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RIP (12/27/60-7/18/15)
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767 Posts
Discussion Starter #1
I just can't get a piston installed in my 400 HO block.
I know I have the correct rings.
the notch faces forward.
The piston is on the side of the block that's it's supposed to be.
Good tight fit on my ring compressor.
But every single time they hang up on the lower oil ring.
And yes they all move easily side to side on the pistons,
the oil baffle colors line up and do not overlap
WTF??????????????
:shutme:willy::shutme:willy::shutme
 

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336 Posts
Use a lot of engine oil on the piston skirts and rings and inside of the compression tool.

Get it lined up and start tapping the top of the piston with a wooden handle of a very large hammer. Tap it until the oil scrapper is about 1/4" from entering the bore. At this point give it a huge hit with the wooden handle of the large hammer. You want to get the ring pack in on one hit.
 

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64-67 Expert
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8,569 Posts
Did you set the end-gap on the rings? Make sure the gaps are correct, and clock the rings as per instructions with the ring mfgr. I use a coffee can with motor oil in it to dunk the piston. Go easy....you should NOT have to force anything. You do NOT want to break a ring here......
 

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RIP (12/27/60-7/18/15)
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767 Posts
Discussion Starter #4
Got two of them in!!!
amazing what a slattering of oil does.
Rings are clocked good too yay!!!
 

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once you get one, it goes easy after that, lotta patients, good amount of oil and a good quick rap at the right time
 

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New pistons or old ?? carbon can build up in the grooves preventing complete ring compression. As already said double check end gap, you shouldn't have to really pound them in, firm tapping should do it.
 

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+1 to what geetee said, protect the crank journals. I found out the hard way many years ago what happens if you don't.
 

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RIP (12/27/60-7/18/15)
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767 Posts
Discussion Starter #9
They are 20 over and new.
Got them all in and torqued down
Been a while!
Whats that slight depression on the tops of the bores?
seems odd.
thanks for all the help
 

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Former Super Moderator
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9,919 Posts
It helps with the flame path.
I`ve seen shards of aluminum from manufacturing stuck in the ring groves as well which will make the new rings hang up when installing.
If you have any pistons that did not get oiled on the way in, I'd pull them back out and oil them. I use a can just big enough to fit the piston in and then dip the whole top of the piston to past the wrist pin.
 

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5,751 Posts
Whats that slight depression on the tops of the bores?
If you're talking about those slight chamfers in the block near the top of the bore, at about the 11 o'clock and 2 o'clock positions, those provide some additional clearance for the valves to help "un-shroud" them for improved flow. If you sit a head on top of the block and then look up from underneath through the cylinder bore you'll see that the outside edges of the valves are -very- close to the cylinder walls.

Bear
 
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