I'm not good at math but it seems to be the stock one wins.
Yet another great job by Jim!
I'm pretty sure I said I wasn't good at math, right? Did I miss the part where you measured the exhaust port expansion?
No, but I did measure a cast aluminum nut -similar to the head.
So why isn't the alu nut the winner if criteria is same expansion as head?
But the mass of the head is going to expand differently than a smaller nut?
Shouldn't be terribly hard to measure the exhaust port, you only have to do it once.![]()
The expansion of the head should be similar to the nut. The expansion will be determined by the circumference of the hole in the head -just like the nut.
A head won't fit in my small oven.
And the larger oven that I use for heads only goes to 400 degrees.
And I am not going to fire up my big oven just to test one head. Maybe I will test the idea when I have a batch of barrels to stress relieve.
comnoz
the measurements of the AN and RGM parts are almost identical to mine but the RGM didn,t fit either RH4 or Fullauto head.
There are signs in your video of potential trouble in the tightness of the RGM part, it shouldn,t need oil to screw freely into the Fullauto, which the AN one does easily and when tightened correctly into good threads doesn,t loosen off in my experience. (on Commandos or Atlas)
Your own data on the recent dash6 post in fact shows that steel is actually closer to aluminium than the stainless alloy used for exhaust nuts, which is much higher, together with a higher hot expansion nearly twice that of the steel nut in your test.
This would explain why the OE steel nuts work well when everything is in good order, on older heads things have deteriorated, but nothing properly machined inserts won,t fix and at the end of the day, while bench testing is important, it,s what happens during longterm everyday riding that counts in this case.
comnoz
I,m with swooshdave on this one, your cold measurements of the AN and RGM parts are almost identical to mine but the RGM didn,t fit my RH4 or Fullauto heads.
There are signs in your video of potential trouble in the tightness of the RGM part, it shouldn,t need oil to screw freely into the Fullauto, which the AN one does easily dry and when tightened correctly into good threads doesn,t loosen off in my experience. (on Commandos or Atlas)
Your own data on the recent dash6 post in fact shows that steel is actually closer to aluminium than the stainless alloy used for exhaust nuts, which is much higher, together with a hot expansion nearly twice that of the steel nut in your test.
This would explain why the OE steel nuts work well when everything is in good order.
On older heads things have deteriorated, but nothing properly machined inserts won,t fix and at the end of the day, while bench testing is important, it,s what happens during longterm everyday riding that counts in this case.