Ring gaps, keying and bearings

Can someone help me quell my OCD over ring gaps? I'm getting 87.75 Manley's and was thinking to do .020 top and .024 bottom like JT. Then Sho says these engines like .03 between rings and that .027 is way to large and will burn oil. Then CP recommends .04 between rings. I understand you need some space in between to prevent flutter. HP goal is around 500-600 with returnless PI. I want to see how it goes since it's so simple then maybe do return pi. I also want to build the engine once so it can handle 700 where the stock sleeves become the weak link. There's an MS6 making 800whp with stock sleeves.

Crank bearings also worry me. I'll be using Clevite AL MS-2245A. JT pushes big power on them which boggles my mind since bi-metal bearings are meant for oem level +50% above power. I heard somewhere tho some bearing manufacturers like to underrate their bearings so they can sell other ones. SP63 also does this: "In order to get extra oil to the rod bearings, we create a teardrop shaped cavity to the crankshaft's main oiling holes". I heard good things about King PMAX black and clevite H mains are impossible to find now. This will be a DD. I have clevite H rods.

At what point should you worry about crank Keying? Or is it not necessary at all? The ARP crank bolt has a tq spec at 140ft lb and another member found that the oem TTY is at 280ft lb. Seems like the ARP is too low.

 

First off I would like to say that engine failures we hear about on these platforms are typically diagnosed by "Amateur enthusiasts". This means that there is normally a lack of professional root cause analysis. This is why you hear some people make big numbers and run, while others have engine failure on stock power. This is especially true about "Keying" your crank. There is no clear evidence on this requirement. And I am personally willing to bet that keying was proposed as a preventive measure to poor engine assembly.

Ring end gap is chosen to compensate for expansion. IF the end gap is too tight, your rings could expand enough to butt up against each other and ruin your engine. IF the end gap is too loose, you could have oil consumption or compression losses, especially when cold. The reason manufacturers recommend a larger end gap is likely due to liability concerns.

There is a great explanation on this from HPA:

I also do not recommend big power numbers for a daily driver, as you lose a lot of daily driver comforts with big power numbers.

Finally bearings aren't expensive relative to the goals you have in mind, why not just buy the best on the market and go with that?

 

Thanks. This video is about installing rings not what ring gap to run.
From what I gather:
Sho "
sub 400whp, 0.019 top 0.022 2nd
550+ whp 0.020 top ring and 0.022 2nd ring at 36psi no oil burning till 85k
700+whp 0.021 top ring and 0.024 2nd ring, Chris' Garage 21mm top and 24mm 2nd ring gap
JT .020 .024, 38psi 650whp?

Seems like the safe bet will be .021 and .024. What messes with my head is CP Carillo recommends .04 between rings. But u guys are running .03.

I just noticed it says .004" bigger than top ring. I could be understanding it wrong.
There was a saying build it loose and get blowby, build it tight and get a large paperweight something like that lol. I would like to build it loose enough but not burn oil. I know you don't want the rings to touch.

Power and DD:
My view is this: make as much power as you can then turn it down for the street. Run full boost at the track when you have slicks on. While on the street run less boost through your boost controller.

Bearings:
Price wasn't the issue as they're all about the same. I'm just trying to find out what to run. Everyone tells me to run Clevite. That's another thing, ppl always say run "x" but then don't specifiy which AL or tri metal? King, Clevite, ACL pretty much all have bi metal or tri metal but ppl always say "Oh I run ACL's". Ok which? ACL aluglide, duraglide,race? I also heard Race are not good for DD as they're meant only for things like constant high rpm use like oval track racing.

Keying:
Sloazz6 with the 800whp ms6 runs a keyed crank https://www.youtube.com/c/Sloazz6/videos
JT doesn't at 650 but now has a timing gear problem or something
Still unsure about ARP's tq spec of 140.
Mabye I won't key it. It's just not a clear cut answer. SP63 recommends keying after 500whp where they say the crank can slip. But this could be advertising talk. Overspeed rates his engine stage 1 with no keying at 600whp .

 

DO NOT torque it to 140lb-ft. Use the factory spec, it's closer to 350lb-ft. I did that testing over 9 years ago LOL.

 

Would you happen to have a link? That number is blowing my mind. No risk of stripping the threads?

 

That place no longer exists.

Original data set is attached. My torque wrench only went to 250lb-ft, so I projected beyond that. You would believe it if you've ever tightened one to OEM spec. They're goddamn tight.

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So I should torque it to 90 degrees? Would one of these be needed?

I saw one guy do it by marking the bolt with a right angle mark then torqueing it down till the red mark reached the 90.
My Harborfreight 1/2 tq wrench only goes up to 150 I believe.

 

Do it however you feel comfortable measuring the rotation. I like marking it with a paint pen.

 

Thanks homie. I was just unsure cause the ARP will not stretch like the oem and was thinking the oem stretching would relieve some strain on the crank threads. Since the ARP doesn't stretch it transfers the tq directly to the crank threads. But I guess its fine.

Bearings: oddball Kevin also recommends bimetal mains.
https://www.youtube.com/user/hockeynube11/videos
I think I'm just gonna just send it with what I have. From what I learned any bearing contact on aluminum bearings will be catastrophic. Which is why you use tri metal which has a sacrificial babbit. But JT is making 650 no problems that's probably the max I'll go anyways. (in the foreseeable future heheh).

