Forged Redeye Engine Failure :( Why????

[Bobo]

Are you pointing out that it failed because of a lack of chamfer on bolt holes? I see no witness marks from the stud and washer on that bolt hole.

 

[16GoManGoHC2]

Are you pointing out that it failed because of a lack of chamfer on bolt holes? I see no witness marks from the stud and washer on that bolt hole.

No, but why does the surface were the hardened stud washer sat have such a pronounced indentation from the washer? This is a 4140 material billet cap, they’re not soft. How did just torquing the nuts down on the washers do this? Aren’t the washers there to kind of spread the nuts load bearing surface out a bit more and provide a nice smooth hard surface for the nut to spin against and not dig into the cap?

 

[Unholy707]

holes too big? Thermal expansion?

 

[16GoManGoHC2]

holes too big? Thermal expansion?

Nope
Expansion kind of sort of but not thermal.
The “parts” not up to the task are in the first picture, they did not fail but they did not do what was needed of them in this case, their part number was included for a hint. If there was 4 of them not 2 of them in at least caps 2 3 and 4 they would have worked. I’ve mentioned a few material types here, I’ll give another, 8740, it’s the culprit. What’s made from 8740 in the pictures?

 

[Unholy707]

The main studs

 

[Unholy707]

So we have cap walk/ fretting, but those hardened studs are supposed to prevent that?

 

[Unholy707]

So I guess 2 bolt main isn't going to do it (regardless of cross bolts) with the fastener. But if that fastener was used in the dart block with a true 4 bolt main cap, would have been fine? So the fastener is the culprit? Why?

 

[Bobo]

No, but why does the surface were the hardened stud washer sat have such a pronounced indentation from the washer? This is a 4140 material billet cap, they’re not soft. How did just torquing the nuts down on the washers do this? Aren’t the washers there to kind of spread the nuts load bearing surface out a bit more and provide a nice smooth hard surface for the nut to spin against and not dig into the cap?

Agreed that 4140 is a very tough material, I machine parts out of it all the time. It takes a lot of pressure to indent the flat bolt surface.
Was the 8740 not heat treated correctly?

 

[16GoManGoHC2]

8740 just did not have the tinsel strength to make enough clamp load so they started to stretch and start acting like springs. More of them, like 4 studs per cap would have spread the load across more fasteners or the use of larger diameter studs but unfortunately the use of both those methods in a standard BGE Gen 3 block probably then starts to weaken the block. The answer short of a better aftermarket 4 bolt block round gave been to use a better grade fastener, a tool steel stud. Just lime arp 8740 head studs, after 25 psi of boost I was lifting heads and getting combustion gas into the coolant, replaced the 8740 studs with a torque value of 110 ft lbs with 625 studs with a torque value of 150 ft lbs and no more combustion gas into the coolant! There tinsel strength exceeded the force of head up lift and kept the joint clamped. Unfortunately arp does not offer 625 main studs but they need too!! There are companies out there that offer them but their like 3-4x the cost of regular arp studs, no difference from how regular rods bolts are x price, arp 2000 2-3x price, and 625 5x price lol, you get what you pay for no doubt! I would prefer 625 over all other tool steels because it is not susceptible to hydrogen embrittlement like so many other tool steel fasteners are. You know you can ruin some, if not all non 625 tool steel studs by just touching them with bare hands? And cleaning them with brake cleaner can ruin them period??? Yes, they can! But not 625, it’s the greatest thing since sliced bread in a high tensile strength fastener that sees repetitive load unload cycles like main and rod bolts see, especially rod bolts.
I hope this has been entertaining and enlightening too many for the time I’ve spent on this form and the other, making a post on this very important topic of and stud, material differences, and why they are so important and what to look for in this assemblies and failures to know you have to do something better or not on rebuild.

 

[stonewall]

This surface is definitely part of the puzzle, it did not look like that when first assembled. They all looked like cap Number one. Why did it end up looking like that?

I am not familiar with the internals on this engine design. and it is hard to see in photos. but I also see that the middle cap does not appear to have a provision for an end play control type brg.It may not use one for this design? and the rear brg. doesn't show the outline of the brg shell on the cap as the others do. which seems odd. Like it may have been a loose shell fit in the cap.

 

[stonewall]

Agreed that 4140 is a very tough material, I machine parts out of it all the time. It takes a lot of pressure to indent the flat bolt surface.
Was the 8740 not heat treated correctly?

I assumed (ass of you and me) that the bolt hole was counter bored for the washer seat.

 

[Jack_Toepfer]

I assumed the caps were counterbored as well, squishing a washer into the cap is not a great idea.
Are you telling me those main studs aren’t rated for 1500-2000hp? My investigation lead me to believe that they were, but I don’t know anything from personal experience.
625 is also a hot topic with Steve Morris these days as it relates to their resistance to hydrogen induced delayed fracture. Since your studs were very much intact, I didn’t think about the material.

 

[16GoManGoHC2]

I assumed the caps were counterbored as well, squishing a washer into the cap is not a great idea.
Are you telling me those main studs aren’t rated for 1500-2000hp? My investigation lead me to believe that they were, but I don’t know anything from personal experience.
625 is also a hot topic with Steve Morris these days as it relates to their resistance to hydrogen induced delayed fracture. Since your studs were very much intact, I didn’t think about the material.

A big NO! Standard 8740 ARP studs are really not much stronger than the stock bolts, really! And as proven in this build not good for 1500 let alone 2k to the tire! Not in pairs at least! Studs are like for a few reasons, they are usually not torque to yield, they are reusable (to an extent, how do you know if they yielded in use??) and generally provide a better clamp load because of the way a nut works on the stub verses threads down a hole but unless they are of a better material they are usually not much stronger then most factory torque to yield true not knock off OEM Torque to yield high grade fasteners are. 625 is good stuff, there are some build shops using what they say are the same as 625 material, bring sold as 625 material, but not stamped ARP 625 material and I highly doubt truly is 625 material. It’s sad when you really really can’t trust what you get in the same boxes any more, what’s real and what isn’t???

 

[16GoManGoHC2]

I assumed (ass of you and me) that the bolt hole was counter bored for the washer seat.

Holes where countered bored for the washers and nuts, the indentations I was referring to are inside that counterbored area, the witness marks can be seen best in pictures in post 1. Here is a close up of that original photo.

 

[16GoManGoHC2]

I am not familiar with the internals on this engine design. and it is hard to see in photos. but I also see that the middle cap does not appear to have a provision for an end play control type brg.It may not use one for this design? and the rear brg. doesn't show the outline of the brg shell on the cap as the others do. which seems odd. Like it may have been a loose shell fit in the cap.

Thrust bearings reside in the block under the middle cap, they are only 180 degrees of contact on the crank thrust surfaces and transmit their thrust load into the block not the caps.

 

[fumanchu182]

Suffered a lubrication related Rod failure but good oil pressure was present till the end, oil just stopped getting to where it needed to be for “some” reason. From the pictures and hints more ideas of the root cause? Remember the items that were the root cause of the failure are in the pictures in the first post.

If it was an oiling issue then the cause is not with the main caps. What do the journals on the crank look like. What do the oiling ports on the journals on the crank look like? The caps have one purpose, that is to keep the crank attached. That's it. What do the bearing journals look like?

 

[Spoolin]

And the inconsistency in the machined mating surface (and why not ground?) doesn't much impress me either.

Even if not ground, those surfaces should be at least a 16 or 32 finish, and consistent.

Even accounting for line honing, those caps need to not move around, and that machined finish is shit for stability...


.02

Do they not use any locating dowels on the caps? Seems that would be good to have to help eliminate any fretting.