Jump to content

Help Me Further Understand Top End Engine Wear


keithb7

Recommended Posts

I do grasp valve guide wear. If your intake valve guide has wear, when it's open, the piston can draw misty crankcase air in around the valve stem, up the guide and into the cylinder. I believe this is especially present when the throttle valve is closed. The piston being forced down, is trying to suck in air. It can't get much through the closed off venturi. Vacuum created in the cylinder will pull air form anywhere. So at this point it can really draw air though any worn valve guides. Real world road conditions have this occurring when going down a hill. Car in gear. Gravity pulling the car down the hill. Drive wheels are forcing the crank around. Throttle valve is closed. Some blue smoke will often be seen out the tail pipe. When the road levels off, you hit the throttle open. A larger amount of blue smoke shoots out the exhaust. The smoke n cleans up and disappears.

 

Under normal driving and acceleration, smoke may not be seen. Little, if any crankcase oil comes up the valve guides. Am I on the right track here? Valve guide wear, I assume can be a result of worn valve seat surfaces. Skewing the valve off of true vertical? Or possibly worn tappets or valve stem ends where they meet. Again, knocking the valve stem off true vertical. It starts out ever so slightly and compounds as items wear more and more.

 

My question is, can misty crankcase air be drawn in to the cylinder by way of a worn exhaust valve guide? My suspicions are, not normally. Or maybe not a lot. If the exhaust valve is seated properly, and is sealed up, when the piston is sucking in air, the exhaust valve is closed. Air is not drawn in, past it.  The exhaust valve is mainly open when spent gases are ejected out. There are some brief periods of valve overlap.  New A/F is drawn in while the exhaust valve is still open. Perhaps crankcase air can be drawn in from the exhaust valve guide at his very time of overlap? Just not as much as a worn intake valve guide.

 

I am digging into my 1938 228 ci 25" engine this winter. So far the head is off and I have felt some exhaust valve guide wear. I suspected this. Today my suspicions are confirmed.

I also found some rust at the tops of the cylinders. Mainly the left side of the cylinders. Near the top, but down low enough, past the top rings. I would have thought 1500 miles this summer would have removed this rust. Not so it seems. Perhaps my top rings have excessive end gap, indicating wear. I wonder why this rust is  not present on side of the cylinder right below the valves? Wet damp incoming air from a high humidity area where it lived and was driven over the past 80 years? Humid air with the engine sitting for decades with little use? Allowing for rust? 

 

 

 

 

IMG-7329.jpg

Link to comment
Share on other sites

Another pic from this morning...1 head bolt snapped off at removal. I'll drill and extract it soon when the engine is pulled and on a stand.

Seems to me that cylinders 1, 2 and 6 had the most damp oily residue. Incidentally, those cylinder's exhaust valves also displayed the most valve guide or stem wear.

 

228 Top end.jpg

Edited by keithb7
Link to comment
Share on other sites

#1 seems to have the most rust present. The scrape seen is from my fingernail. Almost looks like a crack near the top of the rust line. Just the edge of the rust I suspect. I had no symptoms that would lead me to believe this was a crack.  The engine ran very well and made 95-100 psi dry or wet across all cylinders. I am quite interested to measure top compression ring gap to learn more.

 

#1.jpg

Edited by keithb7
Link to comment
Share on other sites

Using my dial bore gauge set to zero 3.375 I get 0 at the top, inside the top ridge. Dropping just below the ridge I measure about a 0.012 to 0.014  larger bore.

 

I took a scotch-brite pad to the rust seen in the photos. It easily polished off and the bore looks much better. I guess I was just rust from humidity in the air in my garage. The engine hasn't run in 3 weeks. I recently began using a propane heater a little. Propane heat is humid. My guess is that is what happened to create the rust on my cylinder walls. #1 below. 

 

 

B0CD2D40-393A-448E-876E-A666696E56EB.jpeg

Edited by keithb7
Link to comment
Share on other sites

My experience is that worn valve guides (or worn seals in an ohv engine) show up most often as a puff of white smoke when first start, or when pull away from lights after idling a while, or when decelerating. So I support your comments. I had a 6 cyl Falcon that had done over 300,000 km that did that. I eventually had to take head off to decoke and there was no appreciable wear on bores, you could still see the original machining cross hatching on the non thrust side of the bores. So I have always figured a bit of oil at startup is a good thing for wear!

