Push rod length calculation

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Aug 28, 2014 | 01:55 PM

2kgtp

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Push rod length calculation

What is the proper way to calculate pushrod lenght?? From all the reasearch i have done the stock cams base circle is 1.55" i purchased a cam that has a base circle of 1.386" intake, and 1.442" exhaust. Everything in the motor will be stock height as far as gasket thickness and heads not being milled. Slso using the stock lifters. I know the push rod checking tool is a good way to find pushrod length but the cam install will be done at a friends house and i cant leave the car there for more than a weekend. I need to be able to get the measurements close before install and then i can measure properly after the fact. Any input is appreciated.

Aug 28, 2014 | 06:35 PM

jp260z

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From: Norman OK

Pushrod Calculation

If your numbers are correct you will need 7.50" pushrods. Math is easy. Stock length (7.4") + .160/.110 (difference of base circle) = 7.56"/7.51"

Aug 28, 2014 | 10:46 PM

2kgtp

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Ok, i was under the impression that you divide base circle diff by 2.

Aug 29, 2014 | 07:48 AM

vettenuts

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From: Little Rhody

Based on your numbers, if you average the new base circle and subtract from the stock, then add that value to the stock length, it looks like 7.450" should work.

That pushrod is getting pretty long, I would consider larger OD pushrods like 11/32".