Confiming Crank TDC

[tibZ]

I have the head off my engine along with everything but the crank and pistons. Everything was set at TDC before removal. What I am wondering is as I was cleaning up everything I was assuming ( I know) that if I went 1 revolution the 1st piston was now on the exhaust stroke so I went another turn to be back on the firing stroke. Is this correct or does it not matter without the timing chain in place? It will be awhile before I start re-assembly but I was just wondering if this will be an issue. In other words, is there a difference when my #1 piston is at TDC on what stroke it is? I haven't removed the timing gear or oil pump gear from the crank. Thanks for any help.

Mike

[Carl Beck]

Yes it matters. Your distributor timing will be off. The rotor in the distributor turns once for every two turns of the crank.

Put the distributor back in - and look at the position the rotor is pointing to. If it's pointing to around 3:30 - you are one revolution off. If it's pointing to around 10:30 your at/near BTDC.

FWIW,

Carl B.

Edited December 26, 2008 by Carl Beck

[Galaxybj]

Do you still have the crank pulley on? If so, just turn it 'til the #1 cylinder is up and the 0 degree marker (the large "v" notch) on the crank pulley is lined up with the pointer.

[TomoHawk]

your at/near BTDC.

Carl,

What's BTDC? Or was that a typo?

[Carl Beck]

Hi Bill:

He said he still has the oil pump installed - the "0" notch on the crank pully will pass the pointer once, then return to "0" again - before the rotor returns to fire the #1 cylinder.

Just putting the "0" mark on the pointer is not enough to be certain that eveything is back where he started.. Turning the crank over once as he said he did, then again - SHOULD put him back were he was....but far better to be certain by verifying it with the rotor position.

Also -while he'd doing that - it is always good to assure that the pointer is correctly positioned. Put the piston in the #1 cylinder at its top dead center (just before it starts to go down again)... then check the pointer position in relation to the "0" mark on the crank - looking from were you would see it while using a timing light.

FWIW,

Carl B.

[Carl Beck]

TOMO - BTDC is Before Top Dead Center... your ignition is set to fire just Before Top Dead Center...

[tibZ]

Thanks for the replies.

I have the timing cover off so I can't put the distributor on. The crank pulley is 1 to 1 so the timing mark is always in the same position when the #1 cylinder is at the top. I guess I'll have to confirm my TDC when I start assembling, I was just wondering if there was another way to confirm it with everything off. Thanks again, Mike

[TomoHawk]

The reason I asked why you used BTDC is because TibZ wants to locate TDC for #1 on his engine. If you refer to TDC, then you need to say that or its equivalent, 0 degrees BTDC. Of course, the spark happens just before TDC, as in 5deg. BTDC, but it's a different thing then the actual TDC.

[beandip]

Here we go again. Carl , don't fall for Tomo's thing. He loves to argue.

[sblake01]

I also fell for it a few times in the past, but no more!

[Galaxybj]

"He said he still has the oil pump installed" Carl, I missed that - and I read it a couple times before I replied and looked like an idiot : -) I stand corrected.

[Diseazd]

I believe he said he had the oil pump gear installed (not the oil pump) and I assume when he said everything was off except the crank and pistons, that he means the front cover as well. The #1 piston should be at the top of it's stroke (crank key at 12:00) ,with crank sprocket timing mark at approximately 4:00.

Edited December 26, 2008 by Diseazd