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With the intake manifold still installed, how can I find the base circle of the cam lobe of #1 cylinder without a dial indicator. SBC 350
 

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I assume you are looking to adjust or set valve lash. Below is a very simple method for any engine not just a Chevrolet.

First, keep in mind that the exhaust valve always opens first followed by the intake valve. Picture a "W" if you will for lobe layout of a camshaft....

To find the base circle of the intake intake lobe: Rotate engine in the standard rotation so the exhaust valve of that same cylinder just starts to open.

To find the base circle of the exhaust lobe: rotate engine following the intake of that same cylinder as it opens, moves over the nose and almost closes, that will be the base circle of the exhaust lobe.

Pretty simple and as you follow the valves you will start to see their relationships and the overlap period. Pretty cool stuff....
 

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Not adjusting valves , trying to check my push rod length and I need to find the base circle on the cam of any valve and check that push rod .
 

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Why don't you mark the top if the stem with a Sharpie and roll the engine a couple of turns and check there the rocker marks the stem?
If it marks below the center of the stem the PR is too long and vice-versa
 

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Assuming you have an adjustable pushrod for checking length, Put it in the #1 intake valve lifter. Then roll the engine around by the crank bolt until you feel the pushrod move up and then back down till it stops moving. Once it moves back down, you will be on the compression stroke. Continue to turn the crank clockwise, until the balancer hits TDC. Now you are on the base circle for both #1 valves.
 

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Not adjusting valves , trying to check my push rod length and I need to find the base circle on the cam of any valve and check that push rod .
Laser Red Nova, my reply above is the very method I use to find the base circle of the cam INCLUDING when I do rocker geometry or for whatever reason you need to be on the base circle. Your question has been answered....
 

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Mike - 74 Nova Baltimore, MD
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With the intake manifold still installed, how can I find the base circle of the cam lobe of #1 cylinder without a dial indicator. SBC 350
Are you asking how to determine the diameter of the cam's base circle (small base circle cam vs normal base circle cam)?

As previously stated by others... use a stock pushrod to check the contact pattern on the valve stem tip. If the contact pattern is in the center of the valve stem tip, the length of your pushrod is good for your setup.

If contact pattern is too high or too low, you will need to get an adjustable pushrod length checking tool to determine the correct pushrod length. Once you have adjusted the pushrod to obtain the correct pattern showing on the valve stem tip, you just measure the length of the pushrod. I used gear marking compound on the valve stem tip to show the contact pattern.
I used the adjustable push rod below for this purpose (normal base circle cam).
https://www.summitracing.com/parts/cca-7702-1

If you think you have a small base circle cam, you may need the following adjustable push rod length checker.
https://www.summitracing.com/parts/cca-7703-1
 

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I assume you are looking to adjust or set valve lash. Below is a very simple method for any engine not just a Chevrolet.

First, keep in mind that the exhaust valve always opens first followed by the intake valve. Picture a "W" if you will for lobe layout of a camshaft....

To find the base circle of the intake intake lobe: Rotate engine in the standard rotation so the exhaust valve of that same cylinder just starts to open.

To find the base circle of the exhaust lobe: rotate engine following the intake of that same cylinder as it opens, moves over the nose and almost closes, that will be the base circle of the exhaust lobe.

Pretty simple and as you follow the valves you will start to see their relationships and the overlap period. Pretty cool stuff....
Not adjusting valves , trying to check my push rod length and I need to find the base circle on the cam of any valve and check that push rod .

What Andrew posted will put you on the base circle of the cam, which is the same as if you are adjusting the valves, and checking for push rod length.

.
 

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Mike - 74 Nova Baltimore, MD
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As long as your rocker arms were properly adjusted when checking, the contact pattern shown on the valve stems looks pretty darn good to me.
 

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I second that. Looks to be right in the middle. And as previously stated hope your rocker arms are not offset to the left or right now that up and down is good.
 
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