Thread: How to find TDC

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Okay, am almost done with a restore and engine swap. I am putting a 350 in place of a I6. I bought a rebuilt engine from a guy and I need to hook up the plug wires. My problem is I am not sure where #1 is on my HEI. I checked the 305 I have in my Jeep and went off that but it is obviously not right for this engine.

II know I need to find TDC for the #1 and that will tell me where it is on the distributor, Correct? What is the best way to find TDC for the #1 cylinder?

Thanks in advance, Dan

The short answer is it's anywhere you want it.

The long answer is:

Put the engine at top dead center, line up the timing mark on the crank with the timing pointer/label, then pull the valve cover and make sure both the valves on #1 are closed. (uncompressed).
If a valve is open rotate the engine another revolution and check the valves again.

The distributer will fire the coil everytime all those pointy things line up. The spark is distributed to the plug the ROTOR is pointed at. So if you pull the cap (now that the engine is at TDC, where that rotor is pointing is #1!

If you don't like it, you can pull the distributor out dink around a little until the distributor goes back in with the rotor pointing where you want it.

Ask if you are going to do this as there are a few tips more for doing that.

If ya really want to know, exactly, break all the porcelain out of a sparkplug, and slide a 1/4" rod thru the center untill it extends about 1 1/4" past the plug nose then weld it. Dont put it in yet---remove Number 1 plug (front of engine drivers side), stick your finger over plug hole, and bump the engine with starter (coil wire disconnected) untill you feel it trying to blow your finger off the plug hole. Stop---at that point it is coming up on compression on number 1. Remove the rest of the plugs, screw the "piston stop" which you made into #1 plug hole, put a 5/8" socket on the front crank bolt that holds the harmonic balancer , and turn it by hand in the same direction that it would normally turn when the engine was running. When it won't turn any farther because the piston has contacted the piston stop, scribe a line on the balancer directly in line with the timing pointer or some other mark that isn't going to move. Then rotate the engine in the opposite direction untill it stops against the piston stop again, and scribe another mark on the harmonic balancer, in line with the same pointer. Get out your tape measure and wrap it around the harmonic balancer between the marks. Exactly 1/2 way between the 2 scribed lines is your exact dead center, in relation to the pointer that was used as a stationary witness mark. Then quickly, before you forget, remove the piston stop and put it away---if you forget and fire your engine with it installed, your engine is toast..

Check this site out, hope it helps you.

http://www.hotrod.com/techarticles/51124/

~ Vegas ~

brian: Nice description man. I always wondered how to nail TDC.

That's nice. You can trade pulling a valve cover for pulling plugs. Whichever is easier. Course the method I mentioned requires that the timing marks are in the right places.

Go to www.summitracing.com and do a search for "piston stop". There are several to choose from. I used to use the gutted spark plug trick too until I found out the stops were available for cheap commercially. It makes a nice addition to your toolbox. While you're at it, get the one that works with the heads removed too.