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  1. #551
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    Quote Originally Posted by schlitzaugen View Post
    Given the design we are talking about, I think the temperatures important here are at the bridge. Ambient head temperature is of course important but only as a background (though important for the steady-state temperature). The question is whether or not fluctuations around this ambient temperature impact on the bridge and by how much (I mean are these enough to weaken/soften the bridge and eventually crack it ?).

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    Pressures are of course another factor to be considered and I have no doubt they impact seriously (even if indirectly) on the bridge longevity.
    Many years since I studied metallurgy and almost as long ago having witnessed welding of Alloy heads.

    In the dim recesses of memory I recall that a key to good welding repairs was the care and attention to stress relief after the welding process was completed and before the final machining commenced. Good weld, good stress relief meant longevity in service.

    Can't remember if it was necessary to preheat the head prior to welding like was done to cast iron heads, but much depended on the skill of the person doing the welding in each case as I recall.

    Ken

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    My machinist friend showed me the importance of pre-heating aluminium alloys before welding. One day I couldn't find him so I gave a small job to do on my sump to his neighbour. Two hours later the man called me and told me the weldings all cracked. Took the sump to my friend and he explained the more silica you have in the alloy the more important it is to pre-heat and the temperature you use. The electrodes and how you weld (he has a very schmick industrial welder - Lincoln something or other, I think) are the next chapter. Suffice to say my sump doesn't leak to this day.
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    Quote Originally Posted by 4cvg View Post
    What an extraordinarily interesting post; thank you.
    Totally agree. Fascinating. Those guys really know what they are about!
    JohnW

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    Quote Originally Posted by R8philSA View Post
    Hi there Carvel. I was just looking at your photo of the rusty disc as I have 4 on my R8 restoration (BARNIE). Did you clean up the rust on your disc or are we forced to by new discs just because they rust?? My rusty disc looks similar to yours. Cheers Phil
    Unless pitted, I've always cleaned mine by applying the brakes and it has worked well. At about 300,000 km, I finally measured the rotor thicknesses and the fronts were 0.5 mm under the minimum, so I replaced them - the first time they'd been touched. The rears were still OK, but then the pressure limiting valve had been in place up until then, so they hadn't done much work. I recall Simon commenting here somewhere that the R8 G discs you can buy are maybe 1 mm thicker but you can still just get new pads in. My NOS replacement rotors were the standard ones and not quite as true as the old ones!

    On your brakes, while I think of it, I'm very happy with my new stainless steel braided hoses, built to be legal for street use by the local brake place. Pretty well all the squish in the pedal disappeared. I'll never use NOS hoses again. Getting the free travel at the pedal exactly right made a huge difference in my case, too.
    JohnW

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  5. #555
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    Hi All,

    R8philSA........ Be careful with the rust. It does impregnate into the pads and glaze. Then you have no brakes. It is very easy and safe to remove the rust with those abrasive 3M pads that fits on a smallish angle grinder and then you can get them back to metal without the danger of removing metal.

    Back to the cylinder head. I am going to hand the head in later to get some feedback from a specialist. My explanation of that centre piece cracks are the fact that they sit dead center in the flame front AND they do not have the cooling capabilities of the other areas. The other areas are almost in direct contact with the cooling water while this little bridge piece is far away from the water and relies on the temperature to travel from the middle to the sides and from there only cooling can take place. The other definite cause of the crack is the sharp edge where the flame shoot starts. Any sharp edge is a trouble point and a weak spot.

    I will report when I get an answer back.

    Regards, Frans.
    Old enough to know better
    Young enough to do it anyway.

  6. #556
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    Fair comment Frans - my casual approach is certainly only for pretty superficial rust! I'd certainly clean them up if it were serious, not least to see what the surface really looked like before measuring things.

    The head matter is fascinating - easy for me to enjoy as it's academic at my end. Seems to me there's a much bigger and varying thermal load in that narrow flame tube area between the valve seats, let alone the shape complexity, thin sections all of it a bit remote from coolant etc. And the original is cast. Way out of my league - best of luck with the repair, that's for sure. Happy New Year to you and yours too.

