VIDEO: Consequences of extremely tight piston ring end gap clearances

[laserspeeddemon]

I had National Speed Inc, in NC do my build when I was deployed. It lasted 120 miles. I recently tore down the motor to try to diagnose the failure. A compression test showed 155, 155, 120, 100 psi. A leak down test showed that the piston rings were leaking.

Some context to the situation is that the National Speed got the car in February. They promised to have the car delivered in May, which prior to my two week break from Afghanistan. On my way back for my two week break I emailed and asked them if the car was ready and they said "No." We discussed it until I forwarded their email to them and they agreed that the car was past it's deadline. Two days later the car was being delivered to my home. My guess is that the rushed the build.

After pulling the head, this is what I got.

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It is my assumption that they failed to machine the rings in anyway. The end gap clearances ranged from 0.14"-0.17" on the top rings.

My question is what are the consequences of having a ring gap that is extremely tight?

 

[yhype]

The top piston ring is the compression ring so a tighter end gap clearance would cause higher compression numbers and higher cylinder pressures while running (would image it would destroy pistons from excessive pressure)....may be a problem to address while you have it apart but I would not think this is where your problem is. Was the engine broke in prior to it being delivered to you correctly? Have you checked bearings, valves/seats?

 

[95DsManiac]

Have you checked the valves for proper seal? Or check the guides for excess wiggle room?

For my build I did (did it myself when I worked at the machine shop) .022 top and .026 bottom and compression is 185 across.

Even if the rings aren't the problem, they still are "A" problem. There should be no way in a hell any machine shop that knows anything would let the engine leave the shop with different ring gaps. They should all be the same, if not minimum off by 1. I would deffifently check everything to do I high the engine.

Sorry for your situation bro, it sucks when other people mess up your things. If you have any questions please ask, I'll help as much as I can. I still have a piston ring gapper I can send to you if you can cover shipping. Let me know.

Anthony B.

God bless

 

[Mischif]

Pick a standard and stay with it. Your saying .22 but your using inches so its .022
Compression Ring end gap per the factory service manual is .0098 - .0177 INCHES. In metric that is .25mm - .45mm.
Maybe thats why your thinking your gaps are too tight, you seem to be mixing them up.

So your problem is two of your cylinders are gapped way too big, the other 2 are within spec. They definitely just threw your motor together. Theres no excuse for all your gaps to be all over the place.

On the bright side, at least they weren't gapped too tight. That can cause severe cylinder wall and piston damage.

 

[95DsManiac]

.017 is not too big, that is still tight. Even if the decimal is in the wrong spot you still get what he is saying. Either way, it is tight, please post factual information, being kind, we don't want him to mess up his motor.

 

[Mischif]

.017 is not too big, that is still tight. Even if the decimal is in the wrong spot you still get what he is saying. Either way, it is tight, please post factual information, being kind, we don't want him to mess up his motor.

So i guess the FSM isn't factual information? So why is it that his cylinders that have the highest compression numbers have a tighter gap then his cylinders with a bigger gap and crappy compression? Piston 1 and 2 with thier gaps of around .02" are too big.

 

[Fullthrottle7]

^ Correct when the parts inside the motor are no longer stock. Why would you assume that a cast piston expands the same as a forged high expansion piston, thus requiring the same ring gaps and PTW spec. I'm sure next you're going to tell him his PTW should not be bigger than .0025-.0030 right? The fact is that most high performance 4g63's on this site run end gaps above .020 on BOTH rings. Top is usually between .018-.024 and bottom is usually .020-.026 depending on goals. The compression numbers that he is getting is clearly due to a half ass build by an incompetent builder that rushed through the motor just to get the car back. While missing deadlines is crap to begin with, stuff happens. If you can't make a deadline for a reason then give it and concentrate while taking the proper time to finish the project well. If on the other hand they pushed it to the back of the shop since they had "plenty" of time to work on it like many shops do to work on other projects, then scrambled at the last minute and caused this, they should be footing the bill to make it right!

