.010 oversize

[GARY F]

When someone says they put .010 oversize rings on pistons , where is the extra .010  at. ? Is it on the length of the ring so the gap between the ends are less than  than standard ring?  Thanks for reading

[joe_padavano]

36 minutes ago, GARY F said:

When someone says they put .010 oversize rings on pistons , where is the extra .010  at. ? Is it on the length of the ring so the gap between the ends are less than  than standard ring?  Thanks for reading

 

The normal operation of an engine causes wear on the cylinder walls in the block. This wear can be out of round or taper over the length of the cylinder or both. With the exception of heavy duty engines that have replaceable sleeves in the cylinders, the only way get the cylinder back to a, er, cylinder, is to remachine the block. Normal engine blocks will have sufficient material to allow at least one such "overbore". In the case of your 0.010 over example, that means that the cylinders were machined 0.010" larger than the original factory dimension. This requires matching oversize pistons and rings. The gap of the ring is held constant. The circumference grows by the amount of the overbore times pi.

[GARY F]

Thanks Joe for the reply. You cleared up of what I was thinking.

[Gary_Ash]

Actually, Joe, in this case, I think Gary F. is referring to using oversize rings in an engine without boring.  It's kind of a cheap and dirty way to keep an engine running that doesn't have scored walls or a whole lot of wear.  The rings will need to be gapped by pushing the ring into the bore below where they normally travel and a feeler gauge is used to measure the gap.  Based on the ring manufacturer's recommendations, the gap may need to be adjusted by filing.  Of course, the bores may no longer be round, so sealing isn't perfect but maybe better than before.  In the bad old days, old pistons got knurled to take up some of the wear.  Sounds OK for a bore .010" or less over size, maybe not practical at .030" or more, but maybe someone here has done this trick.

[Bloo]

It was done with "file fit" rings, and those may have been less than .010 over the bore size in practice. I think .010 may have been considered a bit much. If you file a ring too much to get it in a smaller bore, it gets less round.

 

The ring gap would have to be set with the ring down at the bottom of ring travel to be sure it would not be too tight at the bottom and break. The gap at the top would be too loose because of the taper, but not as loose as standard rings.

 

This is rarely if ever done today.

 

[Ben Bruce aka First Born]

11 hours ago, Bloo said:

It was done with "file fit" rings, and those may have been less than .010 over the bore size in practice. I think .010 may have been considered a bit much. If you file a ring too much to get it in a smaller bore, it gets less round.

 

The ring gap would have to be set with the ring down at the bottom of ring travel to be sure it would not be too tight at the bottom and break. The gap at the top would be too loose because of the taper, but not as loose as standard rings.

 

___"This is rarely if ever done today."

 

 

 

Like Bloo said, but that was done a lot back in the 50's.    I expect for a lot [most?] of cars today it would suffice.  No, not perfect, but perfection is unneeded when only driven a thousand miles or so for show.

 

  Ben

[joe_padavano]

15 hours ago, Gary_Ash said:

Actually, Joe, in this case, I think Gary F. is referring to using oversize rings in an engine without boring.  It's kind of a cheap and dirty way to keep an engine running that doesn't have scored walls or a whole lot of wear.  The rings will need to be gapped by pushing the ring into the bore below where they normally travel and a feeler gauge is used to measure the gap.  Based on the ring manufacturer's recommendations, the gap may need to be adjusted by filing.  Of course, the bores may no longer be round, so sealing isn't perfect but maybe better than before.  In the bad old days, old pistons got knurled to take up some of the wear.  Sounds OK for a bore .010" or less over size, maybe not practical at .030" or more, but maybe someone here has done this trick.

 

Wow, seriously? With the motor that far apart, you just put in larger rings? Sounds kind of half-fast to me. Yeah, maybe if the engine in question has unobtanium pistons, but, wow! Sounds on par with putting shims behind the main bearing shells.

[Matt Harwood]

If you have an engine apart sufficiently to replace rings and find that you need to go oversize, you should do it correctly as Joe describes. New oversized pistons and rings with a correct line bore, not just a hone. Costs more but then you'll never worry if your halfway-adequate repair will give up when you're driving. At that point you will need to do it all over again, except the second time will be even more expensive because when it lets go it'll take a lot of other stuff with it, maybe even the block. Doing any job halfway is ALWAYS more expensive in the long run. If you're doing old cars and trying to save a buck, you will have nothing but misery.

