AdrianH
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| posted on 4/5/09 at 09:13 AM |
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Any reason not to use 8.8 bolts rather then exhaust studs?
Just wondering about this after removing semi rusty exhaust studs from the head. I need longer studs so any reason why I should not use standard
bolts to secure manifold to head?
The studs just seem to be normal steel and the nuts are also steel.
Cheers
Adrian
Why do I have to make the tools to finish the job? More time then money.
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Jezzer99
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| posted on 4/5/09 at 09:19 AM |
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Not so sure the stud material is the issue but what were the nuts made from for the original manifold? On other cars (mainly old MGs) they look to be
made of some sort of alloy which I presume stops them from corroding onto the manifold studs.
Just a thought...
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nitram38
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| posted on 4/5/09 at 09:20 AM |
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The main reason I would stick with studs is if a bolt shears close to the head face, it is more difficult to remove. A stud is more likely to shear
near the nut and leave part of the stud sticking out of the head which should help with removal.
Other issues include trying to get a bolt in straight close to an exhaust bend and lining the manifold up. A nut is easier.
[Edited on 4/5/2009 by nitram38]
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britishtrident
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| posted on 4/5/09 at 09:21 AM |
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Just cut the head off a bolt to make a stud -- studs wil make it easier if you every have to take it off.
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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AdrianH
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| posted on 4/5/09 at 09:25 AM |
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I have 8 mm stainless steel threaded bar I can cut that to length and use that, I guess, would that be better as less corrosive action between
stainless and aluminium?
Bit more information, what made me think of it was the nuts will not come off the studs easily, but the studs have unscrewed from the head, I can soak
them to separate later, and I agree that using studs as support for the manifold would make fitting easier in tight corners etc.
Adrian
[Edited on 4-5-09 by AdrianH]
Why do I have to make the tools to finish the job? More time then money.
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ss1turbo
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| posted on 4/5/09 at 09:30 AM |
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There are people who swear by using stainless bolts (cap heads normally). Not convinced myself and use 10.9/12.9 grub screws; at 50mm long they do
the job and have a hex head inside them to allow for easy fitment.
Proper manifold nuts are the best to use - brass or copper. Due to the softter material, they're a longer nut to compensate so you get more
threads covered - and its usually the exposed bit of thread which suffers.
Saying that - we're comparing nuts from 10 year/100k engines with ones that do little annual mileage and we're constantly tinkering
anyway. If they come off easy after a couple of years, they why not replace them then? A couple of quid on new nuts before they get bad is better
than trying to use extractors etc..
Long live RWD...
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Mr Whippy
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| posted on 4/5/09 at 09:39 AM |
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stainless bolts - brass nuts & washers
no problem
note - same method used on gearbox belhousing but using only steel, allows parts to be supported while tightening up
 
[Edited on 4/5/09 by Mr Whippy]
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AdrianH
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| posted on 4/5/09 at 09:45 AM |
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Excellent, no problems using stainless and if my local nut and bolt place has brass nuts then that will do, time for the garage again on this wet bank
holiday Monday.
Why do I have to make the tools to finish the job? More time then money.
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BenB
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| posted on 4/5/09 at 11:04 AM |
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There is a reason why which I will try and explain!!
If you use a bolt you tighten it up good and proper. It puts a pulling force on the thread. IE the metal is under strain. Add a few heat cycles (ie
expansion and shrinking) and you can get problems.
When you use a stud you put it in place and it pulls a pulling force on the thread. However, when you then put the nut on the end and tighten it, it
neutralises this pulling force. This means that the metal around the thread isn't under the same level of strain as when using the bolt.....
This is all nicked from Corky Bell supercharged btw (well the thinking behind it, not the poor explanation- that's me....)
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gazza285
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| posted on 4/5/09 at 11:12 AM |
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quote:
Originally posted by AdrianH
I have 8 mm stainless steel threaded bar I can cut that to length and use that, I guess, would that be better as less corrosive action between
stainless and aluminium?
Not always a good idea to use aluminium and stainless together, the galvanic reaction between the two is quite strong.
DO NOT PUT ON KNOB OR BOLLOCKS!
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dhutch
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| posted on 4/5/09 at 11:17 AM |
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Not sure i agree with the explantion of how the bolt/stuf is under less force when using a stud than a bolt.
