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  #46 (permalink)  
Old 12-13-2012, 05:42 PM
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Quote:
Originally Posted by maxdudy View Post
...crank was stated as a 10-10 under.
He gave me bearings for a 10-10 crank, and I did not check.
After assembeling 3 Main caps (Torque could not spin crank. Checked and hasd 20-20 crank.
I think you have that backwards. 10 under bearings on a 20 under main journal would spin just fine, except for the extra 10 oil clearance. Now 20 under bearings on a 10 under crank...

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  #47 (permalink)  
Old 12-14-2012, 05:22 AM
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Quote:
Originally Posted by painted jester View Post
"What do you mean by piston to bore clearence. Is that the gap inbetween the two."
YES

Aluminum expands about 1.7 times the rate of cast iron so there has to be room for that expansion. Rather then me typing this I'll just add this attachment! Remember: Different manufacturers and piston types(forged, cast,ETC,ETC, have different recommended clearances ) dont just open a repair manual and think that's correct!!!! you should always have the pistons before the block gets bored..That way the machine shop can do the final hone to get the exact piston clearance you need.. Most pistons you measure the skirts with a micrometer 90deg from the pin, just below the oil rings.

Measure the cylinder bore and subtract to get the clearance.

The piston is larger at the bottom of the skirt and smaller at the compression rings to allow for expansion of the piston dome. Pistons are also "cam-ground" (egg shaped, not perfectly round) as well so measuring somewhere other than the piston mfgr's. recommendations will give you an inaccurate number.


Jester


This is one way to check!
http://www.rosspistons.com/informati...stallation.pdf
Cam ground means the piston is larger diameter measured perpendicular to the pin or the thrust diameter, than it is measured in line with the pin. That is because the piston expands faster in line with the pin due to the extra amount of aluminum in the pin bosses. The piston to cylinder wall clearance is the difference between the bore size and the diameter of the piston measured across the thrust diameter, just below the oil ring.

Clearances for forged aluminum pistons:
SAE 4032 aluminum ...high performance street, .002" - .0035"
SAE 2618 aluminum... competition, boosted, scuffs easily, .004" - .0065"

If your engine has 400 - 450 HP, driven on the street and want durability, use pistons that are made of SAE 4032 aluminum. Engine with more than 450 HP should use pistons made of SAE 2618 aluminum. SAE 2618 aluminum is low silicon and is softer and need to checked for wear, scuffing and are replaced more often.
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  #48 (permalink)  
Old 12-14-2012, 02:52 PM
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Quote:
Originally Posted by MouseFink View Post
Cam ground means the piston is larger diameter measured perpendicular to the pin or the thrust diameter, than it is measured in line with the pin. That is because the piston expands faster in line with the pin due to the extra amount of aluminum in the pin bosses. The piston to cylinder wall clearance is the difference between the bore size and the diameter of the piston measured across the thrust diameter, just below the oil ring.

Clearances for forged aluminum pistons:
SAE 4032 aluminum ...high performance street, .002" - .0035"
SAE 2618 aluminum... competition, boosted, scuffs easily, .004" - .0065"




If your engine has 400 - 450 HP, driven on the street and want durability, use pistons that are made of SAE 4032 aluminum. Engine with more than 450 HP should use pistons made of SAE 2618 aluminum. SAE 2618 aluminum is low silicon and is softer and need to checked for wear, scuffing and are replaced more often.
Are you correcting me or just adding additional info I didn't cover?


JUST REMEMBER TO GO BY THE PISTON MANUFACTURES SPECS (they may differ Quite a bit)!!!
http://www.jepistons.com/PDFs/TechCo...instrc4032.pdf

I'll add a little more

"Cam ground piston Definition from Science & Technology Dictionaries & Glossaries
Engineering Dictionaries
Dictionary of Automotive Terms
cam-ground piston: .
A piston with a skirt that is ground slightly egg-shaped or oval-shaped. The widest diameter of the skirt is at right angles to the piston-pin axis. When it is heated, it becomes round. The design allows for a closer fit in the cylinder so that there is a reduction of blowby gas, cylinder scuffing, and piston slap ."