 

Not true. The ARP bolt will stretch just as far as the OEM bolt, but the ARP might stay in its elastic range (I never tested one to know). The OEM bolt only yields .001-.002", which is just barely getting into plastic deformation (~.15% stretch). Said another way, they'll have nearly identical clamp load when you torque them with the OEM method. The difference will be negligible.

Remember that all carbon steel has essentially the same modulus of elasticity

 

Others know much more than me, but I can say from my own limited experience that the the factory method is ridiculously tight. I‘ve done it with the engine in the car (on jacks) and I had to use my legs with a 2’ breaker bar and my back pressed up against something solid to get the bolt turned Out of the car it’s easier to get better leverage.

 

Is this in reference to the main studs? Are you saying that the torque specification provided by ARP is insufficient for the mains on this car?

 

Crank bolt. Yes, ARP's spec is shit. It will not provide sufficient clamping force.

Use a new bolt, use new crank gears, use new friction washers, torque to OEM spec.

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Someone told me I could reuse the crank gears. Do they actually go bad? I got everything else new oem.
For the ARP crank bolt I thought the point of using it over the OEM was that it's reusable? I read somewhere that since ARP's use lube their tq readings will be different than bolts that are dry like the OEM.

 

Lube....yeah I tested that too. In the attached pic, "UT" stands for "Ultra Torque", ARP's own brand of thread lube. The oem spec is torque to 75lb-ft, then 90°, so it really only applies to that initial 75lbft. It does make the 90° portion easier on your back, but it doesn't change how much the bolt stretches with that 90° rotation.

At 75lbft (from a baseline of 25lbft), ARP's lube netted an additional 4° of rotation.

At 90° of rotation beyond that 75lbft, it took approximately 80lbft les torque to achieve that rotation. It definitely works, but irrelevant since it's torque-to-angle.

Whether or not you use lube, you need to use the OEM procedure.


[At that time, I had just had my torque wrench calibrated for the engine build I was getting into. Just a fun fact.]








Don't chance it, get new gears. They do get a depression where the friction washers sit in some cases, causing a loss in pressure to the friction washer (more susceptible to slipping). This was the entire reason we talked about this stuff way back when and why I tested the crank bolts.




The ARP might be reusable, I've never seen anyone measure one before and after. Unless you do a before and after measurement of its length, it's not reusable IMO.

 

I thought a TTY was calculated so that it reaches the right amount of stretch to create the strongest clamp. So how could that apply to the ARP bolt which I'm betting has different qualities. It doesn't make sense to me. Or is also designed to be a TTY? I don't think it is because they specified a torque and not a degree. "The ARP bolt will stretch just as far as the OEM bolt, but the ARP might stay in its elastic range (I never tested one to know)."

For example: https://www.mazdaspeeds.org/index.php?threads/my-view-on-head-studs-for-the-mzr.3346/
UTS Values
-OEM Bolts- 150ksi
-ARP2000- 200ksi
-H11/L19- 240-260ksi

I thought I read somewhere ARP crank bolt is 8740 which is lower than ARP 2000 but I can't find that reference anymore.
https://arp-bolts.com/kits/arpkit-detail.php?RecordID=1659
Man I could've just used the oem bolt and made this simple.

So rotating the ARP with UT lube to 90 only gives 280 ft lb approx. The oem is 360 ft lb. Wouldn't that mean the ARP with lube has less clamping force? 280 vs 360. Or is the torque something you don't look at? Wait I just noticed your whole table is for the oem bolt with and without lube.


Summit racing: "TTY fasteners have an elastic quality. They are designed to stretch to a specific “yield zone.” When the fastener is torqued properly, it acts like a spring to apply consistent clamping force. However, the stretch is permanent. After they are torqued, they will never go back to the way they were."

I mean in the end if this is what works then I'll just do as you say. ARP with 75ft lb then 90 with UT lube. How do you feel about keying?

 

It's not TTY, it's TTA.

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ah so all that matters is the angle. interesting. That still confuses me about TTY bolts but ok

 

The numbers you have here are ultimate tensile strength (UTS). Don't confuse that with young's modulus (aka modulus of elasticity), which is the "spring rate" of a material. All carbon steels (which is every bolt type you've listed) have the same spring modulus when in the elastic range.

The OEM bolt just barely gets into the plastic range, so I would calculate it as if it was completely elastic just to simplify. If you do that, then the same procedure will net you the same results with any carbon steel bolt.

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So are you basically saying every carbon steel bolt will get into the plastic range at the same time if using the degree method?

Seems to me TTY means torquing the bolt enough to reach the plastic region. What is new to me is you're saying every bolt including oem,arp, other carbon steels all reach this plastic region at the same tq. The difference is when it will break (UTS). Then the ARP is not reusable because once a bolt is stretched it cannot be reused.






"All carbon steels (which is every bolt type you've listed) have the same spring modulus when in the elastic range." Ok maybe I'm wrong. You said when it reaches the elastic range, each bolt could reach it differently but have the same spring property when it does reach it. Then the difference would be how long it can stay in that spring range without breaking.