Cause for early ring failures on 4.625" bore?

[Robbie Racer]

I was wondering if anyone else out there is running a large bore size (4.625") blower motor (Merlin Pro tall deck block). I am having problems with early (20 hours) ring failure and would like to know if any one else has this problem. We refreshened the motor over the winter (because of excessive oil consumption last season) and had the block machined with piston oilers to try and pull more heat out of the pistons in order to get better ring life, but that didn't seem to help this problem. We put back in the same type of rings (Speed Pro, 1/16", 1/16", 3/16" oil rings and a Hell Fire top compression ring). It uses a 1/2 quart of oil every 1 hour of run time. Any thoughts if the cause of this problem is caused by excessive heat generation between the very thin cylinder walls? Or, should I be using a different type of ring?
Any thoughts are appreciated.

[Fiat48]

Was there any flaking of the moly on the rings you took out?
Are you sure the oil consumption is ring related (via leakdown test) or is it possibly guide clearance or seals?
Cylinder honing: 625 finish or plateau hone with 3 strokes of 800?
Not familiar with the oilers or the hellfire ring.

[Infomaniac]

What stroke and rod length are you running?

[Robbie Racer]

Thanks for the reply guys.
Fiat, I think I remember the builder telling me that there was some flaking of the moly when he took them apart the last time. I will be checking leak down numbers next week but expect it to be about the same as last season before we refreshened it, since the oil usage is the same. The numbers last year were: #1-18%, 2-14%, 3-8%, 4-32%, 5-24%, 6-16%, 7-16%, 8-24%. I do see some blue smoke only when I first start the motor. I will try to find out what honing procedure he used and report back here.
Info, I know the stroke is the same as the bore (4.625") but don't know the rod length. I will get back to you on that.
By the way, I think the pistons are gas ported. Is that a good idea for a long endurance blower motor application? Another thing to consider is that we only had minimal break in time on it on the dyno (with normal mineral oil) before we changed to synthetic and started numerous dyno pulls. Do you think this minimal amout of break in time might have something to do with this problem? Have you guys seen any other other blower motors with this large of a bore in an endurance (poker run) application that didn't use oil? I'm still wondering if the small amount of material between cylinders is allowing too much heat transfer between cyliniders which may be killing the rings.
Thanks again for the replies.

[Fiat48]

Possibly the speed pro rings are using a light tension oil ring. Check that out. They are available with std tension oil ring. Just something to check. Also...I suspect guides...the puff of blue on starting.

[Robbie Racer]

Fiat, I did ask him about the light tension rings and he said that was not the case as he used standard tension rings. He did say that he set the guides up a little loose for this application. Do you think that I could be losing that much oil out the guides? I guess when I check the leak down numbers next week and if they are as bad as last year, that will tell me that the oil rings are gone again.

[Fiat48]

Main thing on the guides is that were honed to size and straight and not broached to size. Broach not very good at making a nice round hole. I usually run .0015 intake and .002 exhaust guide clearance. No seals for drag stuff...but seals on the intakes for non drag stuff.
Tough part in my helping you is we change oil so often..no real clue to how much oil we burn. But even with those guide clearances we don't get any smoke.
Reason I mentioned light tension oil rings was I tried a set years back and got the puff of smoke dealio. So, I went back to standard tension. On the block thickness and cylinder wall flexing theory...I think those blocks are still pretty thick even at 4 5/8 bore.
Maybe Info has an idea about R/S ratio he was asking about.

[tbanzer]

I put together a 455 pontiac and the owner put in synthetic after I broke the cam in. Ran that motor for about 10000mi and it used oil at a rate of 1qt /500mi. Pulled the motor back down ball honed the cylinders, installed new rings and ran mineral oil for the first 1000 mi and now it uses no oil.

[058]

Keith, I think the gas ported pistons for an endurance engine is a bad idea. It loads the rings too much, especially with the blower. IMO that is why the moly is flaking off the rings. What do the cylinders look like, any scuffing? What about the ring lands? Any detectable wear or grooving?

