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Old 02-14-2019, 01:41 PM   #1
pploco
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Default "soft block" concerns

I'm building a moderate STI motor (<350hp) for a Porsche 914 conversion. I started with a 2007 EJ257 703 short block that had a spun bearing (w/50K miles). During tear down, everything looked decent. I picked up some Manley forged pistons (99.75mm), ARP studs, and took the block to the machinist to be cleaned and bored.

He calls a week later and said that as he was torquing down his torque plate with the ARP studs, one of the threads pulled. He said that he went ahead and installed a timesert and started again. Another thread pulled. He also said that he called his torque plate supplier to validate and got on call with ARP to make sure there wasn't anything abnormal. ARP said that this type of issue is "common" in over 50% of the STI blocks and that they strongly recommend timeserting all of the threads. It wasn't a huge cost, so I had him go ahead.

Now, this isn't really a thread about the ARPs or the torque plate, Subaru quality, or a shady machinist so back away from the keyboard if you're thinking of starting a flame fest. This guy does all the Subaru machining for two of the local dealerships and the largest Subaru shop in the area - he knows his ****. He was actually super cool and didn't charge me for the labor to put the caseserts in.

My question is this: Am I going to see this "soft block" issue pop up in other areas? Like the case bolts stripping? I'm a little nervous..
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Old 02-15-2019, 10:45 AM   #2
pploco
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wow... tough crowd. <tap> <tap> is this thing on?
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Old 02-15-2019, 11:01 AM   #3
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I cannot speak to your concerns on the sTi block being "soft"

however, the activity on this entire forum in general has crested and fallen off like lead weights were attached and tossed into a neighbor's back yard like last night's bad left overs. Tumble Weeds are more active than most NASIOC subforums.

All areas, all years, all posts are NOTHING like they used to be. NASIC used to be the only "go-to" place for information and abuse regarding anything Subaru.

People just don't use forums like they used to. Especially younger/newer/hipper owners, even of old cars, they rely and focus almost exclusively on social media. Therefore finding the local shops/clubs/groups/meets becomes more and more critical. With that so does your need to sharpen your BS-detecting skills and people just plain trying to sell you something.

I would ask this question of major Subaru engine builders, IAG, Equilibrium, Crawford, Grimmspeed, etc .. Then remember to show your appreciation by buying through the proper channels and supporting those who support you. Not preaching, just really laying out the current climate and landscape.

In my feeble and humble view/opinion: the car community has gone "clich-ish" in the last few years, like the Preps vs the Greasers vs the Jocks vs the Stoners vs the Goths in HS depending on your personal timeline(age) for frame of reference.

~Rob
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Old 02-15-2019, 11:14 AM   #4
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It is not often that I see the threads pull out of the case for the head studs. While it does happen it's pretty rare, UNLESS I get a motor in that someone has built before and just beat up while they assemble.

Here's the other thing about Subaru cases. They are literally a floppy bag of aluminum that holds the guts in. When reusing the case you need to not only bore and hone with torque plates, but also have a line bore done on them. The mains shift considerably.

Quite often the cost of having GOOD machine work done meets or exceeds the price of a brand new case from Subaru. This is why many of the good engine builders will start with a fresh case as opposed to reusing an old one.

If you are having doubts about this case start with a fresh one.
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Old 02-15-2019, 12:00 PM   #5
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Quote:
Originally Posted by pploco View Post

My question is this: Am I going to see this "soft block" issue pop up in other areas? Like the case bolts stripping? I'm a little nervous..
You very well might. I mean it's aluminum after all.
Not sure what you mean by 'soft block' as that would mean an aluminum block, so yes, it's soft.
Unlikely its any softer than any other block by a legitimate amount but who knows.

We do tons of aluminum tapping for applications a lot more important than a subaru block, and more often than not customers who are using aluminum spec that an insert be used right out of the gate.
So in reality with aluminum, inserts aren't always just a 'repair' solution, they are the initial solution when the designer knows that at the end of the day it's aluminum and the threads are nowhere near as strong as steel.

We use inserts that actually stake in with four stakes all around.

