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How to find true top dead center 

 

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 Post subject: How to find true top dead center
Posted: Mon Sep 08, 2014 4:15 pm 
Stock as a Rock
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Hi,

I have a 250 alloy head crossflow I am building and I need to find the true top dead center so as to degree cam in. I have the engine on stand with bottom end all assembled and cam shaft installed. I think I have a good idea but want to check first. what I think is to wind engine one way and watch piston reach top dead center , mark the balancer at time mark pointer then wind engine opposite way till it reaches top dead center and mark again at timing pointer. Then the true top dead should be exactly the center of the two marks. If somebody can tell me if this method is ok it would be great. I have not degreed a camshaft in before so any advice would help.

regards Darryl...

 

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 Post subject: Re: How to find true top dead center
Posted: Mon Sep 08, 2014 9:58 pm 
Fordmods Junkie
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dial gauge

similar method to what you are describing but instead of visually looking
you use the dial gauge to tell you where the piston stops

 

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 Post subject: Re: How to find true top dead center
Posted: Tue Sep 09, 2014 9:10 am 
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I haven't tried this myself, but have read that you can use a large bolt threaded into the spark plug hole to stop the piston just short of TDC. Rotate the crank CAREFULLY in each direction until it stops, mark the balancer, then find the mid-point between the marks.

 

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 Post subject: Re: How to find true top dead center
Posted: Tue Sep 09, 2014 1:58 pm 
Stock as a Rock
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Ok thanks guys that's a couple good ideas

 

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 Post subject: Re: How to find true top dead center
Posted: Tue Sep 09, 2014 6:54 pm 
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On the 6cyl I proved the balancer hadn't slipped by winding close to TDC... Dropping the valve onto the piction and running a dial indicator on top of that... Obviously if the piston is at the bottom you'll lose the valve but it worked great and I could see exactly where TDC was, my balancer had slipped about 3-5mm over it's life...

Cheers,
Tim

 

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 Post subject: Re: How to find true top dead center
Posted: Wed Sep 10, 2014 5:32 pm 
Stock as a Rock
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That's a pretty cool idea. I need to find top dead on my 351 Windsor with heads on. that is what I will try with that. My crossflow is only long motor so will use the dial indicator idea on top of piston for that one.

 

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 Post subject: Re: How to find true top dead center
Posted: Thu Sep 11, 2014 1:09 am 
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Use a dial indicator if you can get one.
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 Post subject: Re: How to find true top dead center
Posted: Sat Sep 13, 2014 11:56 pm 
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dial gauge - wind in direction of rotation until gauge stops moving and mark - continue in same direction until gauge starts to drop and mark -half way between these points is TDC - piece of stiff wire can be used thru plug hole but not as accurate
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