[Robbie Racer]

Fiat, I hope you are right about the cylinder walls still being thick enough. I'm not very excited about the possibility of throwing this block away and buying an new one. :(
Bob, that makes sense to me on the gas ported pistons for this application. I do remember that there was some scuffing on either the pistons or the cylinders when we pulled it apart last winter. But I don't remember if there was any detectable wear or grooving in the ring lands. I will ask that question and get back to you on that.
Thanks guys.
Keith

[Infomaniac]

I am suspect of side loading with a combination like that. Did you find out rod length?

[INEEDAV]

What is the ideal ration of rod length to stroke?
I guess the longer the rod the better, but where does it become critical?

[058]

Originally posted by INEEDAV
What is the ideal ration of rod length to stroke?
I guess the longer the rod the better, but where does it become critical? There is no "ideal" r/s ratio. The ratio is determined by what the engine is to be used for. A short rod is primarly used for engines that operate in a narrow rpm range and uses the rapid accelleration rate of the piston to enhance cyl. filling on the intake cycle. A long rod engine is used where a broad torque curve is needed and operates over a wider rpm range. There are more arguements made in favor of a long rod engine because it has the wider torque curve, cam timing is more tolerant to the engine and the intake tract is less sensitive to tuning. There is alot more to what determines r/s ratio and this just scratches the surface of this age old debate.

[DogHouse]

I run 4.6" bore, 4.5" crank, 6.8" rod, and a 1.145" compression height piston. It's only naturally aspirated, but it uses oil and always has, much more than a more "normal" engine. It's not unusual for me to add 1-2 quarts after a long weekend of running hard. I think the short pistons are the culprit for two reasons, one being that they probably tend to rock a bit more than a taller piston, and two because the pins are way up into the oil ring lands. I just figure it's part of living with an engine that's a lot bigger than it was ever designed to be! It is a little strange that I never notice any blue smoke, seems to run pretty clean for the most part unless I've got the idle set too fat.

[cjordan]

I run 4.60 bore, 4.75" stroke, and either a 6.7" or 6.8" rod (can't remember). This is a NA motor and it doesn't use hardly any oil. I would guess a 1/2-3/4 quart every 10hrs.
One thing I found is that if I purposly run about a qt low (9qt) instead of 10qt it really reduces comsumption. Another words, the motor "consumes" alot until its down about a qt then doesn't use hardly any. So I just run 9qts with no problems.

[Robbie Racer]

Info, the rod length is 6.635". Do you still think that could be causing excessive side loading?
Fiat and 058, I was in error about the moly flaking. He says there was not any flaking of the moly but that the rings were just worn out. And that the pistons looked like they had seen a lot of heat.
Dog House, I also have a 580" blower motor with a 4.5" stroke x 4.560" bore (don't know the rod length) and it doesn't use a drop of oil. That's why I was suspecting the bigger bore as possibly allowing too much heat to transfer between cylinders. But maybe it has something to do with the longer stroke causing more side loading that is causing the ring failure problem.
cjordan, that is great that you have that long of a stroke and still don't use much oil. Does your block have a 10.200" like mine or do you have the really tall deck in order to use the longer rod length?
Thanks again for the feedback guys.
Keith

[don johnson]

For what it is worth I run 2 blown Teague 1050 HP, 572 CI Merlin motors that do not burn ANY oil. I run many poker runs every year and run the boat hard all season. This is my 2nd season on these motors and I doubt I go through more then 1/2 quart between oil changes every 35-40 hours.
Teague has been building my motors for years and the only thing I ever have to replace is roller lifters. I go through a set of lifters before I burn a quart of oil....
Good luck!

[DogHouse]

So it seems that some are running shortie pistons and still getting good oil control. Wonder why mine's using a bit. I don't see any evidence of burning it (smoke, oil fouled plugs, etc), and it's not dumping big amounts into the bilge, it just disappears. Maybe it's aliens. :confused:

[cjordan]

10.20" merlin II.

