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Old 05-24-2019, 03:15 PM   #1
twowheeledlife
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Default B230FT Top End Refresh: Am I Doing This Right?

Hey everyone, first post up on TB so beat me up as you feel suited. I have an B230FT from an 88 740 which has just over 200k miles on it which I plan to swap into my 93 240 and I'd like to do a top end refresh. For the top end here's my idea:
  • Mahle .012 over bore pistons (anyone with any feedback on these?)
  • Pull the heads and have a valve job done
  • New valves, valve springs, seats, guides
  • IPD turbo cam kit
  • New gaskets
  • Posible crank bearings
  • New front and rear seals

Aside from that I'm planning on running a 3" down pipe, manual boost controller, stock turbo for now, and am considering the wasted spark upgrade. I drive the car about 250 miles a week commuting right now and I think a mild build like this would allow it to remain a daily. Any thoughts or input is appreciated!
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Old 05-24-2019, 03:50 PM   #2
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1. What’s wrong with the car right now that you have to do all that work? You don’t need all that work just to put a cam in it.
2. What are your goals for the car?
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Old 05-24-2019, 04:26 PM   #3
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Currently the timing on the B230FT is off which I need to address and aside from that I haven't dug too much into it. My goals for it are reliability with some additional power and possibly mileage, it's a commuter car that I'd like to be able to enjoy a little more than I currently do. I figure if I am going to have the motor out of the car, I might as well refresh it while it's easy to get to and before I run into any issues. My current B230F has just under 250k on it and still runs well so I'm not in a huge rush to swap the motor. I just want to do it right the first time.
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Old 05-24-2019, 04:48 PM   #4
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Just a little note on terms since youse a noob.."Top end" means everything above the block deck surface..head, valve, cams..
Pistons are in the "bottom end"..

Personally I think you're thinking is good..Its out, the one in the car runs so you can spread the pain of the cost, so why not "rebuild it"..Good chance your crank is perfectly fine, but careful measurement ---something rarely done here when "feeling" is good enuf---often shows top ring groove worn past spec at around 200,000 miles..simple function of reciprocating cycles.. lile 200 million times the rings have banged into the top and bottom of the groove twice every revolution.. Groove wears.. Life is rough.
So common that last 20 years I I just assume top ring groove is kaputt..

That means new pistons.
That means may as well make the holes round and straight and that means bore..

I personally feel that the differential cost of cast vs forged is so low when amortised, may as well go custom forged so I can specify dish volume, dish diameter, dish top and bottom radius and compression ratio..

But still that depends on planned end use.
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Old 05-24-2019, 05:04 PM   #5
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Thanks for the insight on this. I was planning on having the cylinders bored for those Mahle pistons and had chosen cast over forged really for price and the fact that I don't plan on trying to make crazy HP or have high compression. I understand (a little) the benefits to higher compression as well as stronger and lighter pistons, combined with stronger and longer rods, but from what I've read that really comes into play once the motor build is more aggressive which I'm hesitant to do since this will still be my daily here in Texas. Also I'd like to note that I'll be swapping my AW71 for an low-ish mile (90K) M47 and don't want to blow it up with too much power which seems to be a recurring issue with them.
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Old 05-24-2019, 07:12 PM   #6
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Quote:
Originally Posted by twowheeledlife View Post
Thanks for the insight on this. I was planning on having the cylinders bored for those Mahle pistons and had chosen cast over forged really for price and the fact that I don't plan on trying to make crazy HP or have high compression. I understand (a little) the benefits to higher compression as well as stronger and lighter pistons, combined with stronger and longer rods, but from what I've read that really comes into play once the motor build is more aggressive which I'm hesitant to do since this will still be my daily here in Texas. Also I'd like to note that I'll be swapping my AW71 for an low-ish mile (90K) M47 and don't want to blow it up with too much power which seems to be a recurring issue with them.
Well if you've found a set of OEM cast they ARE good..Nothing super-duper---same mahle cast as any other Euro car of same generation but small little things make them a smidge strong than many of the OEM cast junk in US and most Japonaise pistons...
Volvos Mahles have what we call "drilled oil returns" in the slot for the oil control ring..
That makes them significantly stronger than older mahles or most Merikuhn or Japonaise so called T slot pistons which have a sawed slot in the oil ring groove..
See piccie:




Those type were notorious for developing cracks from the end of the slots down into the piston pin boss...and then dropping the top of the piston off at TDC...leaving the rod to rattle around on its own...

So if you have self control and keep a lid on the bewst you'll probably be OK (the problem with turbo cars, though, is boost is addictive...just a Leeeeeeeeeeeeeeeeeeeeetle more, then just one thin wafer, Mr Creasote, a liitle more and kaboom.