Jesus, can you imagine if you bought a car and started driving it only to have the engine take a dump on you? When you take it apart and find some guy did it halfway out of ignorance or cheapness. I see that all the time and it makes me murderous. Please don't be that guy.

 

Doing it right the first time is always cheaper, even if it doesn't seem like it from this side. Plus you get a car that drives better and doesn't give you worries. What's the price of peace of mind?

[Restorer32]

What Matt said !

[trini]

Matt and I are like minded when it come to repair. If any of my friends does that kind of half a@#%se  job I will not speak to him again.

[Rusty_OToole]

It was a common repair when car engines wore out faster and were easier to fix. You could take a car with 70,000 or 80,000 miles on it that was burning oil, grind the valves and knurl the valve guides, hone the cylinders and fit .010 over rings, as long as the bore was tapered less than .010. It would run as good as new for another 30,000 miles or so and by then it was ready for the junk yard anyway.

Such an overhaul could be done for under $100 vs $300 for a rebuilt motor. Many cars were kept in service this way that would otherwise have been uneconomical to repair.

[Bloo]

This OLD method needs to be taken in context. It is not necessarily a halfassed job. Old cars required more frequent overhauls. Old cars used a LOT more oil normally than current ones do. You only get so many bore jobs before you are all done.

 

If it were me, and the block were out of spec (the manual will give a wearlimit for taper), I would bore it and put in some high-quality Ross, Arias, etc. lightweight pistons with a MODERN low-tension ring package that will control oil better, and not wear out the bores right away. 

 

On the other hand If you are going to shove some period-correct NORS four-ring pistons in there, with rings as thick as a yardstick, it is certainly questionable whether to waste one of your potential bore jobs on that.

 

On the old prewar (and early postwar) splash-lubricated Chevrolets, as an example, it was pretty common for them to have TWO minor overhauls before they got to 100,000 miles. Read the archives over on the VCCA forums if you don't believe me. There is at least one regular poster over there with dealership experience going back to 1950 or earlier. Would you want to give up 2 of your allotted bore jobs to get 100,000 miles? Even one? I wouldn't.

 

No doubt someone will say "But I'm not going to drive it enough to wear it out!". To each his own, but that makes me bristle. That excuse has been used to justify some of the crappiest work I have ever seen. Cars that don't get driven have MORE trouble, not less.

 

It is extremely unlikely that I will ever find myself file-fitting rings. On the other hand, If I had some engine in front of me with the ORIGINAL pistons, and they were in excellent condition, and the skirt clearance was ok, and the groove clearance was ok,  and the taper was only a couple of thousandths out of spec, and when I shoved a new ring down the bore, the gap was way too wide..... Yeah, I'm not going to rule it out. Why trash original parts over a couple thousandths of bore wear?

 

Back in the day, they use to let things go much farther than a couple of thousandths over wearlimit. The sky didn't fall. Puppies didn't die The sun still came up in the morning.

 

They used to knurl pistons, too.

 

Context is everything.

 

Edited December 17, 2019 by Bloo (see edit history)

[Ronnie]

17 minutes ago, Bloo said:

This OLD method needs to be taken in context. It is not necessarily a halfassed job. Old cars required more frequent overhauls.

 

I totally agree with this. When I was a young man, about 50 years ago, I worked at a garage that had a fully equipped automotive machine shop. We could grind cranks, bore blocks, do valve jobs.... simply put we could do everything that needed to be done to an engine to rebuild it.  Still with all the automotive machine shop equipment it was not uncommon for us to do an in-the-car overhaul of an engine. Usually in-the-car overhauls were done on older vehicles for people that might have limited ability to pay and the owner of the garage was trying to keep the cost down for them.  Or maybe the car wasn't worth spending the money for a full overhaul. 

 

We would pull the oil pan, sometimes having to jack the motor up to get the pan off.  We would remove the head and do a valve job on it.  We honed the cylinders to get them straight and break the glaze and installed new rings - oversize rings if needed.  We had a ring grinder to fit the rings in the bore instead of filing them by hand.  It looked like a tuna can with a hand crank on the side and a small grinding wheel sticking out the top.  When we got done with an in-the-car overhaul the owner could get a lot more miles out of an old car without having spent a lot of money on it compared to doing a full engine overhaul that requires pulling the engine out and tearing it all the way down.  I wouldn't call that half-assed if it got an old car back on the road that might otherwise have been left sitting in the driveway due to the owners lack of funds to do a full overhaul.  

