What is the HP limit of a Molnar crankshaft. Or should I say one that you would be comfortable with?

I'd call Molnar and ask Tom directly.
He struck me as a pretty straight shooter.
The piece with my 408 kit checked all the boxes and I would be confident throwing much more than I am going to at it.
For off shore and inexpensive , I really like it.
But if I was going full on , pants down and look out , I would probably go a different direction.

900

I would suspect that a big block crank could go into 4 digits , but not too far.
The usual suspects come into play too...............reciprocating weight , tune , etc.

Tom will tell you HP means squat. He will ask you bob weight, rpm limit, and if it's a power adder motor. Mine runs a Molnar 4.500/2.200 crank and their 7.100 rods. Bob weight is 2222. Motor has a 7400 chip. Over 300 passes. Car has been 9.0#150@3350#.
Doug

I trust my builder (Tony Bischoff @ BES). I'm at 1060 hp with a 574 CI.

Glad to read this. I am pondering a whole new rotating assembly and was about to call molnar. Same deal; 4.5 stroke 7.10 rods. Would use a 7400 chip also.

My chip will be 8000. I run Oliver rods. I was trying to buy a Callies crank and that didn't go too good. Tony was not concerned with the Molnar crank.

In theory, the crank's stiffness (bending resistance) goes down with:
1.greater length (SB is stiffer than BB, other dims omitted, increased bore pitch)
2. longer stroke
3. reduced main or rod journal diameter (BBC rod journal)
When in doubt, larger radius at the journal edges helps.
I wrote some comments on journal overlap on my site: http://victorylibrary.com/mopar/journal.htm

My plan is to run a 4.375 stroke, with Oliver rods. Won’t be spinning it much over 7000.

Tom Molnar is quite happy to chat about t I am sure. He worked at Oliver before starting up on his own. Email him via his website or try contacting him directly on Facebook. Really knowlegable as you expect.

I run Molnar crank (4”) and rods (6”) in my small block.... only 246 passes on it though. Rod size considerably smaller than the Eagles we had in the W5 mill.

I have one for my 572 that is in the works. It should be an 850ish package shifting around 6800-7000.
Bought on the recommendation of others. I think I will be happy.

100% my experience when I asked about an HP limit on rods. Tom is the best!

If I was doing this combo I would use a Molnar crank and rods up to 900hp and 7500-7800rpm. Tom has put a LOT of R&D and analysis into his products. If you are wanting to make more power or turn more RPM I would use aluminum rods. They are WAY easier on everything else. R&R, BME or GRP are good choices. They will last 300 passes as long as they are heat soaked before the first pass and you don't motor down on them. All the OLD myths about aluminum rods are just that. MYTHS.

300 passes was Bill Jenkins' limit as well

I am surprised the rod manufacturers don't trust the general public with some accurate method of determining a life span of thier aluminum rods.
Some formula based on piston weight, piston speed and any other factor that has a mesurable affect on rod life would be great. There is a great deal of difference in actual life span between a pro stocker and a lawn mower!
Take for instance a motor i built back in 1986. 440 stock crank offset ground to 4 inch with a 2.100 sbc bearing. BME 396 forging rods made up with 7.15 c to c length. This motor never saw more than 6500 rpm and had a very light piston. I bet the life of those rods was(or is!) Thousands of runs due to low rpm, moderate stroke and light piston. I ran into the guy i sold that shortblock to about ten years later and he said it was still running great!

I bet the life of those rods was(or is!) Thousands of runs due to low rpm, moderate stroke and light piston

Exactly