Hope the bores clean up at only 012 thou...(yikes!)
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Old 05-24-2019, 08:16 PM   #7
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What about the 88 skinny 9mm rods?
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Old 05-24-2019, 08:53 PM   #8
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Stage zero, toss the cam in and your uncle’s name is Bob
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Old 05-24-2019, 09:19 PM   #9
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What about the 88 skinny 9mm rods?
If he could find some of the scarily skinny 13mm rods it would be better than the paralyzingly scary 9mm things, of course.
God knows how many I have of those..dozens...They worth $10 each?
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Old 05-24-2019, 10:06 PM   #10
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Quote:
Originally Posted by twowheeledlife View Post
Thanks for the insight on this. I was planning on having the cylinders bored for those Mahle pistons and had chosen cast over forged really for price and the fact that I don't plan on trying to make crazy HP or have high compression. I understand (a little) the benefits to higher compression as well as stronger and lighter pistons, combined with stronger and longer rods, but from what I've read that really comes into play once the motor build is more aggressive which I'm hesitant to do since this will still be my daily here in Texas. Also I'd like to note that I'll be swapping my AW71 for an low-ish mile (90K) M47 and don't want to blow it up with too much power which seems to be a recurring issue with them.
Better to cry once. Many on here make big power with stockers. Not reliable power however.
If you want a reliable performance engine, over spec everything at least a bit. I tend to follow a 1.5 rule. If you want a reliable 300 hp, choose parts that handle 450. It leaves headroom for mistakes tuning and future upgrades.
You may not need better pistons now however the time cost to rebuild an engine as well as parts and machining cost will be double if you decide to upgrade later. People forget that the parts frequently cost a lot less than the labour to fit them.
Performance is a floating number and people always want more. If the price to upgrade to forged isn't too much, I would do it now to save the time, machining and labour later, especially if the block needs to be bored anyways. No point paying to have it bored after the cast pistons fail when you start cranking the boost knob, or put on a bigger turbo. Or throw a 150 shot at it at the track on the weekend...
If it was a low mile block that didn't need machining, and you were just throwing in flattops to raise compression, Dingle ball it and use cast.
Since you are machining it anyways, spend the money and put in the best parts you can.
Its cheaper to just put in forged now if there is any chance you will start to push it.
The old "While I'm in her" routine.
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Old 05-29-2019, 03:42 PM   #11
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Sorry for the late response guys. The more I am reading on here, it seems that I should just bite the bullet and buy the forged pistons so it's done right the first time. I know Yoshifab offers forged pistons, do any other companies and if so are they comparable in price? I am reading that stock bore is 96mm and the Yoshifab are 96.5mm, would that be enough material to clean up the cylinder walls?
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Old 05-29-2019, 06:05 PM   #12
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And H beam rods?
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Old 05-29-2019, 07:21 PM   #13
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Any suggestions other than Yoshifab for H beam rods?
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Old 05-29-2019, 08:22 PM   #14
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Your block may not be worn enough to need boring.

Yoshi does not sell 8v pistons

Mahle turbo pistons are not forged and stupid heavy and do not have a hardened pin. Over 700 grams

You don't want turbo spec if you don't have a turbo.
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Old 05-29-2019, 08:23 PM   #15
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EBay has rods
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Old 05-30-2019, 09:43 AM   #16
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Honestly Tom,

It sounds more like you've got money in your pocket and you're itching to burn it. Which is totally cool and if you have it set in your heart to do this, then by all means it's your money.

I think what people are trying to say (and maybe by people I mean me) is that if you're just looking to drive it, reliably, at stock or a little more than stock hp levels, and there's basically nothing wrong with your current motor, then just change the oil, put a new timing belt on it and go about your day. If you had started the thread saying that you want to make x00 horsepower then forged pistons and h-beam rods should be in the conversation. That's just MHO and it's worth the price you paid for it.

For stock hp, most people round these parts would just visit the local pnp and grab a motor. 250k, 300k, 350k, no worries. Pop open a 300k block, greasy and black and you still see cross hatching on the cylinders. My first project was a 1988 740 b230 small rod motor with over 300k... plopped a turbo on it and ran forever until parts started failing... like radiators and hall sensor wiring and fuel pumps... but the motor is still sitting in the shed waiting to be used again.

There's a lot more things to worry about reliability-wise with these cars than the motors.

Last edited by 740atl; 05-30-2019 at 09:49 AM..
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Old 05-30-2019, 10:20 AM   #17
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Quote:
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Honestly Tom,

It sounds more like you've got money in your pocket and you're itching to burn it. Which is totally cool and if you have it set in your heart to do this, then by all means it's your money.

I think what people are trying to say (and maybe by people I mean me) is that if you're just looking to drive it, reliably, at stock or a little more than stock hp levels, and there's basically nothing wrong with your current motor, then just change the oil, put a new timing belt on it and go about your day. If you had started the thread saying that you want to make x00 horsepower then forged pistons and h-beam rods should be in the conversation. That's just MHO and it's worth the price you paid for it.

For stock hp, most people round these parts would just visit the local pnp and grab a motor. 250k, 300k, 350k, no worries. Pop open a 300k block, greasy and black and you still see cross hatching on the cylinders. My first project was a 1988 740 b230 small rod motor with over 300k... plopped a turbo on it and ran forever until parts started failing... like radiators and hall sensor wiring and fuel pumps... but the motor is still sitting in the shed waiting to be used again.

There's a lot more things to worry about reliability-wise with these cars than the motors.
I appreciate this feedback. The idea for the motor is to be refreshed, reliable, and not make a ton of HP since I'll be running an M47 and I'd rather not shred it. I was able to pick up the donor car (88 740) for $600 so I do have some cash set aside to get it running as best as possible and for as long as possible.
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