99wssixm6

iTrader: (3)

I was thinking about this for the last few days. I purchased a used custom grind cam and I need to figure out how long of pushrods to get. I know the proper way is to use a pushrod length measuring tool but I was thinking about something else.

So based on nothing else changing but the cam:

Why can't I measure the base circle diameter of my new cam with a dial caliper or micrometer and compare it to the diam. of the stock cam.

Example:

If the stock cam measures 1.100 and the new cam measures 1.000 then I would take the .100 difference and divide it in half to receive a figure of .050 longer pushrod.

Has anyone every used this method. And if so has it worked?

Just an idea

vettenuts

iTrader: (4)

Yes, you can take that approach. However, the lower base circle and higher lift also changes how the rocker moves across the valve stem and that should be corrected first prior to determining pushrod length.

That is actually the approach that vendors used with the "stock 7.400" length. Actually, stock length is more like 7.385" and the smaller base circle is used to come up with 7.400" as the length to use after a cam swap.

The_Rizzle

iTrader: (4)

A longer/shorter pushrod won't change how the rocker sweeps unless you add shims under the rockers. You're just playing with lifter preload. I used the base circle measurement change to figure out my pushrod length change, along with head milling and head gasket thickness differences.

Sales2@Texas-speed

iTrader: (5)

Like vettenuts said, you could take that approach somewhat...but also, consider this: How do you know it had the right amount of preload with the old rockers? How do you know how much preload that was in order to know if you want to keep it the same or change it for more or less?