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05-24-2020, 07:32 PM | #1 |
Registered User
Join Date: Sep 2017
Location: Red Oak Iowa
Posts: 225
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Finding TDC Am I wrong?
Got into a discussion with some fellows about finding tdc to drop a distributor in on a small block. They were of the opinion you had to either physically see the piston at the top or somehow feel the air coming out of the spark plug hole. I have always just had the valve cover off and if the timing mark was on zero and both valves were closed on cylinder #1 you’re there. That’s the way I’ve always did it but then it’s not like I drop distributors in twice a week. They called BS and that I must have gotten lucky if it worked for me. Who’s right?
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05-24-2020, 08:00 PM | #2 |
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Join Date: Feb 2013
Location: central California
Posts: 2,726
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Re: Finding TDC Am I wrong?
You're right. The TDC mark goes around twice for each cycle of combustion. While turning the balancer you watch the intake valve open, then it goes shut and the mark lines up. Boom...TDC. if you keep turning, the exhaust valve opens and shuts and the mark comes around again.....not TDC.
Feeling the compression with your finger works too but is far easier with two people and of course negates the need to pop a valve cover. |
05-24-2020, 08:13 PM | #3 |
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Join Date: Jan 2011
Location: Hayes Va
Posts: 4,569
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Re: Finding TDC Am I wrong?
Both ways work. The finger on the hole is an easy way to do it with out taking anything apart. Here is my procedure. Hook up the remote start button, pull the number 1 plug, bump the motor over with a finger or a rubber plug on a stick and listen for air while looking at the timing mark. When it is up I drop in the distributor. This assumes the mark on the balancer is good. Finding true TDC is a entire different process.
Jimmy
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05-24-2020, 08:52 PM | #4 |
Who Changed This?
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,086
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Re: Finding TDC Am I wrong?
Back in the day, I had a whistle that screwed into the spark plug hole. When you came up on #1 plug, you were sure to know. ♪ Chirp! ♪
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~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
05-25-2020, 11:57 AM | #5 |
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Join Date: Sep 2017
Location: Red Oak Iowa
Posts: 225
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Re: Finding TDC Am I wrong?
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05-25-2020, 12:09 PM | #6 |
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Join Date: Aug 2009
Location: Bowser
Posts: 13,512
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Re: Finding TDC Am I wrong?
[QUOTE=Steeveedee;8745613]Back in the day, I had a whistle that screwed into the spark plug hole. When you came up on #1 plug, you were sure to know. ♪ Chirp! ♪[/QUOTE
You can make a whistle from an old spark plug. Just knock the porcelain off it and drill out the centre electrode. |
05-25-2020, 01:27 PM | #7 |
But Found Her 25yrs Later!
Join Date: Oct 2010
Location: Oregon City, Oregon
Posts: 10,468
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Re: Finding TDC Am I wrong?
After I know it's on the compression stroke by using one of the methods above, I put a length of coat hanger wire in the spark plug hole, and slowly turn the engine with a wrench on the balancer. Turn it back and forth watching the wire go up and down and then stopping when it is Dead Center at the Top.
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