If you are taking the time to read this, then you have already spent or are about to spend some hard earned money on go-fast parts. I would not assume anything at this point about pushrod length. A pushrod that fits one engine may not necessarily work in another. If you are using a stock length pushrod, then I can assure you that the pushrod length is wrong.
There are a number of variables in determining the correct length pushrod for your engine. Pushrod length is influenced by many things: The deck height of the block, the type of cylinder head that is being used, the brand of rocker arm that is used, the camshaft base circle, the lifter height, the valve stem size, the thickness of the head gasket, the thickness of the guide plate, the height of the valve job relative to the deck of the cylinder head.
As you can now see, there can be many things that affect the pushrod length. SO PLEASE CHECK! And as a note, always use heat treated pushrods with guideplates.
Buy a checking pushrod. There are many types available. I would use the one from Competition Cams. I have used theirs in the past with the most accurate readings. I sell the Comp pushrod checker for $19.95 plus freight.
Now you can determine correct valve train geometry, and this is only accomplished with the right length pushrod. The correct pushrod length will produce correct valve train geometry. You know you have the right geometry when the rocker arm roller tip rolls from the intake side of the valve tip, across the center of the tip (at approximately mid-lift), to the exhaust side of the valve tip (at full lift) and back. I like there to be minimal run out when checking pushrod length. On an 11/32 stem valve, .075” (+/-) is a good area to stay within. Be sure that the wear pattern is centered on the stem of the valve.
Simply remove the pushrod checker and measure it for an overall length. I would set this up again and recheck myself. You just never know when you might have made a simple mistake.
A very long time ago when I was first starting out, I did not understand the importance of the proper length pushrods and rocker arm geometry. The more in depth the engine became, the more I realized how important this was. I have taken customer’s engines and done nothing more than fix pushrod length. We have seen 20 horsepower to 30 horsepower on more than one occasion. I cannot emphasize enough about checking and double checking for proper pushrod length and rocker arm geometry.
