Aluminum Main Cap Usage

I have a question concerning aluminum main cap usage. Will aluminum caps survive (Longevity) on a 600 hp street motor? Occasional strip but mostly street and lengthy (out of state) highway trips. Or would it even matter for my intended usage? All this talk about cap walk, harmonics and aluminum caps absorbing a lot of stress of a high performance setup have me thinking overtime.

Yes they will be fine in a street strip car. I did a 451 years and years ago with aluminum caps. Car is still street driven now as well as the occasional race pass. When I sold it 16 years ago it logged 5500 street miles and 120 laps at the track running mid 10's in a 65 Belvedere and still does.

I have no doubt they'd be fine, but they're a waste of money for your application IMO.

OP, if you keep the motor in a good state of tune with no detonation, especially at WOT, you won't have main cap issues at that HP level.
Let it detonate a little or a lot and you will

Cab, at what point would it be a good idea to change to ductile caps?

You likely already have ductile caps 😉

I haven't found any one now making Ductile iron caps any more. Mopar stopped making and selling them and Milidon doesn't offer them either any more
Milidon does offer steel caps, so does 440 Source, but I'm leery of using steel caps on a cast grey iron block
I have one of the Koleno high nickel blocks that I am planning on using soon for all out N/A build, hopefully the main caps on it will work for my power level
I wish Dart, Brodix or some other good quality manufacturer would make a good Mopar V8 race block out of cast Compact Grey Iron like they do for our competition in the Chevy and Ford camps

According to their website, Milodon still offers ductile iron caps.
Milodon caps

I saw that on their website also last year, according to Tom they don't have them anymore when I called to order several sets, just steel now

You are overthinking it. Put some ARP main studs in it, have the shop torque them to spec and then line hone it and call it good. Save your money for something that matters.

What block are you wanting to use?

Huh, why list them as ductile? Summit and Jegs have them listed as ductile. I wonder how many have been purchased under that assumption?

You dont need aluminum caps. Stud it, align hone it properly, balance the rotating assembly correctly, and tune it. Yours is simply not an application where it really benefits from it. Good luck.

Been using stock caps with ARP studs on 600 HP street engines. On a street engine, your not normally at WOT all the time anyway. Save the money you would have spent on caps and get a light weight rotating assembly that will take strain off the block and caps.

Thanks for all the advise everyone. With all the different ways and opinions to build a mouse trap I do tend to overthink the available options.

It is way better to be careful on engine builds than not

My 440/493 has been in my car running fine since June 2011 and I used 440Source billet steel main caps with ARP main studs and that's all with a main cap align bore of course. Mine is a street car that only gets raced once or twice a year. Its held up great as I have had no problems at all with it and it will run 10.70's best in full street trim. I agree aluminum caps will work fine but they are not needed for your application. Good luck with it , Ron