Triton Thrasher said:Going from 1.700" to 1.690" looks like 10 thou (0.010") undersized to me.
kommando said:The crank was not hardened but left soft for shell bearings, a useful way to extend big end life is ammonia nitriding.
Doubt you will find a 60 thou oversize bearing unless some other application in another engine was to fit, there was a guy who ordered non std under sizes up to 80 thou undersize bearings for the Triumph Dolomite Sprint engine back in the 80's but all trace of him has disappeared.
mmmmm…..what :?: :shock: ..... news to me that the big ends are not hardened and temped :?:
kommando said:mmmmm…..what :?: :shock: ..... news to me that the big ends are not hardened and temped :?:
Just take a file and draw it over a non critical surface, it will mark easily like mild steel does, just confirmed it on my 750 crank, took no effort to make a scribe line using the edge of a file.
by comnoz » Sat Dec 07, 2013 5:26 am
I have sliced up and tested a stock crank. It tested 48rc everywhere- cheeks, shafts and crankpins. I have not seen any sigh of post cast heat treatment. Jim
kommando said:Note Jim Comnoz has cut a complete crank and did hardness tests.
commando-crankshaft-porn-t8365-480.html
by comnoz » Sat Dec 07, 2013 5:26 am
I have sliced up and tested a stock crank. It tested 48rc everywhere- cheeks, shafts and crankpins. I have not seen any sigh of post cast heat treatment. Jim
My own crank and the T120 and the 2 B25 cranks I have are all soft with no sign of hardening, never saw it being done when I worked at the engine factories in Austin Rover in the 80's (exception was the Triumph Stag crank, this was hardened but I never saw that line), the latest engines were then polished after grinding but still not hardened.
making the crankshaft journal a sacrificial metal in lieu of the readily changed and relatively inexpensive bearing shell
texasSlick said:I repeat ... If the journals are not case hardened, then they should have been. It is disappointing to think Norton took such a cost saving measure, making the crankshaft journal a sacrificial metal in lieu of the readily changed and relatively inexpensive bearing shells. The main journals are in ball/roller bearings, and hardening is not required, and likely not desirable.
This is good information to know. If I ever open up my Atlas again, I will harden the journals, either by nitriding, or by the simple method of a dirty oxy-acetylene flame. The auto industry method is usually induction.
Slick
Rohan said:texasSlick said:I repeat ... If the journals are not case hardened, then they should have been. It is disappointing to think Norton took such a cost saving measure, making the crankshaft journal a sacrificial metal in lieu of the readily changed and relatively inexpensive bearing shells. The main journals are in ball/roller bearings, and hardening is not required, and likely not desirable.
This is good information to know. If I ever open up my Atlas again, I will harden the journals, either by nitriding, or by the simple method of a dirty oxy-acetylene flame. The auto industry method is usually induction.
Slick
A lot of cars used cast iron cranks, nice soft journals.
Perfectly satisfactory, as long as the oil is changed regularly.
As JM points out.
kommando said:Note Jim Comnoz has cut a complete crank and did hardness tests.
commando-crankshaft-porn-t8365-480.html
My own crank and the T120 and the 2 B25 cranks I have are all soft with no sign of hardening, never saw it being done when I worked at the engine factories in Austin Rover in the 80's (exception was the Triumph Stag crank, this was hardened but I never saw that line), the latest engines were then polished after grinding but still not hardened.by comnoz » Sat Dec 07, 2013 5:26 am
I have sliced up and tested a stock crank. It tested 48rc everywhere- cheeks, shafts and crankpins. I have not seen any sigh of post cast heat treatment. Jim