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JSeery · 11-06-2015, 12:29 PM

Not if you truly want TDC. If you are just wanting a guess it would work. For a true TDC you need something to work as a hard stop as the piston comes up in the cylinder. When it is against the stop mark the position on the crank pully. Then reverse the rotation of the crank until it touches the stop again and mark that position on the crank. TDC is half way between the two marks. To be accurate repeat several times to get constant results. This is much easier with the head off!

Now, what are you needing TDC for? If you are just wanting the engine in position to mount a distributor your method should work fine. If you need true TDC, there are no short cuts that I know of.

11-06-2015, 12:29 PM	#3
JSeery Member Emeritus Join Date: Nov 2012 Location: Wichita KS Posts: 16,132	Re: how critical is TDC Not if you truly want TDC. If you are just wanting a guess it would work. For a true TDC you need something to work as a hard stop as the piston comes up in the cylinder. When it is against the stop mark the position on the crank pully. Then reverse the rotation of the crank until it touches the stop again and mark that position on the crank. TDC is half way between the two marks. To be accurate repeat several times to get constant results. This is much easier with the head off! Now, what are you needing TDC for? If you are just wanting the engine in position to mount a distributor your method should work fine. If you need true TDC, there are no short cuts that I know of. Last edited by JSeery; 11-06-2015 at 01:06 PM.