 

[95DsManiac]

^ your obviously not reading anything right if your saying he's correct. Read again, I'm not saying anything about his ring gaps but that there tight regardless. You work at a machine shop? You've built countless motors? And your forged piston comment, I said that already that he needs the same gap. And for ptw I wouldn't run anything less then .004, that's me though. Plus I race all my cars so I guess I have to run me loose anyways.

Regardless I'm not trying to get into a piss match, but please read my comments, I'm not going to give false information.

 

[laserspeeddemon]

Pick a standard and stay with it. Your saying .22 but your using inches so its .022
Compression Ring end gap per the factory service manual is .0098 - .0177 INCHES. In metric that is .25mm - .45mm.
Maybe thats why your thinking your gaps are too tight, you seem to be mixing them up.

So your problem is two of your cylinders are gapped way too big, the other 2 are within spec. They definitely just threw your motor together. Theres no excuse for all your gaps to be all over the place.

On the bright side, at least they weren't gapped too tight. That can cause severe cylinder wall and piston damage.

You are focusing on semantics. Really. In the video at the EXACT same time I state (1:37 in the video) the wrong numbers ("point two one"), I add a citation that states that "According to Total Seal, who makes the rings for Manley, they recommend 0.021" for the top and 0.028" for the bottom"

In addition, you can CLEARLY see at 2:17 on the feeler gauge that it's show 0.022" or 0.55mm.

My question is not whether you think the tolerance was or was not too tight, that question was already answered by Total Seal and the answer is that the gap was about 25% to tight; the question was what are the consequences of the extremely tight tolerances of ring gap. The second row rings were also in the 0.017". My assumptions is that the improper ring gap caused damage or warped the rings, which then caused the compression to drop. But I wanted confirmation.

 

[95DsManiac]

IMHO I don't think it is your rings, but something else, maybe valve seat to valve seal. If you can take out some valves and with just the valve slide it back in, with your other hand push it up and smack it back and forth for a few seconds (spraying graphite spray or simply cleaning before hand is key) and see if only can see a full ring around it. You could also put the valve 3/4 of e way back in the guid and see if there is out of the norm play side to side.

If you were babying the engine for the break in period, I don't think tight ring gaps is the problem. BTW, what was your break in period? How did you break it in?

What is your Piston To Wall clearances? (PTW)

To make things a million times easier as far as rings, do a leak down test, really though. It would save you time and less headaches. Trying to look for help on here can only go so far without tests being done on on our end.

God bless,

Anthony B.

 

[Mischif]

My assumptions is that the improper ring gap caused damage or warped the rings, which then caused the compression to drop. But I wanted confirmation.

TOO TIGHT of a ring gap will cause the rings to butt up against each other when they expand from heat. This will crack ring lands, shatter rings into pieces, and gouge your cylinder walls. Anyone of those or all of them could happen from gaps being too tight.

When you did the leak down test, did you get any air at all coming from the valves? Now that you have the head off have you poured water into the intake/exhuast ports to get an idea of how the valves are sealing?

I think a certain shop owes you a new rebuilt motor thats done right this time around or reimbursement of some kind.

 

[Fullthrottle7]

^ your obviously not reading anything right if your saying he's correct. Read again, I'm not saying anything about his ring gaps but that there tight regardless. You work at a machine shop? You've built countless motors? And your forged piston comment, I said that already that he needs the same gap. And for ptw I wouldn't run anything less then .004, that's me though. Plus I race all my cars so I guess I have to run me loose anyways.

Regardless I'm not trying to get into a piss match, but please read my comments, I'm not going to give false information.

Not sure how you thought I was referring to your post when I put an arrow to the guy above me and put all of the same exact specifications that you've been suggesting? He questioned your post "if the field manual is incorrect information" to which I replied yes! The field manual is definitely incorrect information in regards to aftermarket parts and refers only to the stock cast pistons. I don't need to read again because I gave the exact same suggestions that you are giving. I gave a range of ring gaps which you've confirmed are accurate as well as the absolute minimum PTW for a forged 2618 piston of .004" which you also confirmed, although that's still tight for a Wiseco or Ross slug. Don't get so defensive man we've all built motors you are definitely not the only one and I literally gave him the exact same advice you have. And yes, I have worked in a machine shop and have built countless motors, I run a 5 axis Zimmerman mill every day. Everyone is so eager to nitpick posts anymore and half the time they end up arguing over the same thing being said just worded differently then they might, damn!

