Best Material for exhaust Nuts?

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john robert bould

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I have a old 750 with slightly loose exhaust nuts, so instead of inserts i was going to make slighty larger threads on the new home made nuts, so a better snugger fit.
What would be the best material? i have some Alloy Bronze..would that be a good choice? No doubt Jim will have made some . :?:
 
I sure like the brass or bronze ones for their feel of heft handling and taking the tough job in stride. Maybe same stuff JIm makes repair inserts out of Aluminum bronze alloy. If obsessively weight and heat flow conscience could do em like Peel in 7075 T6 and use springs to keep mostly nipped up and able to remove later.
 
Bronze or stainless are both going to have similar expansion rates to the aluminum head. That will help keep the aluminum threads intact a little longer. Jim
 
jeffdavison said:
do I sense a business opportunity?
:D

JD
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No, CNW already has good billet stainless nuts.

I use hard al/bronze thread inserts so I wouldn't want to use the same material for the nut.

The soft bronze nuts that are available are much softer than my inserts. They will loose their threads if they are run loose or are tightened too much with my hard inserts. I stick with original steel or stainless nuts. Jim
 
I've had Trixie's bronze bolts beaten in and out at least dozen times so far and so far still fine, ugh for a dozen or more to come. Peel is weight & heat conscious so will try the Aluminum versions and see what happens. Her welded up Y for 2-1 pipes may trap them on so extra hassle mess if they don't hold up long. There is so much variation in Norton kit what some get away with others can't, ugh.
 
I've been using 1975 nuts and header pipes for years on my 74 without any issues. A little anti seize on the threads and remove the header and exhaust together. No loosening of the nuts or buggered threads :D
 
comnoz said:
Bronze or stainless are both going to have similar expansion rates to the aluminum head. That will help keep the aluminum threads intact a little longer. Jim
Click to expand...

Hmmm...not so sue about that. Heat transfer rate for bronze and aluminum is similar. Heat transfer rate for stainless steel is 4 times less than Aluminum. Thermal expansion rates are another cup of tea. Depending on type of stainless and chemical make-up, it can vary in expansion rate from cold rolled steel to similar to bronze...but aluminum? Aluminum has the highest CTE (Coefficient of Thermal Expansion) of any metal...so there is no way that bronze and stainless have the same or similar thermal expansion rate as aluminum. Very different.
 
dennisgb said:
comnoz said:
Bronze or stainless are both going to have similar expansion rates to the aluminum head. That will help keep the aluminum threads intact a little longer. Jim
Click to expand...

Hmmm...not so sue about that. Heat transfer rate for bronze and aluminum is similar. Heat transfer rate for stainless steel is 4 times less than Aluminum. Thermal expansion rates are another cup of tea. Depending on type of stainless and chemical make-up, it can vary in expansion rate from cold rolled steel to similar to bronze...but aluminum? Aluminum has the highest CTE (Coefficient of Thermal Expansion) of any metal...so there is no way that bronze and stainless have the same or similar thermal expansion rate as aluminum. Very different.
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Yes, the word "similar" was a bad choice .
But austenitic stainless [like used to make a nut] and bronze are very close and both are much closer to aluminum than cast steel.
That is why I prefer a stainless nut in a aluminum bronze thread insert. They stay tight.
My next choice would be bronze or stainless in aluminum threads since an aluminum nut in aluminum threads is a recipe for disaster. Jim
 
JD. Not really. there is too many people "Knocking" these out, just a custom set for me [thread cut to suit the slighty worn original port], alu-bronze sounds the best in alloy head. those seager Ebay rose's at £96 are a bit pricey.



jeffdavison said:
do I sense a business opportunity?
:D

JD
Click to expand...
 
john robert bould said:
those seager Ebay rose's at £96 are a bit pricey.

JD
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Yes they are John, but the £96 you mention includes shipping and you get the spanner too, which really cannot slip you slide it in sideways and it is locked in...they are well made item from a company that does head insert repairs and seem to know their buisness....

You are paying about £40 each for the nuts and if you compare with standard AN nuts at around £35+ each plus VAT and shipping its not so bad....

They are really nice parts to put in my FullAuto head.....we will see what they are like in use later...
 
Steve, agree the quaility looks good, and that spanner is the business :!: Your fullauto head ain't cheap and requires the best bolt on goodies.
 
John,

I scrounged on eBay and found some used bronze rose nuts, they were listed as Norton, but when I received them, the thread was too big. The Commando is 1 15/16 from memory. So not sure if Atlas's had bigger threads? But this suited me as my head threads were already inserted, years ago by PO and a touch worn. So I machined off the threads and had enough meat to re-thread to a nice tight fit in my head. I like the look of the bronze nuts. And they do stay nice and tight.

Cheers Richard
 
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