 

When I had my 29 flathead rebuilt, I foolishly asked them to re-bush the valve guides. I soon had major loss of compression and I found they had split all the exhaust guides which caused valves not to seat. So VERY bad wear can do that but would not normally expect it. Valve guides are cheap and relatively available from all normal sources. I changed mine using a suitable high tensile bolt, short lengths of tubing and heavy washers.

 

That rust is strange and I dont think it is related to valve guides. You have a lot of wear in top of cylinders. Maybe high humidity and cold weather could combine to cause condensation when stored. I have never seen it in a running engine, just in lots of decrepit ones!

Link to comment
Share on other sites

Thanks for your comments @westaus29. I just came in from my shop. Measuring with a dial bore gauge. This block is definitely stock bore still. I get about .010 taper from top of cylinder to the bottom.  Well beyond spec. Max taper in the shop manual for a new engine is 0.0015

 

Not quite what I'd hoped. Yet the learning experience for me has been awesome. Now I have to decide on my next steps. The engine ran pretty well before as mentioned. I'm not convinced yet to go full out and rebuild this engine with all necessary machining. Wondering if I could get away with a new set of rings. Hone the bores. Some new valve guides and lap the valves. A few other items. Probably get many more years out of it, fair weather cruising around town. 

Edited by keithb7
Link to comment
Share on other sites

Sometimes it’s best to let sleeping dogs lie. However, you have woken the dog and looks like some work ahead. 
 

Many years ago and lots of miles ago, I had a miss in my ‘53 Plymouth engine. It had about 72,000 miles on it at the time. Head was pulled and as suspected number 6, with low compression, had a burnt intake valve. Replaced with a good used valve and lapped the rest. 
 

There was some ridge in the cylinders so reamed it out and pulled the pistons which looked pretty good. Honed the cylinders, new rings, and reassembled. Bearings were plastic gauged and were within factory specs so were re-used. 
 

Everything was re-assembled with new head gasket. Engine presently has 103,000+ miles, so more than 30,000 miles since its refreshen. Oil pressure is great, compression still impressive, and it doesn’t burn oil. Surprisingly the engine leaks very little oil even though all seals are original.

 

I’m guessing you could do something similar and get many happy miles. I don’t plan on touching my engine again unless required. However, your engine and your call. Good luck with whatever you decide. 

Edited by RobertKB
  • Like 1
Link to comment
Share on other sites

Thanks for your experience @RobertKB. I am considering the route you describe. Sleeping dogs lie, yes I could have. I wanted to get in there and see what I really had. I wanted a rewarding winter project that would keep me busy and stimulated. It's too quiet, cold and dark around here all winter! The kids are gone. Covid has us locked up. I look forward to this.  There are a few other issues with the engine that I need to deal with too. Replace all expansion plugs. One is weeping considerably. While the engine is out, flush out about 2-3" of rust scale that I discovered in the bottom of the block. Replace the rear seal and front motor mount. A couple worn valve guides. Lap all valves....It all sounds great until I expose more and more, the deeper I go. 

Edited by keithb7
Link to comment
Share on other sites

Pull the pistons...check out those rings.

I think it sat for a long time in a damp environment.

Upper rings aren't sealing/working very well at all.

  • Like 1
Link to comment
Share on other sites

Looks odd.  As Dodgeb4ya stated: top rings aren't sealing very well.  I'd be tempted to scotchbrite as you did and with inside micrometers try to get a diameter measurement from the rusty side and also 90 degrees from that.  Trying to determine if the bores are "egg shaped" in any way.  Perhaps carbon black, marks alot, or dykem the upper 1 inch of the bore circumference and rotate the crank to see what kind of scraping/sealing action your getting from the upper rings.  Might all be good information but if it was running good before your teardown I'd probably button it up and continue driving it. Regards.

