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  #61  
Old 07-22-2011, 02:32 PM
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Quote:
Originally Posted by leathermang View Post
WHOA THERE !!!! The TDC can be determined by pulling a precombustion chamber...
like hundreds of dollars and hours of labor difference!!!!!
I think hes referring to the 2mm lift method.

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  #62  
Old 07-22-2011, 02:40 PM
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Quote:
Originally Posted by Army View Post
...Nice the method in the FSM is similar. However, the FSM method is more accurate as it uses the design of the head with its vertical valve stems and a DTI to do this for us....
You would be using a DTI through the hole left by the precombustion chamber to get vertical placement ALSO.....and the difference in labor is significant...
But you can not use the top measurement alone and be accurate ... you must use equal points of the piston in the bore and take the middle between them to get TDC....
AND as YOU mentioned... there it that possibility of dropping a valve into the bore.... using that method...

I have raised enough red flags and stated my physics argument to the best of my ability... so that anyone reading this should understand they need to research it...

Last edited by leathermang; 07-22-2011 at 02:55 PM.
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  #63  
Old 07-22-2011, 02:46 PM
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Hey Army, pulling the springs on a set of valve to find TDC has less risk than pulling a pre chamber IMO. I don't know why that leather guy loves to pull the pre chamber so much. Can't believe he advises people to pull the pre chambers for routine inspection. Pre chambers are not cheap and the chance of something going wrong is high in pulling them.

Quote:
Originally Posted by Army View Post
Well I see what you are saying - that would be pretty incompetent. You wouldn't have to remove the head to check though:-

Set the engine with the markings to TDC for number one cylinder. Remove the front group of rocker arms and remove the valve nuts and valve spring on one of the valves on #1 cylinder. Carefully lower the valve onto the top of the piston crown.

If the piston is indeed at TDC the valve will drop by a few millimeters say 6mm.

If the valve stem starts to disappear - quickly pull it back up before it drops into the cylinder... otherwise will need to remove the head to retrieve the valve.

FYI - this is part of the procedure in the FSM for setting up the position of the tachometer sensor on the front of the engine.
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  #64  
Old 07-22-2011, 02:52 PM
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Quote:
Originally Posted by leathermang View Post
You would be using a DTI through the hole left by the precombustion chamber to get vertical placement ALSO.....and the difference in labor is significant...\..
The pre-chanber is at an angle relative to the piston top. the valve stem is vertical in relation to the piston top. It is much easier to set up a dial indicator on the valve stem than in a pre chamber. Ther labor difference is significant in favor of the valve stem method.
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  #65  
Old 07-22-2011, 02:55 PM
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Army, Funola has shown before that he has no concept of how vital to the efficient use of fuel in our engines the cleanliness of the tiny radial holes... different sizes even.... are ... along with the importance of the pintle to atomize the particles so they can be sent out through those holes... at several HUNDRED THOUSAND miles on most of our engines... checking to see that they are clean and working properly is not even sorta hard to justify...
There are several reports in the archives of the pintle having been burned and in pieces at the bottom of the precombustion chamber... thus not only not doing ITS job.. but covering some of those fuel holes.
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  #66  
Old 07-22-2011, 02:59 PM
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Originally Posted by funola View Post
The pre-chanber is at an angle relative to the piston top. the valve stem is vertical in relation to the piston top. It is much easier to set up a dial indicator on the valve stem than in a pre chamber. Ther labor difference is significant in favor of the valve stem method.
You have missed the concept... you are only needing to determine the same point of piston travel in the bore before and after having passed TDC....
But I am not sure that a vertical shot at the top of the piston is not available from the top of the head... even though the PCC is at an angle...
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  #67  
Old 07-22-2011, 03:00 PM
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Quote:
Originally Posted by funola View Post
The pre-chanber is at an angle relative to the piston top. the valve stem is vertical in relation to the piston top. It is much easier to set up a dial indicator on the valve stem than in a pre chamber. Ther labor difference is significant in favor of the valve stem method.
Good point about the pre-chamber funola being at an angle it wouldn't be the best position to measure piston height in my opinion. A DTI is best used at 90 degrees to the surface being measured - it is still a tight fit on top of the valve stem though if you've got a stubby probe like on my DTI...
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  #68  
Old 07-22-2011, 03:07 PM
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OK we've had our fun - what about the OP's problem

Here's my advice Sethza - look through the information and see if you can find a way that suits you to determine if TDC on #1 cylinder coincides with the timing marks or not.

