Checking P to V with Dial Indicator

[Rdobbs1977]

Never done this before but have been studying up a bit.

Is it ok to use the springs I have on my head (Dart Pro 1) as opposed to putting check springs on? A friend of mine had stated check springs can actually fool you and are not as accurate in using them.

Also, where the instructions speak to the point about 'pushing rocker down so valve makes contact with piston,' do I actually push down on the rocker or can i use my hand to push down on spring?

Lastly, I'll be using roller lifters so is it ok to use the roller lifter for this test? Thanks Bobby,

[techinspector1]

Years ago, I was thinking about this and decided to make a tool that I could use to do it. If you take an old rocker arm and grind part of one side of it away with your hand grinder, just a U-shaped relief, you will be able to mount the dial indicator stem to rest on the top of the retainer to take your reading and weld a nice long handle onto the top of the rocker arm, back by where the pushrod pocket is, so you will be able to adjust the nut on the stud. You can then pull on the handle and watch the dial indicator stem do its thing until you feel resistance, either with the valve head contacting the piston crown or with the valve spring pack stacked solid or with the rocker arm slot binding on the stud. Hopefully you have engineered the whole mess so that you will be contacting the piston with the valve head before any of the other stuff takes place. You might just want to begin with a long slot rocker or use your Xacto tool to grind the slot longer so that it will not present a problem. The longer the pull handle, the more jerk-free the operation will be. You can even put a bend in the handle so that it goes overhead and toward you a little.
Make certain the valve lobe for the valve you are checking is on its base circle, drop in a pushrod, making certain that it is on the pushrod cup, drop the ground rocker/handle assembly into place, install the ball and nut into place and take up the slack with the nut. Install the dial indicator with the stem sticking down through the "U" relief on the side of the rocker (make sure your "u" is wide enough so that it will not pinch the dial indicator stem as you conduct your operation and the rocker changes attitude) and zero the dial. Pull the handle down until you feel resistance and write it down. Write down the valve lift for that valve and subtract. There's your valve to piston clearance for that valve. Be careful if you have used a dual pattern cam, intake and exhaust lift could be different. I love doin' stuff at home for cheap, don't you?
Bada Bing, Bada Boom, over and out.

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[jerry clayton]

The contact or tight spot of valve to piston clearance will occur around 10 degrees before or after tdc as those are the areas where the pistons and valves are chasing each other----

Also the diameter of the valve to valve notch/position is critical------I like to use modeling clay on piston top and turn crank over two complete revolutions to sqush the model clay to shape-then with exacto or razor blade you can cut sections of clay away to measure or visually check the clearance---this will also show sqush area, dome to chamber, etc-----

I've just been working on 630 BBC for monster truck bash-should of taken pictures-----also of crank/rod/counterweight areas------