[Infomaniac]

Had to edit after calculating again. 1.43 rod/stroke ratio as copared to stock 454 1.53 ratio
You must be running a Merlin Super Block. That stuff will not fit in a normal tall deck 10.2 block.

[Robbie Racer]

Info, are you talking about my 4.625" stroke motor or cjordan's 4.750" stroke motor? I was under the impression that if you went with a 4.750" stoke, you would need to go with the Super tall deck block with the raised cam.

[Dave C]

RR,
I'm not the expert here but you can get a 6.7 or 6.8 rod in a 10.2 block (tall deck) with a 4.5 stroke but you need "special pistons" made that have the pin located higher in the piston.
I understand this makes some builders nervous. ;)
I was looking at a 572 combo like doghouse's Merlin with a 4.5 or 4.56 bore x 4.5 stroke.
Info told me he likes 4.6 x 4.25 (565). instead. Personal perference I think? But then again being a stickler for details makes for a good builder.
BTW, why did they do 4.62 x 4.62. Just curious? 620 cid!

[Robbie Racer]

Dave, it's a long story on why I went with the 4-5/8"x4-5/8" (621.7") combination. Originally I had planned to build a 4.5x4.5, 572 but my first motor builder out of lake Havasu said that he needed to bore it to 4.600" in order to use the (used) heads that I gave him. We found out a year or so later that the first builder had screwed up on one cylinder and gouged the cylinder wall when pulling the bore tool out. So, we had to bore it out to 4.625" to clean that up. We also found out that the used 4.5 crank that I had given the first builder, had a crack in it. So we decided since I had to buy a new crank and pistons anyway, we should go with a longer stroke crank since they are about the same price. My current motor builder told me that I could go up to 4-5/8" in the stroke and still keep a decent rod ratio. I think that with the 4-5/8" crank, he could only get a max. rod length of 6.6" to fit. I now wish that I had stayed with a 4.5" stroke crank because it would have probably caused less side loading on the pistons which may be contributing to my early ring failure problem. Based upon the piston and ring reliability in my 4.5" stroke x 4.56" bore (580") motor, I would use that combination again without hesitation. The jury is still out on if I would ever build a 4-5/8" stroke motor again. I think maybe a better idea would be to go to a Super Tall deck motor and build a 632" deal the next time.

[cstraub]

I would have to favor side loading also on the rings. With that arm you have and a CD of around 1.290" and I would assume a stock pin diameter of .990", the pivot point is just wearing the rings out in the the applications. Fine for a race engine that will get freshened, but not for something that needs to run 400 hours before tear down.
Chris

[cjordan]

4.75" crank will go in a std. 10.2" block. I do have custom JE pistons with the raised pins. The skirts are short and the pin actually extends into the ring grove. The only thing I am not 100% on is the rod length, but I am pretty sure it is a 6.7" rod.
638" CI is max recc. for a 10.2 block 4.75 stroke / 4.625 bore

[Robbie Racer]

Chris, thanks for the feedback. Any ideas on how cjordan gets away with more stroke than I do and he doesn't use any significant amount of oil?

[cstraub]

Robbie,
I would assume he is running a Super block. If so his compression distance is much greater locating the pin below the ring pack.
Chris

[cjordan]

Chris; It's a std 10.20 Merlin II block. We thought about a raised cam block but decided against it. I just confirmed with my builder that my rod length is 6.70".
Robbie; I'm no expert on ring gaps. But mine are relatively tight and can be tighter due to NA vs blown. Mine are .021" and .023". Those are a little tighter than I would prefer (builder set them there), but have created no problems in over 65hrs of use.

[cstraub]

Cjordon,
You have a 1.13 CH. Who is the engine builder? I may know him. I am an X cumberland rat from Louisville.
Robbie, have you got full skirt pistons or T's?
Chris

[cjordan]

Hawkins Racing Engines, Richmond IN. Jim Ray is the owner. Primarily builds drag racing and circle track motors.

