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The crank has been turned since the timing gears were installed. The distributor is out of the engine. I still have to put the push rods in.

How do I determine if I am on 1 or 6 at TDC?

  • 1
    What's the engine? – Ben Oct 29 '16 at 3:05
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Excellent question, at present both pistons (1 and 6) are at Top Dead Centre. You will probably have noted this from the zero timing mark on the harmonic balancer (I assume this is fitted!).

Mate, you need to drop the pushrods into location for 1 and 6. Then move the crankshaft bolt backwards and forwards through about 20 degrees with a breaker bar and socket (this is moving the crank).

As you rock the crank back and forth, the set of pushrods that move alternately up and down are the cylinder that is "rocking" or just finished the exhaust stroke and commencing the inlet stroke. The set of pushrods that don't move are the cylinder that is about to fire, commencing the power stroke.

In answer to your question, you are at TDC for BOTH 1 and 6, however for timing / firing order setup, number one cylinder is the one that the pushrods need to be stationary (not rocking).

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You want the top of the compression stroke, so if you can put your finger (or thumb) on the spark plug hole of cylinder #1, you can run your piston up to top dead center. If you feel the air being pushed out, you are on the top of the compression stroke. Put your distributor in at this point where the rotor is pointing at the cylinder #1 terminal on the distributor. You'll still need to time the distributor, but you'll be close at this point.

EDIT: I just realized you said the push rods are out of it. You won't get any air out of spark plug hole without the pushrods in, or at least this won't give you TDC on the compression stroke. You'll be sucking air into and out of the spark plug hole for each travel of the piston.

If you have the timing cover off, the easiest way to tell if you have it at TDC on #1 cylinder for the compression stroke is to align the timing marks on the timing chain gears. (At least that's the way you'd do it for a SBC/BBC.)

  • @Paulster2 - I'm probably going to feel rather foolish when you translate, but what are SBC and BBC? – dlu Oct 31 '16 at 4:02
  • @dlu - SBC=Small Block Chevrolet (Gen I) ... BBC=Big Block Chevrolet – Pᴀᴜʟsᴛᴇʀ2 Oct 31 '16 at 4:05
  • @paulster2 - I don't feel so bad… – dlu Oct 31 '16 at 4:07
  • @dlu - it's kind of a SWAG on my part, as the OP really doesn't state which engine is being worked on. Could be Ford, Chrysler, or Chevy. – Pᴀᴜʟsᴛᴇʀ2 Oct 31 '16 at 4:09
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This is a pic of the rocker arm's thinking since had to perform this by myself!!! I put a plastic plug that fit fairly loose in #1 Cylinder and turned engine over slightly each time tell the #1 blew out that plug,,,Now if I'm on top dead center thinking the #6 cylinders valves should be all the way open or closed??But know It's going to fir the #8 after#1 So the #8 cylinder should be all the way down I suppose??? I don't know this is my first time rebuilding any engine for this matter from start to finish,,, But did just rebuild my Volkswagen 1600cc engine and tell ya what this gave me a challenge!!!! Completely different Story considering but the firing order was 1,4,3,2 Plus a very good learning experience....

  • If the OP doesn't have pushrods in, how does this work? It will suck/blow out of #1 everytime the piston goes up/down. – Pᴀᴜʟsᴛᴇʀ2 Jan 19 at 2:47

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