Measuring the piston
Fig 7.7
Using a micrometer, measure the piston skirt across the thrust faces as shown in Figure 7.7. In most cases, the measurement is taken at a point which is approximately one-third of the skirt height. This is the nominal diameter of the piston and should be the greatest dimension.
Other measurements can be taken as a check and to make sure that the piston has not collapsed. A collapsed piston will have a reduced diameter at the lower end of the skirt.
Fig 7.8
The engine manufacturer’s service manual should be consulted for piston dimensions and clearances. It will also have information on how to measure the piston. Some pistons are cam-ground, some have a tapered skirt and some are slightly barrel-shaped. All pistons are not measured in the same way.
Figure 7.8 is an example of piston measurement. It shows the places on a piston where measurements would be taken. These are as follows:
http://www.hotrodders.com/forum/atta...1&d=1355522014


BB is the nominal piston diameter
AA is the reduced diameter after cam grinding
CC is the diameter at the top of the skirt
DD is the diameter at the bottom of the skirt
EE is the reduced diameter at the lands.
The pics posted bellow Sorry



All modern cam-ground pistons, measured for clearance 90 degrees (right angled) to the wrist pin. and measured for clearance this way.
Thus, if the block is bored exactly .030" oversize, the clearance will be what the manufacturer intended, usually around .004" to .005" at a point perpendicular to the wrist pin.

LOLhttp://www.hotrodders.com/forum/attachment.php?attachmentid=69805&stc=1&d=13555222 68

Man!!! I sent this early I hit the send again instead of the preview

LOLhttp://www.hotrodders.com/forum/attachment.php?attachmentid=69805&stc=1&d=13555222 http://www.hotrodders.com/forum/attachment.php?attachmentid=69809&stc=1&d=13555235 4268
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Last edited by painted jester; 12-14-2012 at 03:20 PM.
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  #49 (permalink)  
Old 12-15-2012, 01:54 AM
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bearings

Your bearings are worn out. Make sure that the wear is even all across the surface. If it is not, then you should line bore/hone the block and straighten the crank. Don't do this yourself. Crank straightening is an art. Mike the crank to be sure it is still round, then buy new bearings to provide the proper clearance. The more clearance you run, the lower your oil pressure will be. I like to see oil pressure in my V-8 Vega (350 four bolt main early LT-1), so I use .001" on the rods and .0015" on the mains. It carries 40 psi at hot idle on a 100 degree day with the air on full blast. It also revs to 8,000 rpm. My 327 small journal ran for 300,000 miles and still didn't get down to the copper. I give the credit to Valvoline 40w Racing oil and STP. The STP stays on the bearing surface when you shut the engine off, while the hot oil drips back into the pan. The next time you start up, the STP gives some lubrication until the oil pump can start delivering oil again. I also suggest a magnetic drain plug so that you can check to see if you are having undue engine wear. After break-in, your engine should not have ANY hair (metal particles) on the drain plug. if it does, then your oil is not doing its job. I recommend NOT using Pennsylvania based oils because they have a high ash content and cause excess wear. Paraffin based oils are much better (Valvoline, Havoline, etc.). Valvoline 40w Racing oil is the Army's first choice for their aircraft piston engines. They also suggest the STP "if you can find it". Stay away from anything purple.
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Old 12-15-2012, 07:09 AM
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There IS going to be some metal worn off during the process of ring and cam break in. Fot that reason I believe seeing a film of magnetic particles as well as a metallic hue to the oil after the cam break in of a flat tappet engine the norm.

As for the rest of it, if that's your experience then so be it. But it is not going to be something that everyone- including myself- will agree to all of.
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Old 12-17-2012, 12:34 PM
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Quote:
Originally Posted by cobalt327 View Post
There IS going to be some metal worn off during the process of ring and cam break in. Fot that reason I believe seeing a film of magnetic particles as well as a metallic hue to the oil after the cam break in of a flat tappet engine the norm.

As for the rest of it, if that's your experience then so be it. But it is not going to be something that everyone- including myself- will agree to all of.
!!!!! Hit it on the button again


Jester
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Old 12-17-2012, 07:56 PM
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Thanks for the input

Last edited by ChevroletSS; 12-17-2012 at 08:10 PM.
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Old 12-17-2012, 07:59 PM
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Thanks Guys

Last edited by ChevroletSS; 12-17-2012 at 08:10 PM.
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Old 12-19-2012, 11:13 AM
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Your welcome

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Old 12-19-2012, 11:29 AM
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What kind of oil do u recomend for break in and what kind after break in? I dont want to use newer oils even if I have to order my oil online. Every oil I use looks burnt after a few 100 miles and always smells burnt. I want to use thicker oil than recomended for my truck which is 10w30. I want good added protection in a oil I use.

This is off subject but what is a ball park price on line honeing a 350
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