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Car was originally equipped with a 352. The person I bought it from thinks the previous owner before him installed a 390. After searching the net, is it true the only way to find out if its a 352 or 390 is to take the motor apart and measure the stroke and bore? or is there another way to tell what motor I have?
Thanks....
 

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Rotate the motor on TDC. This will place number one piston all the way up and number four all the way down. Pull number one and number four spark plugs. Using a stick, measure the distance to the piston in each cylinder from the same reference point. The difference between the measurements will give you the stroke. A 390 has a 3.784 inch stroke. The 352 has a 3.5 inch stroke.
 

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You can measure the stroke with a small diameter rod, such as a dowel or a welding rod. Pull #1 plug and move the crank to TDC. Insert rod and make a mark on the rod in conjuntction with a point of reference, such as the edge of the valve cover, or exhaust manifold flange. Then rotate the crank until you hit the bottom of the stroke and make the second mark. Then measure the distance between the two marks. 390 is 3.784 inches. 428, in the off chance you got one, is 3.984 inches. I don't have the measurements for 352 on hand.
 
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