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Rod bolts (again)


PeterK

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So .....

Using Wayne's engine book & the Bentley manual, I have torqued my new rod bolts to 20Nm, then turned through 90'.   Now while looking for sealant info, I read that that 20Nm+90' is wrong (maybe as high as 75Nm, and too close to the yield point of the 10mm bolts) and I should have just used 50Nm.

A new set of nuts & bolts from Porsche is just over £325 (ouch).

 

Options

1 - just carry on with my rebuild - many people will have used the 20Nm + 90', so it can't be that bad (can it ?)

2 - pay Porsche £325 and suck it up

3 - buy a cheaper set of bolts from one of the well know vendors (about £125, but provenance unclear)

4 - buy ARP bolts & nuts (no idea on price, but would need to buy / make / borrow a stretch gauge)

5 - something else.

 

 

Please discuss

 

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No need for ARP on a proper engine 😇 but at £325 for standard, ARP are probably cheaper !

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Isn’t the other option (I could be totally wrong) Porsche 993 turbo bolts as these fit as strong  as ARP’s - not sure on price

Edited by Beaky
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49 minutes ago, Beaky said:

Isn’t the other option (I could be totally wrong) Porsche 993 turbo bolts as these fit as strong  as ARP’s - not sure on price

Are you thinking of head bolts Beaky ? 

Edited by GaryH
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10 minutes ago, GaryH said:

Are you thinking of head bolts Beaky ? 

Could be, I just remember in my engine rebuild research turbo bolts were an option for something!

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The proper (SC) engines had 10mm rod bolts, but from 3.2 Porsche went to a 9mm rod bolt.

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Head studs guys, studs, black fully threaded are dilavar, steel arent fully threaded

Easy enough to google "black 8" stud"...................................then go to images and see :blink:

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2 minutes ago, Type911 said:

Easy enough to google "black 8" stud"...................................then go to images and see :blink:

Ha ha - back in the day we used to tell new people at work that we were out of pens and they should go to Pen Island dot com for replacements :lol:

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You're a naughty boy, Mr Matt 😂

 

In my youf it was send the receptionist to the motor factors for a water pump for a Beetle, a long stand or a bucket of steam.

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On 30/10/2020 at 16:30, PeterK said:

So .....

Using Wayne's engine book & the Bentley manual, I have torqued my new rod bolts to 20Nm, then turned through 90'.   Now while looking for sealant info, I read that that 20Nm+90' is wrong (maybe as high as 75Nm, and too close to the yield point of the 10mm bolts) and I should have just used 50Nm.

A new set of nuts & bolts from Porsche is just over £325 (ouch).

 

Options

1 - just carry on with my rebuild - many people will have used the 20Nm + 90', so it can't be that bad (can it ?)

2 - pay Porsche £325 and suck it up

3 - buy a cheaper set of bolts from one of the well know vendors (about £125, but provenance unclear)

4 - buy ARP bolts & nuts (no idea on price, but would need to buy / make / borrow a stretch gauge)

5 - something else.

 

 

Please discuss

 

If you've got new rod bolts (12.9) and new nuts and youve done it IAW with what you've detailed. Option 1.  

Don't over think it. 

 

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I went through a similar quandary on rod bolt torques when I did my first 3.2 rebuild. I probably did overthink it, but you may find the info in my thread below useful:

 

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Thx

So overall, just crack on with my build 👍

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Thanks all.

Although I am almost certainly OK, I’m wimping and replacing the bolts.

Anyone need a set of nuts & bolts, tightened once but never run 😂

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4 hours ago, PeterK said:

Thanks all.

Although I am almost certainly OK, I’m wimping and replacing the bolts.

Anyone need a set of nuts & bolts, tightened once but never run 😂

I don't know why you are worried, according to MaxD's link half the specialists in the UK don't know how to torque down the big end caps. 😃

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5 hours ago, ras62 said:

The initial 20nm plus 90 results in 45 lb/ft which is correct, about 50nm. A little grease under the nut to stop binding.

A little grease ? I'm no expert but they should spend their lives bathed in oil. 

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  • 4 weeks later...

Peter, you did the right thing in buying rod bolts. I was in a recently rebuilt 911 a few years back which had a rod bolt go, its not pretty but luckily happened at low revs albeit pulling onto a dual carriageway. I rebuilt it for them and used ARP with a stretch gauge, job done. It easy to be blase about these things until you hear an engine actively trying to tear itself a new one.

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