 

[95DsManiac]

^ please excuse my misunderstanding! my apologies.

Hope the op figures this out.

 

[mercaholik]

Despite any misunderstandings, this thread has some good useful info. Just curious if you are gonna use new .20 2g piston and wanna push the limits should you run looser ptw and end gaps? Sorry no thread jack intended, but these guys have some valuable info for a lot of newbs that wouldn't even know to look for it.

 

[laserspeeddemon]

Well I moved and brought the car with me. I can not find any fault visually with the old rings. I also inspected the pistons. I cleaned them off using brake cleaner and a Magic Eraser. Came out really good. I re-honed the cylinders and I bought a new set of Manley rings. I have my own ring grinder and went to work.

I an running a 16g with about 23 psi to start with but my original plan was to be running a Holset HX-40 with Meth injection and some where around 35-40 psi which is why I needed a the larger gap. I had a HX40 running 25 psi and a Meth Kit. I went with .021" in top and .028" on the 2nd ring. The oil rails need to be gapped NO LESS than 0.015" Since the where already bigger than that, I didn't need to grind them at all.


But National Speed stole the Meth Kit and then when I sent the HX40 for them to fix (since it seized due to their own negligence) they stole that too.

 

[jimsgsx]

Thats why we have court and bring your documents to prove all of this. Time to take this to the appropriate lawyer.

 

[laserspeeddemon]

BTW, I just wanted to say that rings gapped on the NEW rings at around 0.014", so it is my suspicion that National Speed never gapped the rings at all.[DOUBLEPOST=1417469320][/DOUBLEPOST]

Thats why we have court and bring your documents to prove all of this. Time to take this to the appropriate lawyer.

I tried hiring a lawyer. They won't take a case unless they get like some ridiculous amount. And the money I had towards a lawyer went towards moving.

 

[911gdsmboostin]

Just a pointer coming from a machinest 1st it does seem like u got your self into a lower grade shop where quantity is sought after er then quality, 2nd the bores look like mirrors even with 500 miles if properly honed should look way better then that they look terrible but may be camera angle, 3rd u can't use a piston to square a ring in a block it will be close but not right most pistons are slightly domed they should be squared with a square my guess is your right and the machine work was pushed through and over looked to make a dead line in our shop we would ask for more time to do it right and if you spent 8000 and if failed we would make it right but I feel for you man and understand why people get discouraged with machine shops because it is places like that that will make good shops loose business over simple mistakes that they know should be done better always quality always clean our motors goes through 3 parts washers before assembly and every thing is inspected any sighn of dust or anything calls for being recleaned . also will add ring failure is uncommon unless they do a slopy job on the hone or not checking clearences in 30 years our shop only ever had 2 ring failures one was a customer improperly installing rings the other was unexplainable 6 rings broke out of a high HP v-8 and we took the hit we only asked he pay for new rings as we took care of all the machine work and assembly. Best regards and good luck on your build

 

[laserspeeddemon]

No, this shop came HIGHLY recommended and they do work on cars like Aston Martins. Or at least the claim they do. It could all be lies. The cylinders had the cross hatches visible, but the rings made vertical glaze marks...likely due to the improper ring gap, so I honed the block. Like you said, I'm sure they just rushed the assembly and forgot some minor details. And since their other clientele drive high end cars, they just swept me under the rug and hoped I would go away.

 

[911gdsmboostin]

Sounds about right... That's a shitty way to run a business sorry for your loss but I'd keep at em bout it or have they basicly told you to lb salt

 

[laserspeeddemon]

http://nationalspeedinc.com/
https://www.facebook.com/NationalSpeed

They have completely ignored all emails and phone calls and I don't have the money to sue them.