Link to comment
Share on other sites

I really want to check my engine after un-sticking it. But it runs decent. Had oil pan off twice. First time was to clean and inspect bottom end, second time was to replace timing cover seal and gaskets. 
oil stays clean, but it hasnt left the yard yet. I run it often, as its in and out of shop almost every weekend. 
 

the suggestions that top rings arent sealing may be right on the money. 

Link to comment
Share on other sites

Was a compression test done recently?

Read that it was....odd that compression was so high on those rusty cylinders. 

Looks like the compression  rings are hardly scraping the rust.

Edited by Dodgeb4ya
Link to comment
Share on other sites

@Dodgeb4yaI performed a couple of compression tests. Most recent was in April this year. I was getting 90-100 across all. Very small difference between wet or dry.  The car performed well all season. I put about 1575 miles on it in 2020 crusing season.  Then I parked the car in early Oct.  It's been sitting in the garage ever since. As the weather turned I have been using a propane fuel heater to heat up the garage. Propane heat is quite humid. The humid air perhaps created this light corrosion seen on the cylinder walls. When I took a piece of Scotch-brite to it, the rust easily came off. The raw steel on the cylinder walls could start to oxidize quite quickly I suspect. As seen in my photo above the cylinder wall cleaned up nicely. ...Just a theory.

 

I do plan to slip out the pistons and inspect. The top compression ring could be worn and not sealing. Could be broken too, floating in its groove. We shall see. The temptation to bore over this current engine 1/16",  from 3 ⅜"  to 3 7/16" bore is nagging at me. This 4 1/4" stroke engine with a 3 7/16" bore would net me about 237 ci. Vintage Power Wagons sell 3 7/16" piston kits with rings for $185/set. Seems like a really good price. Would really wake up this little '38 car. Would there be any concerns with re-using the original con-rods, crank and related (if all test well) with the new 3 7/16" bore pistons?

Edited by keithb7
Link to comment
Share on other sites

Now we finally know what Marvel Mystery oil was for.  It prevents or discourages top of ring rust when you park in a propane heater space.  But wait if the mmo is in the intake mix it burns off, and if it's in the crankcase oil it never gets past the rings.  So I guess it's still a mystery!!!

  • Like 1
Link to comment
Share on other sites

the biggest eaters or the bore are cast iron rings.

 

I tried to find off the shelf moly rings for the small flathead to no avail. 

 

The Freewheeling Tony Smith has had modern Ross pistons and thin moly rings made for them in the past, I dunno if he sells parts or not though.

 

If I end up rebuilding my flattie I'll be asking him.

 

https://www.facebook.com/thefreewheelingtonysmith/posts/3017418274946075

Link to comment
Share on other sites

I have been doing more research on this cylinder corrosion. I looked at some pistons removed from a 1949 218 ci Canadian engine that I pulled apart last year. It happens to also be a 3 3/8" bore. Pretty much exact same engine this 1953 228 ci engine except the stroke length.  My 228 is 4 ¼" stroke, the 218 os 4 1/16" stroke.  The 218 utilizes 4-ring pistons. I assume my 1953 228 does as well. I have not gotten that far into my 228 yet to verify. The used pistons I pulled out of the 218 have several broken top rings. I was told that the 218 was running when it was pulled. How good? Who knows.

 

This makes sense that my 228 may also have broken top rings.  I see that the corrosion is present in some cylinders but not all. The corrosion is mainly on the thrust side of the piston and cylinder. Straight across from the valves. Cylinders 4, 5, 6, have little to no corrosion present. If it were related to humidity in my garage, surely it would be present in all cylinders. Right?  That half baked theory is out the window. If the top compression ring is broken, then the 2nd compression ring makes a pretty good back up. Right? Engine would still run pretty good and make half decent power and compression.

 

If I choose to just hone and re-ring this engine I do need to ream the .010- 0.14 ridge off the top. Initially, I wondered why? The new rings would stop at the exact same location  a where the old rings stopped. At the same ridge, right?...Well yes and no.  The top piston ring and the cylinder are wearing in together. Perhaps a rounded edge has formed on the old piston rings. Nicely mirroring the cylinder wall wear. If a new ring, with a sharp nice squared edge on it is installed, and put into the cylinder, it could snag slightly on the top ridge.  The ring could transfer immense energy into the the surrounding piston groove and crack the piston land, and likely the new ring too. A ridge reamer can be had pretty cheaply, and used at home. Then cleaned up with a little emery cloth.

