4.620 piston rings?

[peachesracing]

looking at a tall deck bowtie block thats bored 4.620. Having trouble finding a ring for that bore size. Would it work to use a 4.625+.005 and file it to fit? Would the oil ring tension be to high? Im looking to be fairly low tension. Or would it be better to use a 4.610+.005 and run with what the gap is?

[FC-Pilot]

I have run that bore size twice before. First I called Akerley and Childs and they sent me a set for my application and the second I called Total Seal and they sent me a set for my application. No problems either time. I don't know if they were "packaged" for a different bore or not, but I ran what they sent me and never had an issue. Picking up the phone in a situation like this is worth a mint. The guys on the other end are a wealth of knowledge. Just be sure to call them direct and don't call jegs or summit please. LOL

Paul

[pdq67]

But you didn't answer his questions and I have often wondered about his questions also.

Run a file-fit slightly larger dia. ring that will fit tighter or a slightly smaller ring dia. and don't worry about the slightly wider gap?

pdq67

[41apache]

I have ran the 4,625+5 in a 4.620 bore in a boat worked fine. it was a moly .043

[engineguyBill]

In a situation such as this, it is better to use the slightly larger ring and file-fit to size. The ring will have slightly more tension than it was designed for, but as long as the ring diameter and bore diameter are within .010", or so all is well. The smaller ring in larger bore will have far less tension than it was designed for and this may cause problems with ring seal.

[FC-Pilot]

But you didn't answer his questions and I have often wondered about his questions also.

Run a file-fit slightly larger dia. ring that will fit tighter or a slightly smaller ring dia. and don't worry about the slightly wider gap?

pdq67

My point was this, I called and specified my bore and what I needed. I got exactly what I asked for. Isn't that exactly what we want from our parts manufacturers?

Paul

[gruntguru]

In a situation such as this, it is better to use the slightly larger ring and file-fit to size. The ring will have slightly more tension than it was designed for, but as long as the ring diameter and bore diameter are within .010", or so all is well. The smaller ring in larger bore will have far less tension than it was designed for and this may cause problems with ring seal.

I agree that the larger ring correctly gapped is a better choice than a -0.005" undersize ring with potentially 0.016" too much gap or more. I disagree that the tension will be dramatically different. Fitted tension varies in direct proportion to the difference between free gap and fitted gap. That number (difference) will only change by 0.016 when fitting to a 0.005" larger bore. With a free gap of at least 0.500", that 0.016" change only represents a tension loss of about 3%

[peejay]

In a situation such as this, it is better to use the slightly larger ring and file-fit to size. The ring will have slightly more tension than it was designed for, but as long as the ring diameter and bore diameter are within .010", or so all is well. The smaller ring in larger bore will have far less tension than it was designed for and this may cause problems with ring seal.

I agree that the larger ring correctly gapped is a better choice than a -0.005" undersize ring with potentially 0.016" too much gap or more. I disagree that the tension will be dramatically different. Fitted tension varies in direct proportion to the difference between free gap and fitted gap. That number (difference) will only change by 0.016 when fitting to a 0.005" larger bore. With a free gap of at least 0.500", that 0.016" change only represents a tension loss of about 3%

I've installed brand new rings that were over .016" over spec for gap (not .016, but .016 over) and the difference in compression and blowby was negligible.

Sometimes good enough really is good enough.

[engineguyBill]

Free gap is the ring dimension that determines the amount of tension that the ring will have when installed into the target cylinder diameter. This tension is determined by the ring engineer and cannot be changed. Gapping the rings won't change the tension that is designed into the ring.

As I mentioned in my post it is better to use the larger diameter ring and gap it as necessary for the engine's cylinder diameter, rather than using the smaller ring in the larger cylinder diameter. The larger ring will have slightly more tension than it was designed for, which is better than the ring having insufficient tension.

I agree with the previous post, a gap set at the cylinder diameter (called gage diameter) that is .016" larger than the recommended gap will not necessarily result in loss of performance, nor increased blowby - in most cases. It is still a good idea to gap the second ring slightly larger than the top ring, however.

[ProPower engines]

looking at a tall deck bowtie block thats bored 4.620. Having trouble finding a ring for that bore size. Would it work to use a 4.625+.005 and file it to fit? Would the oil ring tension be to high? Im looking to be fairly low tension. Or would it be better to use a 4.610+.005 and run with what the gap is?

You have not mentioned what ring thickness you require to start with and that said that alone will have a bearing on ring tension. the difference between an .043 and a 5/64 ring is dramatic.
the other issue is are the pistons gas ported in some way?? Either vertically or laterally will allow the use of a lower tension ring and depending on top ring material and 2nd ring design for oil control ( I prefer a napier style 2nd ring ) and a reduced tension oil ring..
As for having trouble finding a ring set I believe you may be over thinking the issue at hand. There is several ring suppliers that can help with your ring selection design to best suit your needs. Also the bore finish is also critical for best sealing and longevity of the rings themselves and that is often over looked. Too rough of finish and you tear up the 2nd ring causing oil consumption issues as well as tearing the moly inlay from the top ring amgain sealing issues are the result there.

Call mike Jones at Total Seal and discuss your build needs with him and look at what is available from Total Seal as well as talking with the guys at Akerly and Childs about ring type and material choices.
And if you have pistons already consider gas porting them for the benefit of better sealing the top ring Or if you don't have pistons yet then lateral gas ports and ring thickness options need to be thought about.

As mentioned the 2nd ring needs to be a bunch wider then the top and if you want low tension oil rings for the build have you considered a vacuum pump?? If you are not running a dry sump oil system that will be the best way to get them to work properly otherwise a med low tension oil ring can be had from some suppliers.

Just saying you are better off making the phone call then e mailing places to get the info you are looking for as so much detail can be missed cause guys just hate typing anymore then they have to

[pdq67]

Thanks everybody!

Good info here.

pdq67

[engineguyBill]

Contacts:

Keith jones at Total Seal Piston Rings 623.587.7400

Roger McMartin at Akerly & Childs 661.702.1909

[peachesracing]

Thank you for all the replies I sure appreciate it. I'm not sure i'm going to purchase the block after looking at it. I'm leaning more towards a dart or merlin block.

[FC-Pilot]

Thank you for all the replies I sure appreciate it. I'm not sure i'm going to purchase the block after looking at it. I'm leaning more towards a dart or merlin block.

I have run multiple bowtie blocks out that far. Sonic check it, and if it checks out OK then I say go with it. What would the application be?

Paul

[peachesracing]

Thank you for all the replies I sure appreciate it. I'm not sure i'm going to purchase the block after looking at it. I'm leaning more towards a dart or merlin block.

I have run multiple bowtie blocks out that far. Sonic check it, and if it checks out OK then I say go with it. What would the application be?

Paul

its going in a mud truck. it wasn't the bore size that bothers me so much. It has damage to the bottom of a couple cylinders from a broken rod i'd say.