I'd then go for the 2mm lift method to check chain elongation - this is one thing we can all agree on (I think!) then you'll know for sure whether the engine is set up correctly or not.
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Last edited by Stretch; 07-22-2011 at 03:09 PM. Reason: I spelt the OP's name wrong...
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  #69  
Old 07-22-2011, 03:08 PM
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You don't need a DTI AT ALL...
as the guy in the reference I gave showed... he just used a method to stop the piston....and then came from the other side.... split the difference....so this ' vertical ' need is just in yall's heads...
It is just to find equal distance points in the bore from TDC...
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  #70  
Old 07-22-2011, 03:12 PM
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Quote:
Originally Posted by leathermang View Post
Army, Funola has shown before that he has no concept of how vital to the efficient use of fuel in our engines the cleanliness of the tiny radial holes... different sizes even.... are ... along with the importance of the pintle to atomize the particles so they can be sent out through those holes... at several HUNDRED THOUSAND miles on most of our engines... checking to see that they are clean and working properly is not even sorta hard to justify...
There are several reports in the archives of the pintle having been burned and in pieces at the bottom of the precombustion chamber... thus not only not doing ITS job.. but covering some of those fuel holes.
Huh??? Pintle burned and in pieces in the PC covering fuel holes? The pintle in on the injector nozzle. If they are burned and fallen off (highly unlikely) the engine will run like crap and you pull the injector to see what's wrong, not the pre-chamber.
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  #71  
Old 07-22-2011, 03:13 PM
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Quote:
Originally Posted by leathermang View Post
You don't need a DTI AT ALL...
as the guy in the reference I gave showed... he just used a method to stop the piston....and then came from the other side.... split the difference....so this ' vertical ' need is just in yall's heads...
It is just to find equal distance points in the bore from TDC...
I get it - I get it - I do - honest.

But you're saying a two point measurement and a bit of calculation is better than an almost continuous multi point measurement.

I disagree.

Sorry.

Like I said before we'll have to agree to disagree on this one.
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  #72  
Old 07-22-2011, 04:38 PM
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Seems to me that you ought to be able to confirm TDC versus BDC just by looking at the cam lobes. You don't need a dial indicator to see a 90 degree difference in lobe positioning.

Confirming TDC versus BDC is probably easier to do at TDC between the exhaust and intake strokes. Exhaust lobe should be phasing out and intake lobe phasing in.

Last edited by tangofox007; 07-22-2011 at 05:06 PM.
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  #73  
Old 07-22-2011, 05:14 PM
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Quote:
Originally Posted by funola View Post
Huh??? Pintle burned and in pieces in the PC covering fuel holes? The pintle in on the injector nozzle. If they are burned and fallen off (highly unlikely) the engine will run like crap and you pull the injector to see what's wrong, not the pre-chamber.
GOTCHA !!!
You don't even know that there is a pintle in the precombustion chamber that can burn ....

No wonder you do not understand the need to inspect it in certain kinds of complaint diagnosis....

For others with more open minds.... the pintle is under the injector and connected to the sides of the precombustion chamber...
its function is to help break up the stream of fuel and direct it towards the small radially drilled holes in the bottom of the precombustion chamber...
they can not be inspected in place because
1. the pintle is in the way and
2. they are pointing out in various directions from the middle of the bottom of the precombustion chamber... so removal is the only way to inspect and clean.

Funola , you made my day with that admission ... I had wondered why you have attacked my suggestions on the PCC's...
I suspect you do not own a paper copy of the FSM.. is that correct ? if you do .. the picture is on page 01.8-417/2 F2.
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  #74  
Old 07-22-2011, 05:35 PM
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Just a Guess !!!!

