| rustedorrotting | -- 10-14-2022 @ 3:52 PM |
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I have a 1941 ford flathead with 13 inches of vacuum at idle and 175 pounds of compression per cylinder. To me this says CAM and maybe it has been stroked. It has Offenhauser finned aluminum heads an Edlebrock manifold with 3 94's, only the center one is operational. How do I determine the lift and overlap on the cam? there are no identifying marks on the front of the cam behind the distributor. The secondary carbs are blocked from air and fuel, so just for show for now. Any idea's
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| carcrazy | -- 10-14-2022 @ 6:02 PM |
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What is the elevation of your location? Manifold vacuum is dependent upon elevation. At sea level your vacuum reading should be about 19" at idle for a stock engine with no vacuum leaks. As you go up in altitude, your manifold vacuum will decrease. To determine the lift and overlap of the cam, remove the passenger side cylinder head, install a dial indicator on the top of #1 cylinder intake valve, a degree wheel on the front of the crankshaft pulley and a pointer on the front of the engine block. Zero the dial indicator with the crankshaft at TDC on the compression stroke and set your pointer to TDC on your degree wheel. Rotate the crankshaft clockwise by using a wrench on the nut or bolt that is at the center of the crankshaft holding the degree wheel to it - be sure the degree wheel does not move relative to the crankshaft. As you slowly rotate the crankshaft record the point (number of degrees) when the intake valve begins to move (open). Keep turning the crankshaft and record the point where the intake valve just closes. Next place the dial indicator on the top of the #1 cylinder exhaust valve and record the points where the valve begins to open and where it just closes. The amount of overlap is the number of degrees between when the intake valve opens and the exhaust valve closes. The valve lift will be measured directly on your dial indicator when it reaches its maximum reading provided you have it mounted inline or parallel to the the valve stem. The cam lobe lift will be the valve lift amount plus the valve clearance which can be measured between the tappet and the valve when the valve is fully closed. This process is time consuming but worth the work if you need this information. This message was edited by carcrazy on 10-14-22 @ 7:50 PM
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| rustedorrotting | -- 10-16-2022 @ 7:56 AM |
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I am in Michigan's northern lower peninsula, so no altitude problems. The best I could get was about 13. I have been a mechanic professionally since 1970, so I know a little bit, but these old cars can really teach you a few things.
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| rustedorrotting | -- 10-16-2022 @ 7:57 AM |
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thanks for the advice, that's what i will do.
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