    Cheers
    JohnW

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    Phil - this particular car had been standing for a while , and is only now being put back on the road with the 1420cc engine project for it completed . A bit of investigation and gentle testing with emery paper suggests that it is only surface rust similar to my other car after it stands , and riding around the block with that one with left foot lightly on the brakes seems to sort it out - although noisy at first ! ! - and the dust does not seem to affect the friction capability of the pads - but I am careful for a while until that is confirmed ! On my 3rd car they were a bit pitted and skimmed those a couple of thou even though the book says no ,

    Keep well,

    Carvel

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    I didn't see Frans' post before I replied - his points are noted in terms of glaze - and I think it is a question of degree . All I am suggesting is that in terms of my experience , light surface rust appears to respond to a light brake application treatment - but I check afterwards to make sure I still have brakes ! On a lighter note given my background I would comment that for decades , train brake shoes were made of cast iron ,

    Best regards,

    Carvel
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    And yet another comment - IF the discs are off the car , then they can be very easily cleaned using electrolytic rust removal techniques - that removes all the rust , and does not touch the base metal ,

    Regards,

    Carvel

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    All,

    Before delving into any gory details , maybe just an overview of the 1420cc motor for general interest .

    I had purchased this car more than 10 years ago and it’s been ‘waiting its turn’ as it were , which having (re) retired had a chance for some TLC this year , together with my others J

    The car was complete and in good condition even though the paintwork was a bit “tired” here and there , but the engines were in pieces ( a standard one although 0.75mm undersize, and this ‘project’ engine) .

    The previous owner had acquired a set of R5 Alpine 1397cc pistons and sleeves , and was trying to build up a motor using these with an R9 Block sub assembly and an R8G head and cam

    However he had run into difficulty with the compression ratio and push rod clearance and valve gear geometry , and had effectively abandoned the project – also due to ill health and time .

    I had been is discussion with Salv Sacco in the UK regarding pistons for my 1340cc motor , and the topic of his 1420cc racing motors based on the R5 Alpine engine came under the spotlight , and to cut a long story short I bought a set of pistons used in his motor which were 76,5mm bore , domed and pocketed .

    As a first step the R9 block was pin bored to accept the 21mm Gordini cam followers , and recesses were ground in the side walls of the sleeve support area as per a Gordini block to allow the use of R8G push rods and for them to clear

    The camshaft was an early “Alp70 “ grind which we saw in SA , and was moderately sporty with 7mm lift , and 32-66/66-32 timing

    The R9 crank , flywheel , and conrods were used , with the conrod small ends being bushed to allow for the floating gudgeon pin design of Salv’s pistons , and the whole lot balanced

    The head had been skimmed a few times in its life , so it was built up with the aluminium metal spray technique to bring the CR back to 10.5 : 1 , and larger inlet valves were fitted . ( I am not in Frans' league , so this is a sporty road use car )

    I used the 38mm diameter , 7mm stem inlet valves from the original Suzuki GS1000 bike and they worked out very nicely with minimum modifications

    This sub assembly , head and valve gear combination seems to work , so apart from a host of other niggly little details , the project took shape .

    A deeper sump with longer oil pump pickup was fitted , and a different style of oil filter adapter for the oil cooler plumbing was necessary due to the bulge in the R9 block on the timing cover end to accommodate the spring type rather than hydraulic timing chain tensioner .

    Based on my and Salv’s calculations we should see about 140 – 150 BHP at 7500rpm out of this engine , but time will tell,

    Keep well,

    Carvel
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  11. #561
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    Quote Originally Posted by CarvelSA View Post
    And yet another comment - IF the discs are off the car , then they can be very easily cleaned using electrolytic rust removal techniques - that removes all the rust , and does not touch the base metal , Regards, Carvel
    There've always been odd advertisements about rust prevention by applying a potential difference to body. Do you have details about how you'd remove rust from rusty components please? Good to have you on Aussiefrogs too!

    Cheers
    JohnW

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  12. #562
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    John - thanks for kind words . I have been "on" Aussiefrogs for years in a manner of speaking as I would have a look now and then to see what Frans and others that I originally knew from SA were up to , but I never realised until now that out-of-country members were accepted ! So I thought if I registered it might be easier to stay in touch rather than roundabout through email , particularly as my ISP seems to have issue with some of the email addresses ! !


    The electrolysis technique is quite straight forward but I must warn up front that it is for ferrous components . Any non-ferrous parts ( aluminium , brass, bronze etc ) will get damaged . With that out of the way it does work very well with ferrous components and I first came across it with the vintage tool restoration guys .

    All one needs is a suitable DC current source - an old fashioned battery charger will do , a plastic container , a piece of sheet metal or rod(s) to act as the positive electrode , some washing soda , water , and a rusty part .

    Mix up a solution of 10 litres of water and a couple of table spoons of washing soda in your container , dangle you rusty part together with the electrode in the solution with the +ve terminal to the electrode and the -ve terminal to your rusty part and switch on . Hydrogen bubbles will form on the surface of the part ( note flammable so use in ventilated area) . After a while depending on the current you will note that the rust has been blown away and a soft black lower order ferrous layer is left behind .

