Pushrod length

Since the cam swap the Cordoba runs well but I couldn't get it out of my mind that it should be better. After doing some research I have determined that I probably have the wrong pushrods (stock length), CompCams recommends pushrods that are .040 longer.

I have an adjustable pushrod but don't have a solid lifter and don't want to pull the intake. Can I determine the correct length by getting the cam on the base circle adjusting the pushrod until it's snug (won't move up and down and difficult to rotate) then adding .040 (the recommended preload) to the measured length?

From your post I'm assuming you have a hydraulic camshaft. If your present pushrods are too short. They will rattle like a solid lifter engine.

I would normally agree but have to point out that with even a mininal amount of lifter preload (.001) they would be tight enough not to rattle BUT I'd still be sacrificing some lift (up .040 of lobe lift) and duration. One site I found suggests a rule of thumb that .004 inches of loat lift equals 2-degrees of duration.

Using this information my XE274H cam (advertised at .488 and 230 degrees @.050 INT and .491 and 236 EXH with 1.5 rockers at the valves) could effectively be acting like a much smaller cam (.427 and 210 degrees @.050 INT and .430 and 216 EXH).

The graph that comes up when I use this info on their CamQuest software come up with numbers that mirror the graph I got with the dyno run.

I now understand your concern. This has also been a question of mine when using a non adjustable set up.

How about shimming the rockers up .010" at a time until it gets noisy.

If you re-think that you will find that if it were true you would have valves hung open .040 on the base circle. If the lifter was pumped up solid and you had zero lash, the cam will lift the valve the full distance. The only thing not running full pre-load will do IMHO is give you some clatter on startup while the lifters pump up to zero lash again.

Kevin

I finally got the car back from the painter and checked the pushrod length. After very carefully measuring everything I found just what I suspected, the stockers are too short. Funny thing though is when I put everything back so I could order the new pushrods I noticed that I could "wiggle" the rocker. I measured and found the lash to be .015, so much for the .040 preload.

BTW if you have none sdjustable stamped rockers and the push rod is not bottoming the lifter plunger you will be fine.
That is the reason for hydrauulic lifters, less mainainance and alot of forgiveness.

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How about shimming the rockers up .010" at a time until it gets noisy.

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Let's not go through this BS again. That is not what shims are for.