Quote:
Originally Posted by Army View Post
I get it - I get it - I do - honest.
But you're saying a two point measurement and a bit of calculation is better than an almost continuous multi point measurement.
I disagree.
Sorry.
Like I said before we'll have to agree to disagree on this one.
http://www.thedirtforum.com/degree.htm

"" Attach degree wheel to crankshaft and install pointer. Adjust pointer to approximate TDC on the wheel with piston at top of cylinder.

1. Install indicator to contact the piston near the center to minimize the effect of piston rock at TDC. Rotate crank through TDC in normal direction and 0 indicator at the highest reading. Continue to rotate crank in normal direction of rotation and record the degree wheel reading at .100 indicator reading before TDC. Continue rotating until you are at .100 after TDC. Record your degree wheel reading. TDC will be half way between these readings. You can use a point other than .100 as long as it’s the same point on each side of TDC. Adjust your pointer to read 0 at this point. Top Dead Center is now accurately known. This is a very important step because there is a point a few degrees before and after TDC when the piston moves very little. This method measures the same point on each side of TDC where piston movement is much greater per degree of crank rotation than at TDC. A positive stop such as a strap with a bolt to hit the piston can be used. The crank is rotated until the piston hits the stop and degree wheel reading is recorded. Rotate the crank in the opposite direction until the piston hits the stop and record the reading. Halfway between the readings is true TDC. If the heads are on the engine a stop can be screwed into the spark plug hole to contact the piston. Be sure to remove the rocker arms on that cylinder or you risk bending a valve if it hits the stop when open. Either method is accurate ""

http://www.totallytriumph.net/TriumphCarForums/viewtopic.php?f=3&t=58

"TDC, Top Dead Centre, is an essential reference point of engine tuning. On a fully assembled engine, there are markings on the crank pulley and a pointer on the timing cover, but during an engine rebuild you can't use those, and that pointer can be moved or bent. So how to find or check TDC?

The usually described method is to use a Dial Gauge Indicator, a piece of precision engineering kit. It translates very small movements into the rotation of a needle on a dial, and allows very small movements to be easily seen and measured. But when setting TDC the movement is very, very small. In fact it's no movement at all! The piston slows down and stops as it reaches the top of its stroke, and then reverses direction. At TDC, even a dial gauge will find a significant range of crankshaft rotation in which it doesn’t move, and TDC could be anywhere in that range. This way of finding TDC is not that accurate; here’s a better way!"""

http://www.vwdiesel.net/forum/index.php?action=printpage;topic=21950.0

.""..the reason being that the at both TDC and BDC the crank can actually move quite a few degrees with no perceptible piston movement.

The gold standard is to index piston (or in this example, skirt) movement some amount *before* it bottoms out, from both sides of the crank's rotation. TDC / BDC is then exactly in the middle.""

http://www.practicalmachinist.com/vb/general-archive/ot-how-find-tdc-gas-engine-153336/

""Attach a degree wheel to the crankshaft, and set a dial indicator such that its stem can extend thru a spark plug hole to contact the piston.

Rotate the engine forward by hand until the indicator passes thru TDC and shows the piston moving downward by some set amount, say .030". Make a note of the reading on the degree wheel when you reach .030 on the indicator.

Now rotate it backward until it passes thru TDC and down to .030 in the opposite direction, and record thhe degree wheel position at this point.

TDC is halfway between the two readings you recorded from the degree wheel.

Because of the amount of angular movement of the crank when the piston is near TDC but the piston movement itself is near imperceptible, any other method is just a guess.""
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  #75  
Old 07-22-2011, 05:49 PM
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Quote:
Originally Posted by tangofox007 View Post
Seems to me that you ought to be able to confirm TDC versus BDC just by looking at the cam lobes. You don't need a dial indicator to see a 90 degree difference in lobe positioning.

Confirming TDC versus BDC is probably easier to do at TDC between the exhaust and intake strokes. Exhaust lobe should be phasing out and intake lobe phasing in.
Oh right duh forgot about that.

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