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1293 Pistons And Cr


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#31 Moke Spider

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Posted 10 March 2019 - 05:03 PM

 

Ok so I have posted this info on my other thread 1275 Rebore.

 

4ojoLRS.jpg

 

Using the DTI Gauge I found TDC and then set the gauge on the block face and zero'd it. Then gently releasing the magnet I span it around over the piston crown and re-engaged the magnet. Doing this a few times and on 3 of the 4 pistons I found the piston to deck height to be 15 - 15.5 thou. 

 

 

This in not an accurate method to measure TDC.

 

If you are going to use a dial gauge, then mount it so the plunger is over the gudgeon pin, not off to the side of it like this ^. With the normal piston to bore clearance and the rock you'll have on a cold piston, that could be anything up to 0.010" off.

 

Also, if using a dial gauge, always measure with the piston rising, not falling.

 

A more accurate method again is to use a Piston Stop.



#32 JonnyAlpha

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Posted 10 March 2019 - 05:42 PM

 

 

Ok so I have posted this info on my other thread 1275 Rebore.

 

4ojoLRS.jpg

 

Using the DTI Gauge I found TDC and then set the gauge on the block face and zero'd it. Then gently releasing the magnet I span it around over the piston crown and re-engaged the magnet. Doing this a few times and on 3 of the 4 pistons I found the piston to deck height to be 15 - 15.5 thou. 

 

 

This in not an accurate method to measure TDC.

 

If you are going to use a dial gauge, then mount it so the plunger is over the gudgeon pin, not off to the side of it like this ^. With the normal piston to bore clearance and the rock you'll have on a cold piston, that could be anything up to 0.010" off.

 

Also, if using a dial gauge, always measure with the piston rising, not falling.

 

A more accurate method again is to use a Piston Stop.

 

 

So when checking TDC always do it on the rise (I believe I did) but I'll make sure I measure at the centre of the piston.

 

The picture above though was measuring the piston crown to deck height.



#33 Moke Spider

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Posted 10 March 2019 - 05:59 PM


The picture above though was measuring the piston crown to deck height.

 

 

OK, but the same applies and for the same reason.

 

At a pre-machined stage, Cooperman's method would be a good guide to this, but I'd suggest running an Oil Stone over the deck for about 10 minutes first,






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