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Author Topic:   valve lenght
posted November 16, 2004 06:08 PM
Could some one explane this to me I see A lot of valve makes with like.100 lenght increase and the same with pushrods. What is the performance gane I;m guessing its a geometry thing but how does a person know what they need to do..

thanks for any ideas on this

posted November 16, 2004 07:40 PM
longer valves and pushrods are mostly for running valve springs with much taller installed heights. this is the way most stout double and almost all triple springs are. its only needed with high lift cams like rollers.


posted November 16, 2004 07:49 PM           
longer valves, or special retainers or locks, can give you more installed height for your springs.

longer pushrods are almost allways needed, once I bought a pushrod length checker for about 12 bucks in 1998 and started checking. Ive never assembled a motor yet that stock length pushrods were the correct ones for it.

I keep .050,.100,.150,.200 on my shelf to trial fit and assure the correct length. .200 have had to be on all the motors Ive built with small base cams.

posted November 17, 2004 08:21 AM
Also, higher installed spring hieghts (Longer valves are needed when you make the installed spring hieght higher than stock) are needed when you run higher lift cams. .600 to .800 inch lifts and larger you have to check for coil bind on the springs (the reason for a higher installed spring hieght, aka more movement) and then adjust accordingly, pushrod lengths etc.

Not sure if there is a perforamce gain per say, but the wrong parts can fail and or hurt performance. I think comp cams has a tech article showing how to determine the correct length pushrods if you want to look for it, to learn more about it.

Most cam manufacturers make it easy now days to select the proper components for there cams, and what to check for during installation, including springs, pushrods, retainers & keepers.