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#1
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What are these marks on cylinder walls
What is causing these vertical marks on the cylinder walls. I can see them, but I can`t feel them. Motor is a 340.
As always, Thanks |
#2
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Can't tell from the pic if that's the thrust side or not, but it's the rings scuffing the walls up. I would guess that they are broke, or the gap is too tight and they are butting ends together. Time to pull it down, that's for sure.
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#3
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as dwc said... broken rings, or possibly the skirt of the piston scuffung the cylinder walls.
if there is no excessive wear, you can probably get by with a quick hone job and a new set of rings. just make SURE that everything is CLEAN before you assemble things, and use plenty of assembly lube!
__________________
Where are we going?... And why am I in this hand-basket? 84 D250/440/3.54:1 dana 60/16" wheels, 31" tires/A-727trans/3" header mufflers/weighs 5000 lbs/13.22 sec @ 103+ mph. |
#4
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looks like the thrust side to me....
have them mic the bores, if they are too worn out your pistons will rock in there and cause this. But Im guessing a hone job and rings will get you buy just fine. |
#5
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Looks like the pistons have galled from lack of oil or overheating to me.
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#6
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I think the pistons are too tight in the bores. Pistons will have worn pretty bad too.
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#7
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Don't have a picture but in about the same position there is a small divot in the wall of one cylinder in my 360. It's less than a 1/16" in diameter and maybe 0.020" deep. It's like something got into the cylinder and was jammed between the piston and the wall. The cylinders are otherwise straight and all measure between 4.001" and 4.002".
Any reason to be concerned? Safe just to hone the walls and re-ring the engine? |
#8
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The scuffing is consistent in all cylinders. I thought it may be the rings, but then when I saw the consistency of the scuffing in all cylinders I thought I might rule that out. I think maybe the crankshaft end play could have contributed. I checked it to be .031 which is too much.
Right now I`m seriously considering replacing it with a 360/380 crate motor. Any thoughts? Considering what you get with a crate motor, $4000.00 seems reasonable. If I get into this 340, I might go wild and spend that much any way. L8R |
#9
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It looks like scuffing from the piston skirts to me. The excessive endplay could have contributed to it but I'd suspect some clearance issues, it doesn't look that bad though, but it's hard to tell from the picture.
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#10
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Looks to me like dirt in the oil.
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#11
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ok, my turn, looks like the rings were too tight, it got hot, or the pistons too tight.
another possibility is carbon burn, that is where the rings leak compression and burn the oil in the cylinder wall, the sighns for this is that the damage is not to the top of the wall, an dnot all the way down (like normal scarring) carbon burn can get bad quik, so hone it and throw her togrther, make sure you use high quality oil, and proper break in. also make sure you check the gaps. what kind of piston are they?i have this friend who orderd a crate 380hp, he took all winter puting it in, and the crank siezed up after 1500 mi, i have heard horror story's, so id keep yer old one |
#12
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Not sure about the markings on the walls, but if you can't feel anything I wouldn't do much more than clean up the bore and re-ring if its within tolerances. Re: crate motor, I gave that a ton of thought and wound up having my 360 done properly by a local and reputable race engine builder, stuck in a Mopar cam and lifter , some 9:1 cast pistons, and saved about $1500 plus I know who built it and got a warranty. I'd be tempted to take that route if you have a reputable shop in your area, just ask around your local tracks and speed shops.
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#13
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Piston Scuff
Looks like the engine was run too cold. The pistons are oval when they are cold. They expand to a round configuration at proper operating temp. If they are overheated the scuff marks will be at the front and rear of the cylinder. Over cooling causes a scuff where yours is scuffed because the piston does not expand enough and get round when it is run cold. If the rings were too tight, they would scuff all the way up to the ridge line. Broken rings leave a definite scratch in the cylinder. Dan
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#14
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Measure the pistons at the skirts to check for any collapse before reusing the slugs.
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#15
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How much running time on the engine? Why did you pull the engine apart? What kind of problem(s) did you have? Does this area of the bore look highly polished like a mirror or dull?
Mitch |
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