Jo, jag hade dom tankarna från början tills jag hittade följande på nätet från Captain Nortons mektips:
"Now, let me blow a few minds over honing:
I was once in attendance at an Auto Mechanics course at Technical College, dancing thru the hoops for a degree in Industrial Ed. One topic we kicked to death in there was the subject of honing and ridge reaming cylinders. It all came about when the instructor greeted us one morning with the news that you should *never* hone cylinders except to finish a bore job, and that it's *pointless* to ream ridges, unless you need to get the piston out. (Cars)
What an uproar! Most of us had had a fair amount of experience with engines, and we were pretty incensed. You *have* to "deglaze," or the rings will never seat! You *have* to deridge, or the new rings will hit the ridge and break on the first stroke! Everybody knows that!
Well, our instructor, who was a pretty savvy guy, knocked the wind out of the sails of the more scientifically inclined among us with one move: he handed out some reprints of actual SAE test results involving deglazing/not deglazing rering jobs, and ditto for ridge reams. It seemed that the compression test figures after 10000 miles were *better* by far for the unhoned engines. Also the increases in piston clearance were less, as was the bore wear, and - get this - they also showed *significantly* less bearing wear.
How come? Well, it seems that when you scuff up a perfectly good smooth cylinder with a rude sort of carborundum device, you are in fact only putting scratches on it, giving us a new, larger diameter at their base - sort of like root and pitch diameters in a nut, say. And when you put it back together, the new rings and this rough surface proceed to grind each other down until smoothness is re-attained. By this time, needless to say, you have larger ring gaps, due to more ring wear, and more piston clearance, since the cylinder has been taken down now to the base diameter of the honing scratches. And the valuable metal so removed has been converted into grinding compound circulating in your oil, so you have also reduced the size of your piston, and contributed significantly to wear of all the other parts as well, from rocker bearings to cam bearings to timing chain rollers to rods and mains.
Proven. Scientifically demonstrated in an actual SAE sponsored research project. But you gotta *deglaze* or the rings will never seat, correct? Well, yes and no, Chet. Although it is true that *chrome* rings are so hard and smooth that it can take from a long time to forever for the cylinder to wear them to perfect fit, this is *not* the case for Cast Iron rings. In fact, that's the secret. Chrome rings only in rough (honed) bores. And hone bores only when you have to, ie as the final "finish" of a bore job. Since the boring bar tool in effect runs a screw thread down the bore in its journey toward the land of largerness, it is necessary to do a final "polish" with a somewhat cruder tool - the hone. This is the *only* reason to put a hone in a cylinder. And when it's done, the machinist has purposely left some extra meat in there for the hone to finish to final diameter. And the final diameter is a tad small as well, in anticipation of the initially rapid wear that is inevitable as the new rings and the scratchy bore get acquainted. This is also the reason for very careful cleaning of said bores before assembly, and for very frequent oil and filter changes, until the motor has stopped manufacturing grinding compound during the
break-in process.
Back to re-ring jobs. Turns out there is just plain no reason to muck up that lovely smooth bore with a hone. None. Cast Iron rings will seat just fine on a smooth bore. And wear a lot less in the process. Ditto for the bore. So check the clearances, select the new pistons option if you like, and be sure to use Cast Iron rings. But don't subject your engine to a bearing grind job just because your mom always told you to hone your bores. It's silly.
I imagine this will shake up a few readers of brit-iron. I know it shook up me and my classmates that fateful day in '69. But I rebuilt my 544 Volvo in that class that year, and followed the prof's advice. And it seated its rings just fine, in a few hundred miles. And I haven't honed a cylinder on anything since - probably 30 or 40 rebuilds later.
And I've never had rings fail to seat. And I know all those engines lasted longer than they otherwise would have. In fact, I put 117,000 miles on a 235 Chevyvan rebuilt this way. The van was into its 200K range when I did @and it burnt no oil (<1qt/1000) when it finally rusted its way to the big Toyota factory in the sky."
Länk: http://home.clara.net/captain.norton/cnn3sec25.html
Fast jag kommer nog hona ändå...kanske.. :shock:
