Need help with scored cylinders

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Freezerman

Freezerman

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Ok, I bought this 318 cheap because it had x heads on it. They look OK, but 2 cylinders have scoring. It has .030 over p4120281 pistons which I can't find out much about except they are 11.5:1.
How much scoring can be removed before new pistons are needed? What compression would these run with x heads?
 

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the other cylinder.
 

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Hone it and run hell out of it.
 
So you think pop out those two pistons and hone it, call it good enough? Are those pistons a good combo with x heads?
 
Light hone and re ring if anything, not to say it will remove scoring.

Yes, those pistons are designed for open chamber heads.
 
If that is a 11.5 (figured with a smaller combustion chambered 318 head) it may only be a 10.5 in reality! You need to cc the piston and head combustion. it may be a good street compression.

As far as the scares go. Hone and add fresh rings, if there is no real ridge at the top of the bore(aka cyl bore ware)

Did you here this eng run?
May want to pull the pan and see what the bearings look like.
 
Just make sure you have a good functioning PCV because you will have a little extra blow by - but I agree with the others. It's not a huge thing if you're looking for a budget deal.
 
If you're real worried about the scores, find a new block, 318's are cheep.
 
I am going to pull the pan and check the bottom end out also. You guys are talking about just clay ball hone right? I can't feel a top ridge at all. It came with 340 x heads. With those pistons and x heads what would be the compression aproximately?
 
I have not run this engine myself, but it has been run. I would like to know if this combination would run OK on pump gas. It has a Crane 272 in it. I am having a hard time finding out much info on this piston.
 
Freezerman

Those Pistons are TRW 'Forged' 11.5-1 Compression +.030" oversized.

A little tip, you can hone those Cylinders out, and pop in +.035" Rings.

A .007" Clearance {between the Piston-skirt and Cylinder-wall} is not uncommon for Forged TRW Pistons.

Note; The Brush Research {Flex-ball brush} may not take out the deeper scores in the Cylinder Wall.
 
Any ideas if those pistons with x heads will do OK with pump gas?
 
Those TRW Pistons are calculated for 11.5-1 Compression with the 318 Cylinder Heads {#2843675}.

That is also with a properly decked Engine Block.

With the 340 'X' Cylinder Heads {larger Combustion-chamber} you will lose about, .40 {4/10's} of
a Compression Point.
 
RustyRatRod said:
Hone it and run hell out of it.
Click to expand...

x3. I have done exactly that more than once over the years. People sweat these things but mostly they aren't a big deal at all.

If you could pull the heads off a bunch of good running engines, you would be surprised at how much of this kind of stuff you find.

The last 350 I built was running great but I wanted to pull it for a new cam, bearings and a basic look over. (74 GMC that had never been apart, my grandpa's old farm truck that he bought new and I inherited).

That old, good running truck had 7 broken rings.
 
Sealed Power Piston Rings

The cast iron or 'quick-seater' Piston Rings will work as well.

Softer material, seats quickly and will take up for any cylinder wall defects {ie; scratches and minor imperfections}.

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When you pull the pistons out, examine them closely to make sure you don't have any debris embedded in the piston skirts....If there is crap stuck in the piston, it will just scratch up the cylinder again.
 
Thanks again for the help. I will work on cc ing the head and pistons
 
it looks like someone dropped some crap in the cylinder changing plugs or running without an air filter
 
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