Determining correct pushrod length

[TIMS87GN]

Hey guys,
What is the correct method/formula for determining pushrod length? I want to get this right. I have a pushrod checker. My new combo is a 210/210 roller, Erson roller lifters, ported irons, Harland Sharp rockers and Felpro 9441pt head gaskets. Is it measured length + preload + compressed gasket thickness? I hope this will reduce valve train noise and improve performance. Thanks in advance!

 

[~JM~]

http://www.cpgnation.com/forum/threads/comp-cams-pushrod-tech.2408/

http://www.cpgnation.com/forum/threads/determining-proper-rocker-arm-geometry.4346/

http://www.cpgnation.com/forum/thre...eo-achieving-proper-rocker-arm-geometry.4490/

 

[earlbrown]

Don't try and do math to get pushrod length right.

Put the lifter on the base circle and the rocker in place with the adjustment screw 'middle of the road'. Then put an adjustable pushrod measuring tool in the spot then find the exact lentth between the rockers and the lifters.

Add whatever the lifter preload needs to be then with any luck that length will match up to a SBC length. (for example, my build uses SBC +.150" pushrods. I think a set of nice hardened 3-pc units cost me $18 shipped )

 

[turbofabricator]

I order custom pushrods for almost all builds from Smith Brothers. Great service and they have them to me with in 24 hours if I need them quick.
I also sometimes have to shim the rocker shafts up .016" with AN aluminum washers to get the rocker tip set right on the valve stem. There is a lot more to rocker geometry than push rod length. Stem highth will screw up geometry. It is the little details that can make a big difference. Rocker geometry can increase turning torque by more than 70ft lbs. on some engines. I read an interesting article by a top Pro-Stock builder many years ago on speedtalk.com exposing how just a few thousandths of an inch made so much difference in the torque required to turn an engine over by hand. Now keep in mind, they run more than 1.1" of valve lift and eleventeen hundred pounds of spring pressure. Our tiny engines with 130 lbs. of seat pressure ain't gonna pick up 70 lbs of turning torque. (Unless something is really wrong). But, making sure every little thing is right, pays off.