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Old 09-13-2021, 08:32 PM   #1
Msi
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Default 500ish crank HP - do I need forged pistons?

Hello fellow TBs!!!

I seek your collective wisdom with some difficult questions that have been keeping me up at nights lately.

The setup is as follows:

Stock b230fk bottom + b234 head using all Yoshifab stuff for the 16v conversion. Including a set of uprated valve springs and ARP head studs. HG is stock Elring at this time.

The air comes from a 500hp rated BorgWarner EFR-6758-0.64-WG turbo through a big intercooler I got from here:
https://www.classicswede.co.uk/74094..._16513751.aspx

The fuel comes from a 255lph walbro (probably a knock-off but works flawlessly thus far) through a decent adjustable FPR and a set of 80lb/h Siemens Deka's.

All this is orchestrated by Vems ECU with 4*EGTs, 4*R8 coils on plug, oil and fuel pressure monitoring, and more.

I really want to harness the full potential of that turbo.

The stock bottom end being the elephant in the room. So, my question is - do I only upgrade the conrods? Or also go for forged pistons? And should I opt for main studs or stay with the bolts (new stock)?

Paraphrasing with some numbers and options:
Should I just source a set of maxpeeding rods with ARP bolts for 250usd shipped?
Or, do I need to go for a forged piston/rod set, which I can source from Yoshifab for 1,180usd shipped? Not to mention I'd be getting myself into machining a block for the oversize pistons.

P.S.: just to get this out of the way - I'm probably going to upgrade that fuel pump and will definitely get a decent tubular exhaust manifold and intake manifold (both of which are stock at the time).

The car, 1998 945, is not a DD but also not a beater/missile. It will drive itself to drift events and training sessions as well as the occasional Volvo meets and trips with fellow enthusiasts. Or just a weekend drive looking to troll some VAGs and Civics. It has an AC and a heater, and so it shell remain :D.

It was a bit long, thank you for bearing with me.
Cheers!!
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Old 09-13-2021, 09:41 PM   #2
RvolvoR
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Not trying to burst your bubble, but a 6758 likely isn’t going to get you to 500hp. You’ll be way out on the end of the map trying that.
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Old 09-13-2021, 09:55 PM   #3
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Hit up Hubert to get some 20 year old information.

And then get yelled at.
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Old 09-14-2021, 03:49 AM   #4
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Quote:
Originally Posted by RvolvoR View Post
Not trying to burst your bubble, but a 6758 likely isn’t going to get you to 500hp. You’ll be way out on the end of the map trying that.
Yeah. I figured it's going to be more like 450. Still, my question stands.
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Old 09-14-2021, 03:59 AM   #5
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Quote:
Originally Posted by fatcatbestcat View Post
Hit up Hubert to get some 20 year old information.

And then get yelled at.
Is that your way of saying - don't cut the pistons corner? Or "he who pays cheap - pays twice"?

I hear you

The reason I'm asking is that we have crazy customs laws and the 1,200usd set from Yoshifab will end up costing me full 1,800usd. The cylinder machining is 500usd here.

This is 10 times the price of H beams.

So I don't want to do it unless it's really necessary.

And I've read contradictory info here on TB. I saw Kenny "linuxman" saying that he pushed 500whp on stock turbo pistons. Others say that beyond 350 I should get rods and pistons.
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Old 09-14-2021, 06:21 AM   #6
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Stock pistons have been proven to higher numbers, just stay away from knock and increased piston speed. Forged buys you safety margin in the case of that. It's all in the tune and fuel, with race gas/e85 you should be okay, although the end of the compressor map might get knock prone due to the heat.

If you go with the maxspeeding rods, get genuine ARP's, that should give some piece of mind. The head needs proper tying down, the bottom end bolts are already a pretty big grade 10.9 setup, those should hold. If you go ARP you need to grind down the studs there, since the oil transfer tube will interfere.
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Old 09-14-2021, 04:33 PM   #7
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Quote:
Originally Posted by Swedbrick View Post
Stock pistons have been proven to higher numbers, just stay away from knock and increased piston speed. Forged buys you safety margin in the case of that. It's all in the tune and fuel, with race gas/e85 you should be okay, although the end of the compressor map might get knock prone due to the heat.

If you go with the maxspeeding rods, get genuine ARP's, that should give some piece of mind. The head needs proper tying down, the bottom end bolts are already a pretty big grade 10.9 setup, those should hold. If you go ARP you need to grind down the studs there, since the oil transfer tube will interfere.
I appreciate your time and effort. Thank you. That's exactly the kind of input I was looking for.

