Piston sideways????.. hope the world is not ending
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From: Marietta ga
Piston sideways????.. hope the world is not ending
OK durring an inspection of my short block, I fount that my number one piston is not square with the block. On the TOP Left, it is .009 inches out of the bore. On the BOTTOM Right, it is .009 inches in the bore..... My head porter says this is too far out. My motor is bored 40 over ad has been decked a couple of times, if that makes a difference. Could the machine shop have over bored it too much?? Does anyone have any suggestions, experience....ect....
P.S. I am going to get a mic on it tomorrow and get all the bore specs. I only had time to look at number one the other day
P.S. I am going to get a mic on it tomorrow and get all the bore specs. I only had time to look at number one the other day
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by Cory1970
OK durring an inspection of my short block, I fount that my number one piston is not square with the block. On the TOP Left, it is .009 inches out of the bore. On the BOTTOM Right, it is .009 inches in the bore..... My head porter says this is too far out. My motor is bored 40 over ad has been decked a couple of times, if that makes a difference. Could the machine shop have over bored it too much?? Does anyone have any suggestions, experience....ect....
P.S. I am going to get a mic on it tomorrow and get all the bore specs. I only had time to look at number one the other day
P.S. I am going to get a mic on it tomorrow and get all the bore specs. I only had time to look at number one the other day
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From: Marietta ga
How do I check height on the pin axis? I know I will get variations from rock, but should it even be rocking this much (.oo9)? Plus the variation is not vertically like I would assume. The variation is cocked sideways at about 10 o'clock and 4 o'clock, how could this be?????
The short block had about 3000 miles on it, and it ran great before I took off the heads. No piston rattle or anything...it might have had a very slight vibration, but it was not vary noticable. There was oil on the spark plugs, but my valve seals were blown out (shop put in cheap umbrella seals after I gave them the good ones). We assumed all the oil was coming from the valves because the seals and guides were so badly warn out.
The short block had about 3000 miles on it, and it ran great before I took off the heads. No piston rattle or anything...it might have had a very slight vibration, but it was not vary noticable. There was oil on the spark plugs, but my valve seals were blown out (shop put in cheap umbrella seals after I gave them the good ones). We assumed all the oil was coming from the valves because the seals and guides were so badly warn out.
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by Cory1970
How do I check height on the pin axis?
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From: Marietta ga
Originally Posted by Corvette Kid NC
Check the height only at either end of the pin, in other words at 3 or 9 o'clock. No other area will give you an accurate height measurement.
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From: Good health is merely the slowest possible rate at which one can die
St. Jude Donor '04-'05-'06-'07
Originally Posted by Cory1970
ok I see your point. I see why that would be best for checking deck heigth, but it is not the deck height I am so concerned with. I am concerned with the piston being highest at 10 and lowest at 4 o'clock. The pin axis should cause the highest point to be at 12 and lowest at 6 or vis versa. My deck height is close to zero at the pin axis, but why is there variation right and left. 9 and 2 o'clock should be at the same height but they are not.....
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Le Mans Master
Joined: Dec 2003
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From: Fremont CA
You said it is 0.009" above the deck? Even if you are talking about the "rock" of the piston, 0.009" (lets just round it up to 0.10") is pretty far above. I hope your machine shop used a BHJ "Block-Tru" fixture on the motor when they decked the block surfaces to true the deck surfaces to the cranckshaft centerline. The pistons should all be close to 0.010" above the deck if the block is properly machined. You will need to go to a think "MLS' type head gasket at least 0.050" thick to give yourself a proper clearance to the cylinder head. I would seriously conside a new machine shop if all the deck heigths are different or even more than a 0.005" variation.
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From: Who says "Nothing is impossible" ? I've been doing nothing for years.
Check to see if the rod is in the center of the piston on the pin, also check the sideplay on the rod big end on the crank, I forget the measurement but somewhere around .020" is max I think
Le Mans Master
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From: Watkinsville, GA and Glen Cove, NY
Cory, there is a great engine guy in Atlanta. His name is Gary Grimes and Grimes automotive. Not cheap but one of the best around. Sorry I don't have a phone number for you.
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From: Castro Valley Calif.
St. Jude Donor '03 thru '26
Originally Posted by MotorHead
Check to see if the rod is in the center of the piston on the pin, also check the sideplay on the rod big end on the crank, I forget the measurement but somewhere around .020" is max I think
This is a real good point. I don't know how much rock a forged piston has, but if you have a short compression height with a 4 thou clearance +/-, you'd get some rock/slap till it warmed up and tolerances tightened up. That should only be inboard and outboard though, not at the locations you mention. Are the rods bushed or pressed? Pressed rods that are off center might explain this kind of variance.....