    Take out the part , rinse , and wash the black stuff off with some kitchen cleaner and a scotch pad , and you should have a nice clean part

    The time taken is dependent on your current supply and the size of the part - if it is a large part and the current is low , just leave it in longer - the beauty is you can leave it in as long as you like as the base metal is never affected - once the rust is off it will just make bubbles . The solution will get brown and dirty looking but that is coming off the electrode - not your part !

    The process is scalable and is limited only by your imagination - I have cleaned tractor rims in a cut open 200 litre tank and a 300 amp DC welder ! Another chap dug a pit , lined it with plastic , filled it with solution , and dumped his whole chassis in it !

    Suggest experiment with a small container , your battery charger , and a rusty bolt to start with and see how you like it though !

    Regards,

    Carvel
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  13. #563
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    Electrolytic cleaning postscript :

    The solution looks dirty but it is actually a ferric solution which is rusty in colour

    The solution does not get "used up" - it does get warm and can evaporate , but just add more water

    The electrode does however slowly get eaten away , and may need to be scraped clean if the current flow reduces

    The solution is non-toxic and environmentally friendly from a disposal point of view if the occasion arises

    Do not be tempted to use stainless steel for the electrode - it releases chromium compounds into the solution which are toxic

    Regards,

    Carvel

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    That's great information - I've never seen a plain language description and so many times since about 1966 have needed this, or at least could have used it.

    Another good use for my old school battery charger!

    Many thanks, and double welcome!
    JohnW

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    Quote Originally Posted by CarvelSA View Post
    Electrolytic cleaning postscript :

    The solution looks dirty but it is actually a ferric solution which is rusty in colour

    The solution does not get "used up" - it does get warm and can evaporate , but just add more water

    The electrode does however slowly get eaten away , and may need to be scraped clean if the current flow reduces

    The solution is non-toxic and environmentally friendly from a disposal point of view if the occasion arises

    Do not be tempted to use stainless steel for the electrode - it releases chromium compounds into the solution which are toxic

    Regards,

    Carvel
    Hi CarvelSA,

    I am currently competing in the ZA Historics in a Renault R8. I note that you are from JHB and would like to make contact with you. I live in Himeville, Southern Berg. My FB page log on is my name and my e-mail is [email protected]. Look forward to hearing frm you.

    Regards,

    Arthur Eggar.

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    Thanks Carvel. I'll keep going with the clean-up of my discs taking into account what you have written. I dont have pitting but very rusty on the surface. I'll clean it up with emery/wire brush until it shines as long as it stayes uniform I recon it will work.
    Cheers Phil



    Quote Originally Posted by CarvelSA View Post
    Phil - this particular car had been standing for a while , and is only now being put back on the road with the 1420cc engine project for it completed . A bit of investigation and gentle testing with emery paper suggests that it is only surface rust similar to my other car after it stands , and riding around the block with that one with left foot lightly on the brakes seems to sort it out - although noisy at first ! ! - and the dust does not seem to affect the friction capability of the pads - but I am careful for a while until that is confirmed ! On my 3rd car they were a bit pitted and skimmed those a couple of thou even though the book says no ,

    Keep well,

    Carvel

  17. #567
    1000+ Posts REN TIN TIN's Avatar
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    Quote Originally Posted by JohnW View Post
    That's great information - I've never seen a plain language description and so many times since about 1966 have needed this, or at least could have used it.

    Another good use for my old school battery charger!

    Many thanks, and double welcome!
    If you can get a hold of the October 2016 edition of Practical Classics magazine it has an article on this rust removal method.
    I have a scan of the article but it's too big (6.5MB) for an attachment.
    It may also infringe copyright.


    Cheers
    RTT
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  18. #568
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    Quote Originally Posted by REN TIN TIN View Post
    If you can get a hold of the October 2016 edition of Practical Classics magazine it has an article on this rust removal method.
    I have a scan of the article but it's too big (6.5MB) for an attachment.
    It may also infringe copyright. Cheers RTT
    Many thanks. I should look more often at Practical Classics!
    JohnW

    Renault 4CV 1951
    Renault R8 1965
    Renault Scenic 2005 (wife's)
    Renault Scenic 2007 (mine)
    Peugeot 306 XT 1995 (daughter's)
    CitroŽn CX Pallas 1980

    National Co-ordinator, Renault 4CV Register of Australia

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