[trini]

Fixing the top end  will create a problem for the lower end of the engine. How about ?

[Ronnie]

38 minutes ago, trini said:

Fixing the top end  will create a problem for the lower end of the engine. How about ?

I'm not sure what would create the problem with the lower end by replacing the rings and grinding the valves but you might be right.  I remember helping do several of the in-the-car overhauls and I don't remember there being a problem with the lower end but that was a long time ago. It was possible to install new crankshaft bearing in some of the old cars without pulling the engine. 

 

[Bloo]

Bearings in those days were typically babbitt with shims. Those would have been checked and adjusted at the same time. For cars with inserts .001 and .002 undersize rod bearings existed for cranks with a little wear. The crank had to be checked for roundness. You can't fix out-of-round with a bearing.

 

You have the rods out if you have the pistons out. I guess you could skip the mains (I wouldn't), They are less likely to be screwed up than rods.

[Ronnie]

 

You are correct. If the crank checked good, bearing inserts in the rods and mains could be replaced if needed on some engines. If I remember correctly, we only replaced the bearing if needed when doing a in-the-car overhaul.  The goal was to save money.

 

Once all the main bearing caps are loose you can remove one main bearing cap at a time and install new bearing inserts in the block by running the insert around the crank using a plastic tool made for that purpose.  You could also do the same with the rear main seal on some of the old cars that had two piece seals. Seems like there was a tool that pulled the seal around someway while turning the crankshaft.  Maybe that was on the engines that had the rope type rear main seals.  It's been so long I don't remember how it worked for sure.

[trini]

I was really referring to cars with shell bearings. If, say, I am removing the head(s) of a GM engine and doing a valve job, removing the pistons which requires removing the rods to get the pistons out. Let us refer to an engine with 80000 miles, to hone the block the shavings will infiltrate the crank bearings. Are the rod bearings in good shape ?   The crank bearings may or may not be in good shape. So I reinstall the old bearings to save money. When I hone the bore and install new rings I will be getting some more horses,  ( increase compression) which will put some more downwards pressure on the old bearings of the crank and rod bearings. I personally do not think it is a goo job unless I want to get rid of the car.  Some sucker will be stuck. 

Babit  bearings are easier to service. I have seen guys use the brown cloth to polish the crank  then use  prusian blue  to check bearings fit and scrape the bearings with a scraper to fit. This is just my thought.

  

[Ben Bruce aka First Born]

On 12/16/2019 at 3:16 PM, GARY F said:

When someone says they put .010 oversize rings on pistons , where is the extra .010  at. ? Is it on the length of the ring so the gap between the ends are less than  than standard ring?  Thanks for reading

 

 

  YES!

 

  Ben

[PFitz]

50 years ago and more, back when these cars were newer, they were just everyday transportation. It was common practice to just do an "engine overhaul". What some today may think was cutting corners, but it was a common option by the local garage presented to customers to save them money on their daily driver. And it could all pretty much be done with hand and bench-mount tools in a "service station" without need of a big investment in having an engine rebuilding machine shop.

 

So, in addition to just clean up the cylinders and using oversized rings, it was accepted practice that worn pistons were knurled instead of being replaced. And, valve guides were knurled instead of sleeved with bronze. While it didn't make for a motor with a new, long lifetime, it was enough to stop the white clouds coming out the tailpipe  until the customer was ready to replace the car.   But there are some who roam the earth that still think that way about collector cars.

 

Paul

Edited December 18, 2019 by PFitz (see edit history)

[Frank DuVal]

21 hours ago, Ben Bruce aka First Born said:

On 12/16/2019 at 4:16 PM, GARY F said:

When someone says they put .010 oversize rings on pistons , where is the extra .010  at. ? Is it on the length of the ring so the gap between the ends are less than  than standard ring?  Thanks for reading

 

 

  YES!

 

  Ben

?????

 

Oversized on pistons is diameter, not length.....

 

If a standard bore is  3.4375", .010" oversized makes the bore 3.4475"

 

and a .020" oversized would be a bore of 3.4575"

[Bloo]

29 minutes ago, Frank DuVal said:

Oversized on pistons is diameter, not length.....

 

If a standard bore is  3.4375", .010" oversized makes the bore 3.4475"

 

and a .020" oversized would be a bore of 3.4575"

 

This^^. An .010 oversize ring is for a bore that is .010" larger than standard, it is not an .010" difference in ring gap.