Material type apart, the two main reasons i know of studs being used is:
- Where you are likely to be removing the item alot and the base part is expensive
- Where due to tube position etc, you can get a bolt inplace.
With a stud, stud goes into block/head and then when you remove/replace the manifold it just stay there. And should the threads get worn after a lot
of times in and out, you can replace the stud and nut. Where as using a bolt, you wear the block/head threads each time, which is expensive to
replace, and can be an issue. Partiularly with aluminum heads ofcause.
If you dont have studs, then wippys comment about using steel bolts, with brass nuts/washers sounds good and is something i have seen before. Although
you will need room to get the bolt inplace.
Daniel
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BenB
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| posted on 4/5/09 at 11:41 AM |
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All to do with balancing the preload with the clamping force..... my explanation probably didn't explain it well!!!
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Mr Whippy
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| posted on 4/5/09 at 01:00 PM |
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used the stainless bolts and brass washers for years, never had a problem
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dhutch
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| posted on 4/5/09 at 01:35 PM |
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quote:
Originally posted by BenB
All to do with balancing the preload with the clamping force..... my explanation probably didn't explain it well!!!
The only thing i can think is that with a stud you will bottom it out in the hole usally, where as the bolt wont.
- Hence the end of the stud will be under some compression from being tightend against the end.
- However studs/bolts dont break at the end, they break between the last portion in the threads of the block and the nut or bolt head.
I do have agree with the comment about being slightly carefull with stainless into alumium. Because that can indeed often suffer far worse corrosion
than steel into alu (or steel)
Daniel
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iank
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| posted on 4/5/09 at 01:42 PM |
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quote:
Originally posted by BenB
All to do with balancing the preload with the clamping force..... my explanation probably didn't explain it well!!!
Not sure I understand the preload argument, and can't find anything along those lines in Carroll Smith's fasteners book, will have a thunk
about it. He does prefer studs to bolts where you are taking a component on/off a lot as it protects the thread in the block/head - difficult to
strip the female thread if you don't remove the fastener and hard to strip on fitting when you're using fingers, they also provide for a
guide for alignment while assembling.
I do know of mini racers using cap-heads rather than studs for the exhaust/inlet manifolds as there's not very much room to get them over the
studs with the engine fitted, bit of a special case that one.
I quite like Whippy's bolt-as-a-stud solution, certainly for some applications.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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AdrianH
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| posted on 4/5/09 at 01:55 PM |
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I also agree with the stud protecting the internal threads of the head.
On the stainless and aluminium, I was sure it was suggested that I should use stainless rivets when fastening an aluminium floor, they being better
then aluminium in steel?
Adrian
Why do I have to make the tools to finish the job? More time then money.
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BenB
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| posted on 4/5/09 at 02:01 PM |
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Okay well this is what Corky says!!
"A properly anchored stud, with its shank bottomed out in the block will always prove a superior fastener system to a bolt tightened onto the
block. This is because the stud's chamfer presses onto the deck surface and induces compressive stress into the material surrounding the threads
in the block, essentially "preloading" the block. When the head retaining nut is tightened, the tension in the stud has to pull this
compressive preload out of the threads before the threads become loaded in tension. Hence, the threads can take a greater tensile load."
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gazza285
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| posted on 4/5/09 at 03:45 PM |
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quote:
Originally posted by AdrianH
On the stainless and aluminium, I was sure it was suggested that I should use stainless rivets when fastening an aluminium floor, they being better
then aluminium in steel?
The aluminium rivet reacts with the steel and fails, a stainless rivet also reacts with the steel, but the rivet does not fail. The rivet will react
with the aluminium floor and the floor will develope holes eventually. You can minimise the damage by using silicone sealer on each rivet.
http://www.pilotfriend.com/experimental/build_12.htm
DO NOT PUT ON KNOB OR BOLLOCKS!
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AdrianH
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| posted on 4/5/09 at 06:30 PM |
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Thanks all for the information, ideas and links.
Adrian
Why do I have to make the tools to finish the job? More time then money.
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Peteff
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| posted on 4/5/09 at 06:38 PM |
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I took the exhaust off a Corsa the other day and only two of the studs stayed in the head anyway, all the others came out just like bolts so I
can't see any problem replacing them with bolts if you can easily get at them.
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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