Finding TDC

[javapop]

Does the piston need to be at the top of plug #1 shaft (screwdriver at highest point) or at the bottom of shaft for TDC? This is on a 94 corolla.

[Bitter]

top dead center=TDC

[javapop]

Originally Posted by Bitter

top dead center=TDC

Thanks, thats what I thought. Is there a trick to rotation prior to locking down and putting everything back together? We actually had TDC, and the timing mark on zero, looking at these these instructions for the 4A-F Engine

8. Turn the crankshaft pulley and align its groove with the No. 1 timing belt cover. Check that the valve lifters on the No. 1 cylinder are loose. If not, turn the crankshaft pulley one complete revolution.

I know we lined up the timing mark at the bottom, and the camshaft pulley was aligned with the mark as well. It appears to be 180 off now, and running like that... wondering if I need to double check the valve lifters. Any further advise?

[PatrickGSR94]

Originally Posted by javapop

Thanks, thats what I thought. Is there a trick to rotation prior to locking down and putting everything back together? We actually had TDC, and the timing mark on zero, looking at these these instructions for the 4A-F Engine
I know we lined up the timing mark at the bottom, and the camshaft pulley was aligned with the mark as well. It appears to be 180 off now, and running like that... wondering if I need to double check the valve lifters. Any further advise?

With a 4-stroke engine, each piston reaches TDC twice during the combustion cycle - at the top of the compression stroke and the top of the exhaust stroke. When doing engine work, TDC on the #1 cylinder is always TDC on the compression stroke, when all valves on that cylinder are closed. That's why you should check the lifters/rocker arms on all 4 valves of that cylinder to make sure they're loose (not pressing on and opening any of the valves).

For the crankshaft, TDC is TDC. It's the head that's important that you get it to TDC on the compression stroke with all valves closed. If you're 180 deg. off then the exhaust valves will be open.