[PFitz]

Correct. !

 

If it was ring length then you'd have to divide that by 3.1415 to convert that to finished bore diameter, or to match up to a set of pistons. And that would make for the risk of measuring  and parts ordering confusion. There's enough chance for getting it wrong without making it more complicated. 

 

Paul 

[Bloo]

I don't really agree with the characterization that a minor overhaul (without boring) was simply a "cheap" option to keep an old junker alive. Yes it cost less. The example I gave above where a couple overhauls occurred before 100k miles was pretty typical in the 20s and 30s. Then the war came. Don't forget how completely worn out most prewar cars are due to the unavailability of new cars (and parts) during the war. Can you imagine if everyone re-bored every time? There wouldn't be any usable blocks left today.

[trini]

Boring out blocks  became popular in the cars and trucks of the late fifties and through   sixties.

[Matt Harwood]

I don't know that anyone is arguing that back in the day this wasn't a reasonable low-cost alternative to keep a car running a little longer when it was being used as daily transportation. However, I do think that today there's not much excuse for doing half a job and it does seem like corner-cutting on a collector vehicle. If you're going far enough to tear the engine down to get the pistons out anyway, it really is almost easier to pull the whole engine and do it right. I know I'd be very unhappy if I bought a car with an "overhauled" engine and it had an engine failure where I discovered the last guy only did the barest of minimums to get it running while simultaneously calling it "overhauled." Technically, yes that's what an "overhaul" was, but in today's world I think that's a bit of a misnomer.

 

If you're playing this game, cutting corners isn't OK anymore. Today we know better and expect better and if all you can afford is this kind of repair, you should not expect it to be a permanent solution. You should possibly even expect a future owner to come back angry with you. I've yet to see a halfway solution that was the right choice on an old car of any kind.

[Ben Bruce aka First Born]

Matt, I think we are talking apple and orange here.  

  I don't know about anyone else and where they were raised, just that in Missouri where I came from rings bearings and valve job was a NORMAL thing.  A lot less work than pulling the engine, TEARING THE ENGINE COMPLETELY DOWN for the machine shop, waiting until said shop could get the job done and reassembling.  I did many 216 Chevrolets in one day. The farmer was happy.   Buick engines two days.  I drove my 1950 convertible another 40,000 miles and it was still running like a top when traded.  Thanks to "chrome" rings and better oil.  I realize we are talking collector cars here, but how many years would it take us to put 40,000 miles on one? I have only done 20,000 in nine [9] years. Many do not do that much.

 

  Ben

[Ben Bruce aka First Born]

1 hour ago, Frank DuVal said:

?????

 

Oversized on pistons is diameter, not length.....

 

If a standard bore is  3.4375", .010" oversized makes the bore 3.4475"

 

and a .020" oversized would be a bore of 3.4575"

 

 I KNOW that.  I may be wrong, the ring manufacturer had to add metal somewhere. I never measured one, but bet it was in the length of the piece of steel he made the ring from. Not the thickness.  In other words, if one measured a standard and an oversized ring from one end  [ at the split opening ]  around the outside circumference to the other ,one finds the difference. If I am wrong, the donuts are on me.

 

  Ben

[Ronnie]

I think the definition I found on the internet (below) pretty much explains the differences between the two types of engine work we did in the garage where I worked back in the day.

 

" A "rebuilt" engine should be put back into like-new condition, with all parts examined and replaced if they aren't within new tolerances. An "overhauled" engine has new parts installed when they are worn beyond limits, but many are left in place because the wear limit hasn't been exceeded. "

 

I think today's car collectors would prefer a car that has a "rebuilt engine" even if it does cost more, but that was true 50 years ago too.  When I was working at the garage I talked about earlier, we rebuilt a lot of engines for Pop Rice of Peggy Craft Restorations who restored cars for the likes of Howard Baker Jr., Harold Coker and many other prominent car collectors of the day.  They didn't ask what it cost. They just asked if you could do it. 

 

On the other hand there were customers who would come in and ask if they could get their cars overhauled so they would have a decent car to drive to work. Sometimes they would ask the boss if he could do it on a credit and let them pay a little on it each week. If he knew them he was usually nice enough to help them out. Yes, they got an in-the-car overhaul as I described before but they were very happy with the results.  Their cars no longer looked like James Bond's car going down the road with the smoke screen turned on and they weren't having to stop every other day at the cut rate gas station to buy "bulk oil". You remember bulk oil don't you?  

