rod burner
are you sure it is chrome molly ?
i have been around karts since 1959 and 4130 frames are rare there are some but very few (cost)
probably won't matter though 1016 and 4130 have been put together before just get the right rod/i usually pre heat and post heat any molly if o/a or heliarc( that dates me )just to make me comfy/ on most of the kart frames i use 309 if i don't know/ i know there will be some questions on the forum about this prosess but it has worked for me but listen to the good guys out ther that have more smarts than me
good luck pat from tx