 

Next thought I had was ring gap. What if I used new .010" over sized rings and gapped/filed them myself? That could work. New rings would have to be gapped at the bottom of my cylinders as there is about .010 of cylinder wall taper. If gapped at the top, they would become too tight at the bottom. Again maybe breaking a ring.

 

Interesting stuff. All just musings and ideas for me at this point. Sure is fun to learn about though! I can tell you that no matter what I end up doing with this engine, any money spent will have been very well spent on my education. Not on cigarettes, booze, gambling, or some other waste of time. LOL.

 

 

Link to comment
Share on other sites

2 hours ago, Sniper said:

the biggest eaters or the bore are cast iron rings.

 

I tried to find off the shelf moly rings for the small flathead to no avail. 

 

The Freewheeling Tony Smith has had modern Ross pistons and thin moly rings made for them in the past, I dunno if he sells parts or not though.

 

If I end up rebuilding my flattie I'll be asking him.

 

https://www.facebook.com/thefreewheelingtonysmith/posts/3017418274946075

One poster here has had custom pistons made that use a standard ring for a modern engine of the same bore.  A little expensive for my taste but and elegant solution.

 

But, if one was building an engine for long term use, that is the best solution.

Link to comment
Share on other sites

3 3/8 bore engines were used in Canada until 1955.  They were not as widely used in the USA.  It has been difficult to buy new 3 3/8 bore pistons for 30 years or more but the standard 3 7/16 piston is the same as 3 3/8 + .060.

A change in the width of the top ring was made postwar and this will play nicely into your overhaul.  

If you can get an early set of 3 3/8 standard rings, you will find the top ring is too wide for your mid 50s pistons so you have a machinist reprove the top land to fit the earlier top rings.  Regrooving top lands was done on any competent overhaul to avoid top ring problems . A Hastings GL spacer was inserted into the groove against the upper land so the standard width ring could be used.  Using the earlier ring set with the later pistons means you do not need the spacer.

Start looking for a standard 3 3/8 piston  ring set.  It could take some time.

Link to comment
Share on other sites

Thank you @dpollo.  Much appreciated. I was hoping That maybe looking for Canadian 218 rings might turn up results sooner than searching 228.

 

What do you think about going 1/16 over to 3 7/16 bore. A More common size.  Would the 3 7/16 pistons match up with my current con-rods? Any stress concerns?

Link to comment
Share on other sites

If you end up just honing and ringing the engine........a couple of points. Make sure your used pistons are in good condition. No point in using any piston that is slightly suspect. 
 

Reaming the ridge out is done for the reasons you mentioned but also for making piston removal easier. Even a slight ridge makes the rings hang up and can cause damage to the piston. 
 

Once caps on the con rods are removed put some masking tape on the bolts to prevent even the slightest marking of the crank upon removal. Same when you reinstall. 

  • Like 1
Link to comment
Share on other sites

For the sake of more discussion around this topic: Here’s a photo of a piston from the spare 1949 CDN 218 3 ⅜” bore engine that I have.  Top piston ring has multiple breaks.  Is this fairly common? I suspect this occurs from excessive carbon build up in the behind and around the ring. Causing a tight squeeze and breakage?   


What causes excessive carbon build up, leading to broken rings? A poorly tuned engine. Incomplete burn if the A/F mixture. Crankcase oil entering into the cylinder.  Poorly carbureted AF mixture.  Improper valve clearance settings. Valve guide and valve seat wear. Piston ring wear. Improper warm up time before putting a load on the engine. Weak spark. Incorrect ignition timing. Low cylinder compression. Tapered or out of round cylinders.  Worn rings, excessive end gap. 
 

There are seemingly endless opportunities to have excessive carbon building up in behind the top ring groove. Causing possible ring breakage. 
 

 

B1B76A3F-534F-483E-A912-B72D6B6DE6FA.jpeg

Edited by keithb7
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.

Terms of Use