How important is the piston ring gap in an engine?
One key to a successful engine build is paying attention to the details. Performance engine builders know that if you sweat the little things, the engine will make good power, be responsive to tuning, and generally deliver on its end of the bargain. One place where these small things can pay off is with the piston-ring gap.
Does the piston ring have to fit the bore?
The ring has to fit both the piston and bore- correctly. There's no "oversize" ring for a standard piston or bore. There are 'file to fit' rings, these are made to have the end gaps hand finished for a more precise control over the end gaps. But the ring diameter would still be standard, or whatever oversize the bore is.
Should I buy an oversize piston for my engine?
Oversize rings also require the use of the oversize piston. Don’t order anything until you have taken the head off the engine and measured the cylinder properly. You may find that it is too worn to spend money on. You need to know the size of the cylinder now and if it needs to be glaze honed or bored before buying parts.
What happens when you oversize the piston rings?
I'd expect a bore worn bad enough that an oversize ring was being considered to have a pretty big ridge at the top of the cylinder. If new rings are installed, the ring's sharp, unworn leading edge will hit the ridge, often breaking the piston or ring.
How do I know if I need oversized piston rings?
Ring gap of more than . 008″ per inch of cylinder bore indicates an oversize cylinder and oversize rings may want to be considered.
When should you Rebore a cylinder?
Reboring is necessary when the cylinder wall is damaged, either due to wear and tear or excessive use. Some common signs that indicate you need a rebore include: Damage to the wall is too severe for honing to resolve, such as deep scratches. The cylinder is no longer round, which is often the result of overheating.
Does boring out an engine increase horsepower?
Boring an engine involves using machines to widen and taper the cylinders. From a performance standpoint, boring an engine could give you more horsepower and torque, as it will change the engine's displacement.
Is cylinder honing necessary?
More often than not, you will need to hone your cylinder when replacing the piston rings. That is because honing creates small crosshatches in the surface of the cylinder, to allow the wall of the component to retain oil and provide lubrication for the piston ring.
Do oversize pistons give more power?
The short answer is that a bigger bore is generally the best way to get more power. It creates more space, allowing for bigger valve openings, which in turn can bring more fuel and air into the cylinder.
When you bore an engine do you need new pistons?
If you over bore the cylinder, you must use a new piston. When clearances of the piston to wall are measured in the thousandths of an inch (or sub-millimeter) and you bore the cylinder +. 010" over (or +. 030" or whatever), there is too much gap for the old piston to take up the slack.
Do I need oversized pistons?
Always, always, ALWAYS consider oversize pistons, even on a low mileage engine block. Do not immediately assume your engine needs standard bore pistons. With the large assortment of pistons on the market, the selection of off-shelf pistons is huge and no longer costs tons of money for non-standard pistons.
What is the best bore to stroke ratio?
Rod Ratio: The Math We hear a lot of engine builders shoot for a ratio between 1.5:1 and 1.8:1 on a street motor, with 1.75:1 considered ideal, regardless of application. The most highly developed four-stroke engines in the world - Formula 1 and motorcycle engines - have rod ratios of more than 2:1.
What is a stroked out engine?
0:004:32Stroker Engines Explained - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe stroke relates to how far the piston can be pushed down in turning the crankshaft. It alsoMoreThe stroke relates to how far the piston can be pushed down in turning the crankshaft. It also defines displacement.
How long should you hone a cylinder?
You should only have to hone for about 10 to 15 seconds at a time until you can see consistent crosshatch marks. The ball hone will be a little bit more abrasive, which is why we don't recommend using a ball hone on plated cylinders unless they are specified to be safe.
What is the best lubricant to use when honing a cylinder?
For best results whenever you hone, Brush Research Manufacturing (BRM) recommends using Flex-Hone® oil.
What grit Flex-Hone should I use?
Hones with 180 to 240 grits are good choices for general deglazing where the cylinder is not going to be bored or honed. A 320 grit, and even sometimes as fine as 400 grit are often used in high performance applications with high performance ring sets.
Why do you have to set the gap at the bottom of the bore?
You have to set the gap at the bottom of the bore (the least worn part), because the gap is tightest there.
Why do cylinders get bored?
Typically every cylinder is bored because it incresases displacement, and possibly piston weight. Not always. It was not uncommon in the old days to fix one cylinder by overboring. A one-cylinder fix today usually involves sleeving the really bad cylinder to match the good ones.
What is a 010 piston?
The .010, 020, etc are overbore sizes for the pistons, they are that much larger diameter than a standard piston. To accommodate a larger piston a larger ring is required. So if the piston is .010 larger, the associated ring for it must be equally larger. There are exceptions to the rules but usually all cylinders are overbored by the same amount.
What is a file fit ring?
These are called "File-Fit" rings. They are made just a little too long and you file the ends to get the ring gap where you want it. They can be used in new engines when trying to get the ring gaps absolutely perfect (for racing, etc.). In old engines they can be used to make the wear situation a little less bad.
How important is the piston gap?
One key to a successful engine build is paying attention to the details. Performance engine builders know that if you sweat the little things, the engine will make good power, be responsive to tuning, and generally deliver on its end of the bargain.
Which piston positions the top ring farther down from the deck?
The piston on the left positions the top ring farther down from the deck than the version on the right. Supercharged and turbocharged engines tend to do this to protect the rings from excessive heat. Normally aspirated drag engines will move the ring closer to the top. This position affects end-gap specs.
What to do after cutting a cylinder?
After each cut, always dress all four edges of the trimmed side with a whetstone. This will prevent damage to the cylinder wall and also the piston, when the ring is installed. It’s also a good idea to chamfer the opposite side as it’s not uncommon to find sharp edges there as well.
Why do gap specs differ?
As heat is applied to a metal – like a piston ring – it will expand. Because the ring is contained in the cylinder, the initial cold gap will close as heat is applied.
Why is aluminum tighter than iron?
This is because the block will expand more than its iron counterpart.
Why does a cylinder have a cold gap?
Because the ring is contained in the cylinder, the initial cold gap will close as heat is applied . If enough heat is present, the ends of the ring could even touch. As soon as that happens, the ring can no longer accommodate further expansion and begins to tighten in the bore.
Why is there a gap at the end of a ring?
It stands to reason that a large gap at the end of the ring makes for an easier leak path. This can directly bleed off the precious cylinder pressure that is so difficult to achieve. The ideal situation sees this gap held to an absolute minimum. This is where we apply the art of filing ring gaps.
ziggo0 Proven Member
I wasn't originally going to be doing a mini rebuild but I figure while the engine is apart, re-ring it. I have a brand new set of rings for std size bore pistons, but the pistons in my engine are 1mm/0.040 over.
tkelly27 Proven Member
Well, try it. If you're trying to run a big gap and the ring manufacturer made them tight from the factory you may be able to get away with it. I wouldn't plan on it. You could probably do the math and see what kind of gap it's going to give you, I'm not about to do it for you though.
ziggo0 Proven Member
As I stated I have no problem paying for the correct sized rings...I figured I would simply ask just in-case they could be used...no harm in asking a simple question....
BogusSVO Proven Member
keep this in mind too.... for every .001 you open the bore you gain Pi (3.141) on your ring gap so with a .040 over bore X 3.141 = .12564 plus what the "built in ring gap" is so you would be appox .145 ring gap.... I would say thats a bit much...