View Full Version : Scratch in cylinder


silver68
01-16-2010, 08:35:31 AM
My engine refresh just keeps getting more aggrevating and more expensive. I just wanted to freshen up my shortblock to put on my dart heads and new intake. Had the block cleaned, new freeze plugs cam bearings and a ball hone.. Looking at at cylinder wall on number one hole and have a scratch still going up about 3/4 of the way up and next cylinder one not as bad going up about half. Its enough to cath a nail on. No ridge on top of cylinder so I thought I would be Ok with just a garage rebuild. Now Im thinking if I should go up to the next overbore size wich would be 40 over. Will the new iron rings seat with these scratches or am I going to have oil smoker.

a550550
01-16-2010, 09:40:33 AM
if you can catch it with your fingernail, it needs to come out. You need to check cylinder size and taper. If the clearance is too much now, it will need a bore.

You can check that by putting the ring in, and measure end gap. Use the piston to push the ring in level at different areas of the cylinder, measure the end gap, and compare it to the sheet that comes with the rings. Getting the scratch out will do no good if the cylinder taper is over spec already.

pdq67
01-16-2010, 10:23:40 AM
Imho, ball-hone it and go!

pdq67

markw
01-16-2010, 11:11:34 AM
Imho, ball-hone it and go!

pdq67 X2 Think of the area of the scratch ( width x depth). It will fill in with carbon and disappear. Don't worry about it.

silver68
01-16-2010, 04:11:32 PM
put in a new hasting ring and measured gap
top .022
mid .021
bottom .020

piston to wall gap .006 (top of bore)

Could I get away with trying to ball hone out the scratch and try to even out cylinder taper.

http://i817.photobucket.com/albums/zz99/spdfrk99/101_3903.jpg

markw
01-16-2010, 08:21:46 PM
Ball hone is a surface conditioner only. It won't remove enough material to measure. Any idea what made the scratches? Are the pistons OK?

silver68
01-16-2010, 08:32:34 PM
bought this shortblock used. Looked like the cam gear made contact on the block and got metal in the oil. Had some scoring on the crank, had to go 10 under on it. Engine ran good, just took it to the strip, but just wanted to freshen it and found this.
Pistons look ok without alot of wear, just cheap cast flat tops so no big deal to replace if I have to overbore.

z28rod
01-16-2010, 08:37:26 PM
i would just give it a hone and new moly rings and run the crap outta her..

silver68
01-17-2010, 06:28:23 PM
put a hone on the cylinders that were scratched, actually noticed a couple more. Im going to put it together and see what happens.

CNC BLOCKS
01-17-2010, 06:57:33 PM
i would just give it a hone and new chrome moly rings and run the crap outta her..


No such thing as chrome moly rings

z28rod
01-17-2010, 07:39:41 PM
ok moly rings ha i stand corrected, it was late dude and iam over 50 and its cold and i have shrinkage..........

silver68
01-17-2010, 08:32:53 PM
I hate shrinkage! Would cast rings work, I have a new set and my ball hone is for them 230 grit

Damon
01-17-2010, 10:27:09 PM
You mean just plain cast iron $20 set of rings? I wouldn't (although I have). Ductile iron with a moly face has been my go-to choice for years now. They just seat so nice and so quick compared to old cast iron rings.

Plus you don't have to be biting your nails down to the nub worrying about breaking one during install.

I'm not saying you gotta drop $200 on a set of rings, but you don't have to go bottom-basement either.

That picture, above...... those are your scratches? Nothing to worry about. I've run a lot worse than that. In fact, a few summers ago I helped my neighbor rebuild the engine on his old Ford tractor. Cylinder head cracked and actually lost chunks into the cylinder. One of the cylinders had a nasty groove worn up and down it from the carnage. Not just a scratch- a groove you could lose your fingernail inside of. I advised him against just doing a quick hone and ring job. He said it would be fine and proceeded forward. End result....... well....... um........ I was wrong. It worked just fine. Still runs just fine today. No smoke, no significant loss of compression (maybe 5 PSI).

77wolf10.85
01-18-2010, 12:25:40 AM
Feel the bottom of the bore to see if it is sharp, it may need chamfered a little. Thats what causes the scratches down lower in the bore. The sharp edge acts like a scraper and removes the oil film from the piston skirt, result is scratches at the bottom of the bore.

I just take a dremel to them, and you don't have to do a full 360, just where the skirt runs out the bottom of the hole.

Where did the cam gear get into the block? On the main oil gallery boss?

silver68
01-18-2010, 08:12:54 PM
heres where it make contact. It was like that when I took out the old summit cam and put in the crane. The back of my gear looked good when romoved. I bought a cam button and the thrust bearing kit to hopefully prevent this next time. I am going to check the bottom of the cylinders and smooth out if necessary

http://i817.photobucket.com/albums/zz99/spdfrk99/101_3907.jpg

pdq67
01-18-2010, 10:08:54 PM
I knew a pair of Brothers that bought an old 600 cfm portable A/C w/ an old flathead straight 6-banger Hercules or a Waukesha that all they did was install the lower end bearings, rings and grind the "cracked" valves and did a seat grind and the old SOB ran fine.

They used it to sandblast house trailer's down to bare metal so they could repaint them and then flip them to make a buck until the city got on them b/c of the dust and noise. Pre-EPA days here!!

pdq67

Ps., I saw the regound valve faces before installation and never said a word...............

77wolf10.85
01-19-2010, 09:54:00 PM
heres where it make contact. It was like that when I took out the old summit cam and put in the crane. The back of my gear looked good when romoved. I bought a cam button and the thrust bearing kit to hopefully prevent this next time. I am going to check the bottom of the cylinders and smooth out if necessary

http://i817.photobucket.com/albums/zz99/spdfrk99/101_3907.jpg

yup, main oil gallery boss

If you're running a FT cam the button is a waste of effort. Won't hurt anything but it definitely won't prevent your deal. The back side of the gear has a thrust face that runs against a thrust face on the block right around the front of the #1 cam bearing(bottom of your pic). Limiting forward travel with a button does nothing to the rear side.......

An aftermarket gear is what did that.

You need to grind it down some, then check it against the new gear.

ok, 2nd reread saw thrust brg kit. nevermind.

BigBlock73
01-20-2010, 07:03:21 AM
To me,it looks like someone "dimpled" the block around the plugs,with a chisel, to keep them from backing out.
Marks are to symmetrical

z28rod
01-20-2010, 07:06:34 AM
To me,it looks like someone "dimpled" the block around the plugs,with a chisel, to keep them from backing out.
Marks are to symmetricalthats normal, its the groves above the middle plug that they are talking about.