I wouldn't be too concerned about this, maybe just nip it in the bud and tell them to insert everything.
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Old 02-15-2019, 12:07 PM   #6
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You make some great points. What's odd to me is that I've built (and severely punished) several turbo EJs over the years and this is the first I've seen head studs pull - yet ARP claims its a common issue. I did have one block that during reassembly cracked where the idler pulley mounts. But that block had come from a head on collision salvage.

I think I'm too far into this to start over. If the block bolts torque without issue, I think I'll be okay for the kind of mild power I'm targeting.
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Old 02-15-2019, 01:49 PM   #7
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yeah, who knows what happened to it

regardless, the right insert will not only be good as new, but good ones increase the pull out strength way beyond what aluminum can hold
Some inserts we just did a few hundred of thread into a 9/16-12 hole in the aluminum but the insert thread in 3/8-16, plus they stake in on top of it.
That's why they are so good, the insert holds the aluminum with that big 9/16 thread, but the actual load on it is only from a 3/8 bolt. So that sucker ain't moving.
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Old 02-15-2019, 01:51 PM   #8
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Quote:
Originally Posted by rtv900 View Post
yeah, who knows what happened to it

regardless, the right insert will not only be good as new, but good ones increase the pull out strength way beyond what aluminum can hold
Some inserts we just did a few hundred of thread into a 9/16-12 hole in the aluminum but the insert thread in 3/8-16, plus they stake in on top of it.
That's why they are so good, the insert holds the aluminum with that big 9/16 thread, but the actual load on it is only from a 3/8 bolt. So that sucker ain't moving.
FWIW we've stopped doing 1/2" head studs here unless they do an insert. We don't like the idea of cutting fresh threads over the old ones.

I keep wanting to take a block of aluminum, tap it for a stock stud, then tap for a 1/2" and waterjet it in half to show people... alas time is lacking.
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Old 02-15-2019, 10:46 PM   #9
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Quote:
Originally Posted by Turn in Concepts View Post
FWIW we've stopped doing 1/2" head studs here unless they do an insert. We don't like the idea of cutting fresh threads over the old ones.

I keep wanting to take a block of aluminum, tap it for a stock stud, then tap for a 1/2" and waterjet it in half to show people... alas time is lacking.
My engine builder, (well known in my part of the country), won't do the 1/2" either.

He had a couple pull out. (At least one was on a running engine-started pushing coolant I believe, noticed on disassembly.)
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Old 02-16-2019, 12:14 AM   #10
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Thanks for the responses. This is helpful.
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Old 02-16-2019, 10:39 AM   #11
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Everyone not doing 1/2", are you guys opting for the arp 625's?
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Old 02-16-2019, 10:17 PM   #12
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The shop that built my block installed 14mm studs on a used case, and arp case bolts all around. Never mentioned used cases having issues with studs pulling. Sleeved and pinned block with stainless o rings. I've never heard someone mention the used cases being "soft".
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Old 02-17-2019, 12:45 AM   #13
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I think 14mm is big enough to completely remove all the old threads though, while 1/2 is not.

Maybe the shop is going too far, either due to a misunderstanding of the spec or a mis-calibrated torque wrench? Although ca625+ stock diameter studs have a final spec of like 100lb-ft, right? standard arps used to only be like 60 and then it crept up over the years.
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Old 02-17-2019, 09:39 AM   #14
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^^^^I too thought about an out of calibration wrench. Also, yes, the ARP2000 value was much lower initially and is not 85 ft-lb if I recall.

I also haven't found this to be a common issue. I'd say ARP is grossly exaggerating as they probably only get calls when something is wrong. It is more common on the case bolts using ARP's torque values.

It is however common practice in race engines to insert for aluminum assemblies that come apart frequently. Then add in that this cast aluminum with higher than designed torque, it can happen. It sucks. How to fix it would be do inserts on what you already have and suck up the difference in cost vs getting another block and potentially, though small, have the same issue and repay for the same work.
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Old 02-17-2019, 04:20 PM   #15
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Quote:
Originally Posted by TDagen View Post
Everyone not doing 1/2", are you guys opting for the arp 625's?
i did.
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