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Discussion Starter #1
I was having some serious smoke/steam comming out of my catch can on my 351 turbo.So i did a compression test.Came up with 130ish PSI on all cylinders except 1 it read 35psi.This was on the driverside only since i didnt wanna take the down pipe off.So i looked at that plug on the cylinder that read 35 and it was black,the rest was goldenish brownish.Well got the engine pulled and BOTH the head gaslets are fine,but the on cylinder that tested low the valves are black the rest are normal,and the piston and cylinder wall looks fine on every cylinder.I cranked the motor over by hand and they all moved freely.When i was taking off the lower intake only 2 bolts were tourqed,the rest came out by hand.Could this be the cause of the low reading in 1 cylinder,or the reason for all the steam????I havent taken off the oil pan yet but will tomorrow.Also the oil looked perfect and so did the coolant.Dudes i'm lost at this :shrug:Any help would be great!!!!
 

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The intake should not affect the compression. Too bad you didn't do a leakdown, you could identify the area where the leak is.
Maybe you have some broken ringlands or leaking valve.
Erich
 

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Discussion Starter #3
I dont have a compresser to do so else i would of done a leak down!Is there a way to check the valves if they leak with the heads off?If the ring lands or rings are messed up wouldnt it score the cylinder walls????
 

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Flip the heads over and set them on a bench, make them level. With spark plugs in, pour a liquid in the chamber to the very top. I use parts washer solvent. If the liquid runs out past the valve, you have problems.
When you said "steam/smoke coming out of catch can" , were you refeering to the crankcase catch can? If so, I would lean toward a ring issue. We call that blow-by!!
Yes, the rings can be damaged and it can be very hard to tell from the top.
 

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Discussion Starter #5
Flip the heads over and set them on a bench, make them level. With spark plugs in, pour a liquid in the chamber to the very top. I use parts washer solvent. If the liquid runs out past the valve, you have problems.
When you said "steam/smoke coming out of catch can" , were you refeering to the crankcase catch can? If so, I would lean toward a ring issue. We call that blow-by!!
Yes, the rings can be damaged and it can be very hard to tell from the top.
Yes i had hoses comming off the valve covers into a can,so yes it was a catch can for the blow by or PCV system
 

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Yes i had hoses comming off the valve covers into a can,so yes it was a catch can for the blow by or PCV system
Check the heads, but I would guess your problem is the rings.
Take a close look at the pistons again. Look for any melting around the edges, just above the ring land.
 

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Discussion Starter #7
Check the heads, but I would guess your problem is the rings.
Take a close look at the pistons again. Look for any melting around the edges, just above the ring land.
Ok yes sir,doing it tomorrow!
 

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Discussion Starter #8
I figured out i think i have a slightly cracked piston in that cylinder.



























So now i know i need a new piston based off these numbers from on the piston what are the part numbers?Here are a few pics of the numbers they are on the inside of the pistons




There is also a 12 on it and also a C on it,then on the tops they are stamped 40 so i assume 40 over?
 

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Oversize is stamped on the top. Usually the part number is stamped on top as well, Unless it is just a plain'ol cast piston. If you can spare a little cash,Now is the time to upgrade to forged pistons.
 

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Discussion Starter #10
Oversize is stamped on the top. Usually the part number is stamped on top as well, Unless it is just a plain'ol cast piston. If you can spare a little cash,Now is the time to upgrade to forged pistons.
Well i am looking into forged of course but i'm also thinking stroker also......they are just cast pistons...the rods are OEM with a part number.
 

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Well i am looking into forged of course but i'm also thinking stroker also......they are just cast pistons...the rods are OEM with a part number.
Cast pistons!!!!!!!!!!!

The lowest you should go is hyper. pistons. They can survive on 10 lbs of boost and less

anyway good luck
 

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Discussion Starter #12
Cast were in there when i bought the motor thats why they are in there and i ran them.I'm ordering all new rod and pistons,haveing it balanced and call it good also doing a stud girdle and main studs
 
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