Cylinder honing?

[36tudordeluxe]

Originally Posted by rotorwrench

I'd want to know what the piston to cylinder clearances are. Different types of piston require different clearance specs ie forged require more & cast require less. Wrong specs will lead to problems. You will need to know this stuff even before you go to honing. If it's way loose, all the honing in the world won't make it better.

Cast pistons, cylinders measure 3.1225" and pistons 3.1185". Measured gap on one of the compression rings at .021" and I believe it should be around .013". Confused, piston to wall difference is .004" and I never filed fit the rings; how did I get such a big gap?

[Ronnie]

What was the gap when you installed the rings. Did you measure them yourself? Did the shop install the rings?

R

[flatjack9]

That's actually pretty loose for a cast piston. For every .001 change in cylinder diameter, your end gap will change a little over .003. .021 will not hurt you though.

[Ronnie]

The ring end gaps are set as minimums not maximums. To prevent ring butt due to heat expansion.

R

[Karl Wolf]

I have used Bon Ami cleanser as an alternative to engine disassemby, where the rings would not seat. The method: dust about a large tablespoon down the carburetor of a running engine. Do it slowly. DO NOT let it die.

I've done it twice, with success.

Karl

[36tudordeluxe]

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I installed the rings but don't remember what the original gap was, probably didn't even measure it at the time of assembly; can it change over time?

[Brian]

I installed the rings but don't remember what the original gap was, probably didn't even measure it at the time of assembly; can it change over time?
You're learning a bit doing all this - eh?
As Ronnie said, the ring end gap is set so that as the engine gets to operating temp, and things expand, the ends of the rings have sufficient gap to prevent them expanding so much that they hit each other, because after that the only way they can accommodate any further 'growth' is by moving sideways; then they'll break up! Rule of thumb for any engine is to give the rings 0.003-0.004 gap per inch dia of bore. Remember that!
So...[example]; a 4" bore, the gap is set 4"x .0.003 = 0.012 / 4" x 0.004 = 0.016.
Can it change over time?
Sure!! as things wear [cylinders and rings] the gap increases. [by pi the amount]
That is why, when re-ringing a worn engine [one with tapered bores], the ring gap is checked at the bottom of stroke.

[Ronnie]

Originally Posted by Karl Wolf

I have used Bon Ami cleanser as an alternative to engine disassemby, where the rings would not seat. The method: dust about a large tablespoon down the carburetor of a running engine. Do it slowly. DO NOT let it die.

I've done it twice, with success.

Karl

This is really a recipe for disaster. This process will produce the worlds best honing compound that will circulate through the engine and will soon produce full face contact rings giving you a ring that has reached the end of its service life.This practice will negate any of the cleaning of the engine components done before assembly.It is about the same as driving the car without an air cleaner.

Some good info here on keeping an engine clean before assembly
https://www.hastingspistonrings.com/...re-refinishing

R

[rotorwrench]

The old Bon Ami trick was used generally to try and reseat worn out rings on a smoker. It was always a last ditch procedure to get a person by till they can get an overhaul done. If new rings don't seat, there is generally something wrong with the set up prior to installation. Max clearance for the 8BA family of engines was .006" so at .004" clearance it's getting just a tad bit on the loose side for cast pistons but not too bad. It's not uncommon to set up Forged pistons loose due to the coefficient of expansion. A cast piston should be tighter but it may work OK at .004 to .0045 clearance after a clean up hone job. I've even used sandpaper by hand to break the glaze on a cylinder wall but the silicon carbide residue still has to be removed with a brush & soapy water. A person certainly doesn't want that hard material residue in there for a new ring break in.

[Bored&Stroked]

The end gap is a bit large, it may let a little compression through (as blow-by), but it would not be the cause of a major problem with compression numbers. Given that nobody can guesstimate what the rings were originally set at - doesn't really matter at this point. When you hone and put new rings in, follow the ring manufacturer's documents on end-gap - it will be specific to the type of rings you've purchased and potentially the application (naturally aspirated, supercharged, street/race, etc). Part of this will depend on the manufacturer and whether these are more modern rings that are used in a lot of applications.

I usually order 'file to fit' rings . . . as I specifically setup a ring set for every cylinder and I need the extra diameter amount (usually about .005 over a drop-in set) - so I have something to file.

[Ross F-1]

The only time I've seen compression test results in the 60-range was when there were valves not closing. My cylinders had 10 thou taper, ring gaps 30+, and I was still seeing 80 psi. In fact the engine ran pretty darn good.

[Bluebell]

here is something from left wing:
I was doing a compression test years ago and the valve failed part way through (got carbon in it I suppose?) Anyhow I put another schrader valve in it and it gave me readings only about half of what the gauge was showing earlier for the same cylinders.
Point being that the spring in the schrader valve for tyre valves is much heavier.
You need to buy the correct valve for your compression gauge.
It seems to me that this engine may have come apart too soon. not trying to critisize.
BTW. Ross recommend a 30 degree cross hatch and the use of a premium non synthetic, 20w 50 motor oil for run in (that is for their forged pistons)

[Ronnie]

Originally Posted by Bored&Stroked

The end gap is a bit large, it may let a little compression through (as blow-by), but it would not be the cause of a major problem with compression numbers. Given that nobody can guesstimate what the rings were originally set at - doesn't really matter at this point. When you hone and put new rings in, follow the ring manufacturer's documents on end-gap - it will be specific to the type of rings you've purchased and potentially the application (naturally aspirated, supercharged, street/race, etc). Part of this will depend on the manufacturer and whether these are more modern rings that are used in a lot of applications.

I usually order 'file to fit' rings . . . as I specifically setup a ring set for every cylinder and I need the extra diameter amount (usually about .005 over a drop-in set) - so I have something to file.

From the info supplied it appears to .060" over.
Purchasing a modern style not "nos" a file fit set for that bore size will be a challenge if not impossible.Order a new set and run what the end gap is and you will be fine.As stated before the spec's are for min not max.Cleanup and honing will get it done if followed diligently.

R

[Frank Miller]

As others have said the end gap is to keep the rings ends from butting against each other and breaking. Worn rings lose tension and that is a bigger reason for leaking than wide gaps. Years ago we rebuilt a Healy 3000 engine and it used oil but the numbers were good. Someone told the owner to take it for a good highway ride and not baby the motor. Oil usage problem fixed. Running the engine with a vacuum gauge might give you a better idea of what is going on. I think you can test individual valves by putting a shop vac to the associated port and then squirting some liquid around it to see if it leaks by.

[theHIGHLANDER]

Were the rings also "clocked" in proper sequence at the 1st build? They should all have their gaps on about 1/3 of each circumference, never close or all open to each other. I'm surprised how many don't know or skip that check. Just sayin...

[Ronnie]

Originally Posted by theHIGHLANDER

Were the rings also "clocked" in proper sequence at the 1st build? They should all have their gaps on about 1/3 of each circumference, never close or all open to each other. I'm surprised how many don't know or skip that check. Just sayin...

The rings rotate in the bore while running.If all the gaps were lined up when tear down occurred that would indicate s different problem.

R

[Dodge]

As a side note, back in the 70's the Cosworth engines that were used in formula one cars came with a manual that had a section on how to use Bon Ami to seat in rings in a cylinder that hadn't sealed. With individual fuel injection stacks you could do just one cylinder if you wanted.

[jake197000]

i wouldnt hone it without taking it apart.have i done it ya.but that was before i knew better.youve come this far.better to do it right.

[rotorwrench]

This thread is close to a year old!

[Ronnie]

Yup ain't that a fact

R