 

 

Edited December 19, 2019 by Ronnie (see edit history)

[Rusty_OToole]

I have some old MoToR Magazines from the thirties. This was the garage trade magazine of the time. In one 1937 issue there is an article on selling overhaul jobs. They say an overhaul or ring and valve job is typically needed at 20,000 to 30,000 miles. This seems short to me but that is what they said. They were talking about early thirties cars with no oil filter and poor air filter, cast iron rings, and oil and metallurgy  inferior to today's cars. There is such a thing as progress.

 

The advertising pages were full of ads for piston skirt expanders, special rings for tapered cylinders worn over .010 and other devices. There were "10UP" rings, "Cord" rings that resemble a Slinky. Chrome piston rings were not available, they were a WW2 development along with other things like better oil, filters and additives that doubled engine life after the war even on motors that looked the same as their prewar counterparts.

[Gary_Ash]

I found this blog about fitting piston rings, has some interesting info.  It would appear to be worthwhile in any engine ring job/rebuild/overhaul to check the ring gaps and set them correctly.

http://blog.wiseco.com/how-to-file-fit-and-install-piston-rings

 

I use to work on cryogenic refrigeration engines that looked like small, 1-cylinder piston engines with 1" to 1.5" bore and operated on 400 psig pure helium.  The seals were made of Teflon and cut like piston rings.  They had to run dry, since oil would freeze at the operating temperatures of -440 °F (10 Kelvin).  A good seal could survive 30,000 hours or more of operation at 72-144 rpm, unlubricated.  Next time you get an MRI done, there will be one of these little engines running in the adjoining room to keep the superconducting magnets cold.  To make better seals, I dug into some old literature about piston rings, found out that most of the technical issues had been resolved by the steam engine guys back in the 1850s-1880s.  Think about the actual shape a ring needs to be ground to so that it will be exactly circular when compressed in an engine bore - it's not a circle.  As a cylinder gets bored out, the new rings have to be cam-ground so that they become round at the new bore diameter.  It was interesting to learn that, as in car engines, a lot of the force to keep the ring seated on the cylinder wall comes from gas pressure behind the ring.  So, that gap in the ring needs to admit some gas, but the ring has to seal pretty well top and bottom as well as against the cylinder wall. 

[PFitz]

1 hour ago, Ronnie said:

I think the definition I found on the internet (below) pretty much explains the differences between the two types of engine work we did in the garage where I worked back in the day.

 

" A "rebuilt" engine should be put back into like-new condition, with all parts examined and replaced if they aren't within new tolerances. An "overhauled" engine has new parts installed when they are worn beyond limits, but many are left in place because the wear limit hasn't been exceeded. "

 

I think today's car collectors would prefer a car that has a "rebuilt engine" even if it does cost more, but that was true 50 years ago too.  When I was working at the garage I talked about earlier, we rebuilt a lot of engines for Pop Rice of Peggy Craft Restorations who restored cars for the likes of Howard Baker Jr., Harold Coker and many other prominent car collectors of the day.  They didn't ask what it cost. They just asked if you could do it. 

 

On the other hand there were customers who would come in and ask if they could get their cars overhauled so they would have a decent car to drive to work. Sometimes they would ask the boss if he could do it on a credit and let them pay a little on it each week. If he knew them he was usually nice enough to help them out. Yes, they got an in-the-car overhaul as I described before but they were very happy with the results.  Their cars no longer looked like James Bond's car going down the road with the smoke screen turned on and they weren't having to stop every other day at the cut rate gas station to buy "bulk oil". You remember bulk oil don't you?  

 

 

 

 

There are many car owners in the hobby who don't have the deep pockets for  a full engine rebuild. Especially when they are looking at that will cost them three, four times what they paid for the car.  They just want to get their toy to run, be fun, and get them back home. Not much different than 50-60 years ago. 

 

And yes I remember bulk oil and I remember some gas stations had glass bottles of "rejuvenated oil"...….. often bought by customer's with cars that had engines so worn out that they almost burned more oil than gasoline. …………….. like my hand-me-down 62 Chevy Biscayne. Always started, never died, but if it burned anymore oil it might have qualified as a diesel. ☺️

 

Paul     

Edited December 19, 2019 by PFitz (see edit history)