[Robbie Racer]

Chris, here is a side view pic of the piston.
Would you call that a full skirt or a T?

[cstraub]

Full skirt. Looks like a tapered pin. Alll good stuff. What oil pan do you run on this old girl? Sump depth? Kick out?
Chris

[Robbie Racer]

Chris, we run one of your 18 quart pans with a kick out. (See pic). I don't remember the sump depth though.
Keith

[cstraub]

Robbie,
I sent the pic to our Offshore guy. I'll get back to you.
Chris

[cstraub]

Keith,
Unless you specified an 18qt pan, we don't don make one. All of our stuff is 12 to 14 qt. Pull 6 qts out of the engine and run it and see what happens.'
True Story:
Had a customer that mistakingly filled one of our offshore pans with 24qts of oil. This was a twin engine application. The bullet with the correct oil was dynoed first by chance. The second was dynoed, with the overfill, and she was 100HP shy of the twin. He took it off the dyno and started to drain the oil for tear down. After filling a 5 gallon bucket, he knew what had happened. Put 12 qts back in, set it on the dyno, with in 4 HP.
Chris

[Dave C]

cstraub... question?
1.29 CD ratio?
1.13 CH ratio?
que?
thanks
Davec<---- tried multiplying/dividing variables before asking. sorry!

[Robbie Racer]

Chris, I'm pretty sure the builder had you build a custom pan with as much of a kick out as would fit in the boat. I will check for sure the next time I talk with him.
Question: Will lateral gas porting of the pistons affect leak down numbers? I just got the leak down numbers as the motor is currently: The worst cylinder is #5 at 30% with #6 being 28%. The best cylinder is 17% and most of the rest are in the 20 to 23% range. I wish that I had it leaked down right after it was refreshened for reference but we never got around to doing that.
Thanks again for all the feedback.
Keith

[cstraub]

Keith,
Stan hasn't looked at the pan yet. Can you give builders name and date of build time and we can pull the print.
Dave,
I may have goofed. Let me figure this:
4.750 / 2 = 2.37 rounded
Rod length 6.600
Deck 10.20
1.230" Okay, I did goof. Thats not as bad.
Chris

[Robbie Racer]

Chris, the builder is DNE Motorsports Development in Costa Mesa, CA. I would guess that the pan was ordered around Feb or March of '03 since we went to the dyno in April of '03 for the first time. I think Dave orders a lot of pans from Stef's so it may be hard to pin down which one this is.
Regarding your earlier question about oil level. The first year we didn't have a dip stick installed so I couldn't keep an eye on the oil level. I first noticed the usage problem when my low oil pressure alarm went off upon fairly hard deacceleration from a 120 mph pass. It had gotten low enough to unload the oil pump as all the oil that was left in the pan rushed forward. When we drained the oil it only had about 8 or 10 quarts left in it if I remember correctly. Now that I have the dipstick installed, I can keep an eye on it. It will keep dropping down until it gets off the end of the dip stick and then it takes about 4 quarts to bring it back to the full mark.
This much we do know for sure. The rings were toasted when we pulled it apart over the winter and based upon the above leak down numbers, I suspect they are toasted again (in only 30 hours on the latest refreshening). The question that I still have is what is causing the early ring failure. The rest of the motor looked perfect when we pulled it apart. Based upon the earlier feed back on this thread it looks like the most likely causes could be:
1) too much side loading of the piston in the cylinder due to less than ideal rod ratio.
2) maybe the lateral gas porting of the pistons?
3) 4.625" bore size??? Nobody else that has replied to this thread has any experience with a bore this large, so we still don't know if that might be contributing to this problem.
Any disagreements or other ideas on what else might be the cause of the ring failures?
Thanks again,
Keith

[cstraub]