Spasiba!!
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Old 09-14-2021, 04:57 PM   #8
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Someone just posted some rods and pistons for sale in the For Sale forum. For a 16V engine too. Might be worth checking out. My target is 450-500 Crank HP, and I went with customer pistons (I did buy an engine with them already) but I would have got them regardless, just for the overhead oopsie protection.

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Old 09-14-2021, 05:59 PM   #9
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Quote:
Originally Posted by Swedbrick View Post
If you go with the maxspeeding rods, get genuine ARP's, that should give some piece of mind.
Just ordered these (says to include ARP 2000bolts):
https://www.maxpeedingrods.co.uk/pro...s-conrods.html

Quote:
Originally Posted by Swedbrick View Post
The head needs proper tying down
A fellow TBer, Harlard, came through and I purchased a set of ARP head studs from him. Keeping the stock HG as a "fuse". In case of an oopsie I hope that it will give in first.

Quote:
Originally Posted by Swedbrick View Post
the bottom end bolts are already a pretty big grade 10.9 setup, those should hold.
Could not find a source for a set of new, stock, main cap bolts. Maybe someone has an idea (with a link) where to get those?

I know that those are good for reuse but don't want to be stuck with a potentially bad bolt that'll hold back the block re-assembling.

Cheers!!
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Old Yesterday, 02:15 PM   #10
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The Maxspeeding Rod ARP's are known fakes iirc. I'm running them in my engine, but that only aims for around 300. Hasn't exploded yet haha

The stock head gasket is great, so that should do nicely. Make sure you get a real elring;)

The bolts holding the crankshaft are a standard metric size, just make sure to get the grade right. Is the engine currently on a stand? I don't recall the size, possiblity someone here can measure up. The flywheel bolts are the same standard metric deal, much cheaper to buy in bulk
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Old Yesterday, 06:37 PM   #11
Msi
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Originally Posted by Swedbrick View Post
The Maxspeeding Rod ARP's are known fakes iirc.
I felt like the price is too good to include real ARPs. Thank you for the heads up!!
Could I replace those with a set of real ARP 2000s? I mean, are the fake ones shipped with the rods at least of identical thread size to the real ones? So a genuine set could be used instead? Those are 10mm, right?

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Originally Posted by Swedbrick View Post
The stock head gasket is great, so that should do nicely. Make sure you get a real elring;)
I'm prolly good here. Got mine in a set of 16v head gaskets from -
https://www.classicswede.co.uk/B234_..._14056830.aspx

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Originally Posted by Swedbrick View Post
The bolts holding the crankshaft are a standard metric size, just make sure to get the grade right. Is the engine currently on a stand?
That's good info!! The car is a runner but I got a different, but identical, block in pieces. I'll measure there. Thank you!!
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Old Yesterday, 07:46 PM   #12
Msi
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Just got emailed by Maxpeedingrods saying that they are out of stock and should be back "by the end of this month".

Yoshifab too seems to be out of stock at the moment for the 152mm H-beams. But says he's "expecting some shortly".

None available in stock at www.classicswede.co.uk either.

Damnit. Back to square one.
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Old Yesterday, 08:35 PM   #13
Msi
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Josh came through.

----
On Thu, Sep 16, 2021, 2:53 AM wrote:
I was mistaken, I have 152mm on the shelf ready to ship today.

-Josh Sadler
Yoshifab.com
(760)468-7002
----

I'm a happy TBer once again.
Thanks everyone for the help.
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Old Yesterday, 08:40 PM   #14
Msi
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P.S. I'll leave this here for anyone looking for a set of ARPs for the 152mm connecting rods:

ARP 2000 Con Rod Bolt

ARP con rod bolts 3/8x1,5"

Bolt: 3/8" (9.53mm)

Lenght: 1.5" (38.1mm without bolt head)

Tightening with ARP-grease: 62Nm

ARP part number: 2006207 - Rod Bolt Set (8 Piece)
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Old Today, 09:47 AM   #15
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Quote:
Originally Posted by Msi View Post
I felt like the price is too good to include real ARPs. Thank you for the heads up!!
Could I replace those with a set of real ARP 2000s? I mean, are the fake ones shipped with the rods at least of identical thread size to the real ones? So a genuine set could be used instead? Those are 10mm, right?
The real ARP's fit, most H-beams are produced in the same place, difference is in post production finish and checking. I used a 11mm 12-point socket to install the bolts, probably a non-metric size in actuality. The Yoshifab stuff is the good kit, should be a nice addition to your build!
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