Reply to "Engine Rebuild Questions"

I contacted PAC with the following:

"The lift of the hydraulic flat tappet cam I am using will be 0.568".

If my math is correct, using the 0.060"seats and +0.050" retainers that you recommend would put my valve closed (installed height) at 1.810" and the valve open at 1.242".

The chart on page 32 of your catalogue shows valve closed 98@1.880", valve open 315@1.300" max coil bind at 1.115" and a max lift of 0.600"

My question is: What is the maximum amount of spring compression before running the risk of coil bind? ie. If coil bind happens at 1.115" then is it safe to run the spring with a clearance of 0.060" or valve open at 1.175" or is it in fact 1.300" as stated on the chart.

This spring is a little week for my application at an installed height of 1.880" but is right on target at around 1.820". the open load at 1.242" is on target as well but if coil bind occurs at 1.280" (1.880"-0.600") or 1.300" then I am going to have big problem.

My thinking is that if coil bind happens at 1.115" and I require at least 0.060" clearance then I should be safe with the valve opening to 1.175".Is more clearance required?"

They responded with:

"You are correct. The spring does CB at 1.115" and you can run .06-.08" off of that number. You do not have to have open at 1.300"

Also You may want to look at a PAC-1218 beehive spring. This will go in at 1.800" with 130 seat and 310 open. Being that the chrome moly retainer for this spring is only 10g you would be saving a ton of weight."

Hope this helps