Robbie,
Stan said to tell you that you had one hell of an engine builder in Dave. The pan capacity of that is no more then 14qts. Dave may have have calculated the entire system at 18 qts. Stan remembered your engine because it has the Titian pump correct? Also Stan said we leave the dipstick long on those pans so that after the engine is rigged with oil lines then the builder can cut and mark the stick.
Chris

[Robbie Racer]

Chris, the next time I talk to Dave I will try to clear up my confusion over the 14 qt. vs. 18 qt. pans. I have one of your 14 qt. pans on my 580" Larry Peto motor and I thought it was slightly physically smaller than this pan but I may be wrong.
I don't remember what the name of the oil pump manufacturer was but I do remember Dave taking great care in that area. Here is a picture with the oil pump mounted on the motor. Can you tell if it's a Titan pump from the picture?
Keith

[cstraub]

Sure is. Stan pulled the print on the pan because Dave's stuff is usually custom. We are for sure it is MAX 14qt capacity.
Chris

[Robbie Racer]

Chris, thanks for asking Stan to pull the print. I left a voice mail and an email for Dave to refresh my memory on what he told me the capacity was at the time. Hopefully, he will get back to me when he gets the time. I know that over filling a motor with oil can cause a loss of horsepower but can it possibly cause the oil rings to fail? If so, then this could be a simple answer to my oil consumption problem (and way cheaper to fix than some of the other solutions that we are looking at). :D
I just looked up the bill of materials that Dave gave me and it says it's a Stef's #2943 pan. What does that part number tell you?
Keith

[cstraub]

14qt Merlin Offshore Pan, pickup kit.
Chris

[Dave C]

sorry I mean I don't understand the ratio in the first place?
I can't correct you if I don't know what I'm doing. ;)
Originally posted by cstraub69
Dave,
I may have goofed. Let me figure this:
4.750 / 2 = 2.37 rounded
Rod length 6.600
Deck 10.20
1.230" Okay, I did goof. Thats not as bad.
Chris

[cstraub]

Compression height. . .pin location. When locating the pin up in the ring pack, it can lead to excessive side thrust loading of the rings and cause wear. Fine for engines that see regular tear downs but for long haul stuff not the best set up.
Chris

[Robbie Racer]

One of the Offshore Only members gave me the number of a tech guy to call at Competition Products (they sell pistons and other performance motor products). I talked to Roger the tech guy and according to him the 6.635" long rod in a 10.200" tall deck block gives a better rod angle ratio that stock. Chris can you verify this? Maybe Roger didn't hear me when I said I had a 4.625" stroke. Roger thinks that the gas porting is causing the early ring failure and shouldn't be used on a long haul type motor.
Thanks,
Keith

[cstraub]

Have you talked to Dave about capacity yet?
chris

[Robbie Racer]

Hi Chris, I talked to Dave this morning and he said that it took 18 quarts to reach just below the bottom of the screen in the pan. He suggested the next time we do an oil change to fill the filter (large Wix Racing filter) and then put 15 quarts in the pan, run the motor for a few minutes, then allow it to set for a few minutes, then mark the dipstick as that being full. Since we just changed the oil and filter and added 18 quarts (total including in the filter), it will be another 15 hours or so before I do another oil change. In the mean time, I think I will use the low oil level mark as my full mark and add oil again when it reaches the bottom of the dip stick.
Thanks,
Keith

[HBjet]

Interesting thread. I just want to say that I have a 12qt pan and I've seen RR's pan at DNE and that mother is huge. Way bigger then just 2qts over my Dan Olsen pan.
HBjet

[cstraub]

HB,
If our engineer says its 14qt, then it is 14qt. The founder of our company was Moroso and Hamburgers pan engineer and designer. I trust Joe when it comes to capacity. This is the same pan that Sterling, Crocket, Chief, Zuel, Kirks, and Eickert use. Most don't understand the windage that is created in an oil pan. Our design compensates for that.
chris