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Discussion Starter #1
Ok, this is a goofy question but maybe somebody can help me out. While the motor, 454 Mark IV based, was apart I lined it up at TDC for ease of installing the distributor etc. However, my friend "tested" the new mini torque starter and now I have no idea where the motor is. The aluminum timing cover has no timing pointer, I have to make one for it. The timing cover is on and the motor is in the sub frame. Taking it apart is the last resort. I put the motor on the compression stroke, both valves closed, piston coming up. So, is there a way to accurately determine TDC? Can you determine anything from the crank keyway? Can you measure rotations between a certain valve open and closed and divde by a magic number, anything?!?!?
 

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Make a piston stop tool out of an old spark plug. Then you can use it to find your TDC.
 

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Discussion Starter #3
But since the piston "floats" at TDC for a few degrees how do I get an accurate measurement?
 

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Couldn't he ball park it and then put a dial gauge on the #1 intake valve, slowly rotate it, get his figures and split the difference via the dial indicator and harmonic balacer? He would have to know his cam specs. But then how do you attach the timing scale to the cam cover? One must be 1. very sure where the drill is drilling 2. be extremely brave when drilling a hole into a timing chain cover.

alan
 

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Discussion Starter #6
I've just made an old big block timing tab "fit" by cutting and drilling a new hole. It's about where a stock tab would be but I'm unable to verify. It looks like stock and mounts using the cover bolts. I just plan on knowing where TDC is and if its not "0" on the tab just make a note of how much I need to compensate.

I don't know the cam specs. It's not stock by any stretch of the imagination. I hate messing with junk that was not built by me. This motor came in the car and was pretty stout so I left it alone. I didn't take the engine apart, I just cleaned it up and put on a new timing chain cover and oil pan as the old ones were pretty beat up. The inside of the motor was very fresh so I decided to run it till it gave up. It looks like its a 80ish 454 block, there are no numbers, so its been decked or it was a crate block. It has 66 396/427 closed chamber heads and that's just about all I know.

I've got it pretty close as I said by looking at the motor and valve train. But what I need is some math to determine true TDC if some exsists. If not I'll wing it but that's always asking for trouble.
 

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I have used a piston stop that I got from Jegs, I extend it down a bit, then rotate untill it stops, mark the balancer, then pull it, get the piston past, re install the piston stop to the exact same depth (I used blue locktight on mine), back the piston to the stop, Mark the balancer, then Top dead center is exactly between the two marks.
 

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I have used a piston stop that I got from Jegs, I extend it down a bit, then rotate untill it stops, mark the balancer, then pull it, get the piston past, re install the piston stop to the exact same depth (I used blue locktight on mine), back the piston to the stop, Mark the balancer, then Top dead center is exactly between the two marks.
Wouldn't it be easier to rotate the engine til the stop hits, mark the balance, and turn the engine around the other way until it stops again. Mark and measure to the middle. That's tdc

This way you do not have to try and get the stop in the same exact depth two times...

Anyways, search the forum or summit racing for piston stops.
 

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Wouldn't it be easier to rotate the engine til the stop hits, mark the balance, and turn the engine around the other way until it stops again. Mark and measure to the middle. That's tdc

This way you do not have to try and get the stop in the same exact depth two times...

Anyways, search the forum or summit racing for piston stops.
If its a flat tapet cam, and its already in, I dont like to spin it backwards. Not sure if it would hurt it or not, just always had in the back of my head "dont spin it backwards"
 

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If its a flat tapet cam, and its already in, I dont like to spin it backwards. Not sure if it would hurt it or not, just always had in the back of my head "dont spin it backwards"
Ya, I have no idea if its bad, but I have done it and besides its only 1 revolution. Actually less than one.

I suppose you could start with the engine just past tdc, thread the stop in and back it up a little til it hits and go forwards from there.
Im just a little to lazy to do that myself
 

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If its a flat tapet cam, and its already in, I dont like to spin it backwards. Not sure if it would hurt it or not, just always had in the back of my head "dont spin it backwards"
Rotating the engine by hand in either direction will have no effect on the cam lobe/lifter wear pattern.
 

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Rotating the engine by hand in either direction will have no effect on the cam lobe/lifter wear pattern.
X2.
And the piston stop method mentioned above- rotate forwarde until it stops, mark the balancer/ rotate backward until it stops, mark the balancer then find the exact middle of those two points is the correct way to do it. Thats how you baseline TDC when you degree a cam but usually with a degree wheel, You don't need one though.
 
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