How to Check Pushrod Length

Find your own pushrod length checker by clicking here. 

 It's a good idea to check pushrod length anytime that you are building an engine.  Machining processes such as having the block and heads decked can affect stock valve train geometry.  It is crucial that you have proper valve train geometry to ensure that your engine is performing properly.  Aftermarket products can also alter valve train geometry.  Checking pushrod length is relatively simple, but you do need an adjustable pushrod length checking tool.  I used one from Comp Cams.  This one is nice because it has a mark on it that indicates one full revolution, which is equivalent to .050" of length.

Also note that if you are running hydraulic lifters you need to either temporarily convert them to solid lifters, or buy a solid lifter to test the length.  The reason that you need to convert to a solid lifter is that hydraulic lifters have a spring in them that will compress slightly, giving you a false reading.  I chose to convert my lifters temporarily to a solid lifter.  The following pictures show how to convert a hydraulic lifter to a solid lifter.

You will need your lifter and a pair of small needle nose pliers to perform the conversion

Step one is to remove the retainer. 

After the retainer is removed the pushrod cup can be removed by simply turning the lifter upside down.

With the lifter still upside down shake it gently and the plunger and spring should come out.  If this does not happen, insert the needle nose pliers into the lifter.  Then spread the pliers apart to make contact with the sides of the plunger.  Now pull the plunger out.  If this doesn't work tap the lifter on a wooden surface until the plunger comes out.  Do not grip the outside of the plunger or the lifter with pliers.  This could ruin the surface and the lifter will not function properly.

Next remove the spring and set it off to the side.

Next stack washers up inside of the lifter and reinsert the plunger and the pushrod cup.  Then reinstall the retainer.  You will have to experiment with the number of washers needed.  If you out too many in the lifter you will not be able to reinstall the the retainer.  If you do not put enough in there will be a space between the pushrod cup and the retainer, which will give you a false reading.  When done correctly the pushrod cup should be tight up against the retainer clip so that there is no movement in the lifter.  You now have a solid lifter. 

Now you can properly check the pushrod length.  The following photographs illustrate how to do this.

This is the adjustable Comp Cams pushrod checker that I purchased.  They come in different sizes, so you need to know a rough estimate of how long of a pushrod that you need.  To estimate this find your stock pushrod length.  On this engine the stock length is 8.150, so I purchased a pushrod length checker with a range that started slightly below stock length and went up to slightly past my stock length.  In my case my Comp Cams pushrod length checker ranges from 7.800 to 8.800.

Next put your engine on top dead center on the #1 cylinder and insert the adjustable pushrod.  Start with the adjustable pushrod fully collapsed.

Take a dry erase marker and mark the entire tip of the valve.

Now set the rocker arm over the stud (At this point do not install the rocker arm nut).  Next unscrew the pushrod until the roller tip on the rocker is positioned just before the center of the valve stem.

Next install the rocker arm nut. 

Rotate the engine through 3 cycles of the valve.  Then remove the rocker arm and check the pattern on the end of the valve stem.  The pattern should be in the center of the valve stem.  This pattern is slightly over center indicating that the pushrod is too long.  Turn the pushrod one revolution (shorter in this case), and re-check the pattern using the same method as used previously.  Continue doing this until you get the pattern in the center of the valve stem.

The pattern should look something like this.  Once you get the proper pattern it is just a matter of reading the adjustable pushrod.  First remove the adjustable pushrod.  Then spin it the shortest distance to get the indicator marks aligned.  Now spin the pushrod closed, counting the number of revolutions that it takes to fully close the pushrod.  In the case of this engine it took seven revolutions of the pushrod.  Multiply the number of revolutions by .050.  .050x7=.350  Add that number to the shortest length of the pushrod. 7.800 + .350 = 8.150 (stock length).  Now order the appropriate length pushrods.