shaft mounted rocker. The length of the pushrod makes no difference on the rocker to valve contact in this type of setup.

In order to move that rocker to valve contact point when the valve is closed, you would have to shim the rocker stands. With stud mounted roller rockers that you usually find on SBC and SBF heads, you are changing the geometry of the setup by moving the pivot point up or down, hence the rocker to valve contact point changes with pushrod length.

Also, the contact point of the roller is not going to stay centered during operation. As the rocker moves thru its arc, that roller will sweep across the tip, so usually they are set up to start just outside the center of the valve and end an equal distance on the other side. Pushrod length is critical to achieving this on a SBC or SBF because the pivot point moves ans the pushrod length changes. Not so with a shaft setup.

On typical shaft-mounted adjustable rockers the adjustment is done thru screwing a plunger up or down on the pushrod side. A .019" shave should be within the adjustment limit of your rockers, but you'll have to check. A hydraulic lifter is going to preloaded by .030 to as much as .100 inches.

Anyway, the bottom line is, on a shaft mounted rocker the only things you will effect with a longer or shorter pushrod is the location of the adjustment screw in relation to lifter preload. The rocker to valve tip relationship is unchanged unless you move the shaft pivot center.

Thank you Jack

On typical shaft-mounted adjustable rockers the adjustment is done thru screwing a plunger up or down on the pushrod side. A .019" shave should be within the adjustment limit of your rockers, but you'll have to check. A hydraulic lifter is going to preloaded by .030 to as much as .100 inches.

Thanks for bring me back into the world of Six.. It makes perfect since….
Now that I think about it.
So any unusual wear on the valve stem tip would indicate issues within the rocker arm assembly or valve guides and nothing to do with pushrod length..

Click to expand...

Anyway, the bottom line is, on a shaft mounted rocker the only things you will effect with a longer or shorter pushrod is the location of the adjustment screw in relation to lifter preload. The rocker to valve tip relationship is unchanged unless you move the shaft pivot center.

I wonder just how long it would have taken me to realize this while adjusting the rocker arms.. :mrgreen:

Click to expand...

So this would be a typical wear pattern..


And

This would be the considerations when selecting the correct push rod length.


This is my first adventure with cup style push rods. So I have taken 2 measurements as best I could.


I will order THIS tool.
It has a range from 7.2” to 8.3” Then I will find out for certain what will be the best length..

Thanks again big help
roy

MustangSix":1mb52qer said:

....The rocker to valve tip relationship is unchanged unless you move the shaft pivot center.

Click to expand...

Altering the length of the valve via resurfacing the tip or cutting new seats(valve head becomes more proud of the combustion chamber or more sunk in) will move the valve tip in reference to the shaft pivot center as well.

'68falconohio":3t0utvz8 said:

MustangSix":3t0utvz8 said:

....The rocker to valve tip relationship is unchanged unless you move the shaft pivot center.

Click to expand...

Altering the length of the valve via resurfacing the tip or cutting new seats(valve head becomes more proud of the combustion chamber or more sunk in) will move the valve tip in reference to the shaft pivot center as well.

Click to expand...

I forgot about that.. I was thinking by lowering the head to the block by milling the block .019 it would cause me to need shorter push rods.

When you referenced new seats, it lit a light bulb in my feeble memory..

I had new valves and new seats. So now it looks as though I will need longer push rods and not shorter..

OR
Maybe it will just be a wash...
Well one thing is certain, before I’m finished I will have the correct push rods..
Thanks "'68falconohio"

'68falconohio":38ho2f6s said:

MustangSix":38ho2f6s said:

....The rocker to valve tip relationship is unchanged unless you move the shaft pivot center.

Click to expand...

Altering the length of the valve via resurfacing the tip or cutting new seats(valve head becomes more proud of the combustion chamber or more sunk in) will move the valve tip in reference to the shaft pivot center as well.

Click to expand...

Good catch. You could add lash caps or grind the tips.