Paul,
I was wondering if you or anyone could tell me if there exists a stainless
alloy that would be equivalent to 4130?
Thanks
Dean Head
Brooksville FL
Cozy #1040

First I don't know what you mean by equivalent.
Second I am no metallurgist :)

Paul Lamar

Dean,
There is no equivalent, it's horses for courses.
Stainless steel has a higher % of chromium ( up to 19%) and no (or little)
carbon.
4130 has a some chromium ( up to 1%) but has carbon (up to .3%).
4140 has .4% and 4340 has .4%
The carbon makers the steel stronger for it's weight ( heat treated and
annealed) and is therefore ( in the case of 4130) more suitable for high
flexing aircraft frames /engine mounts.
4130 is a high tensile chromium steel.
Stainless steel is a high chromium steel 302, 304 are common and SS 316
marine grade

The only place I'm using stainless steel instead of 4130 is in the rudder
pedals. They will be a little heavier to off-set the strength to weight
ratio (there are other reasons as well), this is not normally done as SS can
and will fatigue much more easily with flexing and vibration.
Hope that helps.
George ( down under)