how to determine push rod length

71roadster · 04-14-2003, 01:57 PM

I know one way is to smear a little grease or something on the valve tip and the cycle the engine a couple times to determine where on the valve tip the rocker tip lies, but how do you keep the lifter from collapsing? My new heads are installed and I dont want to pull one off and have the expense and delay of installing 'checker springs' in place of a couple valve springs. There must be another way.

Anyone?

Thanks
Chris

clem zahrobsky · 04-14-2003, 06:06 PM

put magic marker all over the valve stem tip and turn over the engine and the magic marker should be scrubbed off in the middle of the tip. use a solid lifter to do the checking. you can also get a moroso push rod checker at the speed shops and this little plastic item just slips over the stud and you follow the instructions on how to check the length

[Modified by clem zahrobsky, 5:06 PM 4/14/2003]

gkull · 04-17-2003, 02:22 AM

Chris we just did my buddies BBC Camero. We used the spark plug hole and air pressure with the spring removal tool. To pop the springs off. Then we removed the damper and inner spring to get the spring pressure way down for the checking and cam break in 25 minute period.

Refresh my memory on your setup. But the general rule is with stock valve lengths and standard base circle cams: under .520 lift with 1.5 or 1.6 rockers "Standard 7.800 push rods"

.520 - .590 standard length or .050 over with 1.5 rockers and .100 over with 1.6's

I have a bunch of lengths and I just installed one of each and rotated the motor. With sollids it's easier. Then just look at the side of the roller where it hits the valve stem tip. I could see that they were of center. I changed from a .930 small base circle to a 1.050. The difference should be a .120 from a previous setup. To me .100 is close enough. So that's what I bought.

The correct way is the tiney spring and the adjustable length checker. What if you had fairly heavy oil and you had the oil pump primer electric drill going. The lifters would be being filled some what?

71roadster · 04-17-2003, 05:12 PM

Well after talking to my engine builder and getting a scowl for suggesting testing with a solid lifter, he showed me his trick. And its really simple. With almost any range of mild high performance cam there will only be about .125 - .150 inches of movement of the rocker tip across the valve tip. So that means with the lifter on the base circle with 1/4 turn of lash the rocker tip should sit about .075 on the high side (manifold side) of the center of the valve stem. So thats what I was shooting for and came up with stock + .050 length. Checked it by making my own checker pushrod out of one of the old stockers and had the builder measure. Gonna fire it up this saturday!!!

Thanks for your suggestions fellas.

Chris