I've waited over a year for the Milodon ductile iron 4 bolt main cap setup. Now pushed to June. I'm looking for a new path forward for an oem iron block 440RB block stroker.

Can I use aluminum main caps (I've read the advantages from search past posts on main caps) without having to take the motor out and tear it down regularly? Or can I use billet steel main caps perhaps with a girdle (not looking to use BCR as don't want to have to consider shimming motor mounts, extending pickup, etc) with a steel rod 508" stroker with ~600 HP? From my reading I'd go with ductile iron main caps if I could find any new. And have been advised to use billet steel versus aluminum to not have to service motor/bearings regularly. I've got 99% of parts and ready to get to a machine shop... Thanks.

I don't think 600 HP warrants anything other than stock caps. Just my opinion.

The only stock 440 block I ever cracked had 440source steel caps on.

Not sure why you’d have to service the bearings more than usual with aluminum main caps? Some manufacturers use iron blocks with aluminum mains. Cadillac did this IIRC.

x2

OK. But if I don't have the factory main caps and only steel billet or Aluminum appear to be available new, what do I go with?

There's a set of factory main caps for sale in the "Moparts Engines" section.

You can’t go wrong with aluminum. Monte recommended that to everyone on this site years ago while he was living.

If your going to replace them don't use steel The harmonics from cap walk will crack the main webbing and you won't know it until that block fails
Aluminum caps don't do that is what I have seen so far
Your better bet is to find a good race block or a good 400 block withe thicker main webbing and build it with good caps and so on, they tak ea lot more power and punishment than any stock 440 production car block made to date

I fitted my 650rwhp street/strip motor with a BCR cap & girdle kit 8 years ago. This engine is still taking the beatings on a regular basis. I did however add bushed lifter bores so oil pressure never drops below 20psi at idle when hot lapping her. This combo hasn't been apart except for some head work in that 8 years. I've built a few strokers before, but none have lasted this long without having an issue to require a rebuild. I put it down to the quality girdle combo & the bushed lifters, money well spent, no junk parts.

Thanks for the great info. What car did it go in, a B body by any chance? Was it a 440RB block? Did you have to space your motor mounts or extend your pickup tube?

Yeah, but will aluminum main caps make regular inspection and maintenance of possible pulling the motor a requirement? I'm looking to be able to install the motor and not have to pull it out again until it's tired out. Which with the limited driving miles I'll do should be beyond my likely lifetime.

I'm not sure why either. Just that from what I've read on this subject it would appear that most that are using aluminum caps appear to pull their motors regularly, being more track than street/strip cars. And at least one engine builder told me to not go with aluminum for street use as they won't last.

I believe 600 will be on the low estimate. And I do have a NOS system, which I'd likely not be brave enough to use again no matter what main caps.

At 600 hp, the stock caps will be fine. If I were going through the expense of installing new caps, they'd be aluminum.

x3 (with ARP studs)

If you get the tune wrong, especially with nitrous, no main caps are going to help you. Aluminum caps help dampen vibrations and reduce/prevent fretting and windmilling. Magnesium would be even better, but then you'd have a corrosion issue in that environment. S/F....Ken M

Dang ,dude I hope that didn't hurt you or the car

No, this was a customer motor. 440 based 512, 440-1's, Eagle rotating assembly as I recall. It had stickers from a rather widely known Mopar shop on it, the guy blew it up supposedly on his 1st weekend after getting it back. Based on the rust, I assume i was sitting for a bit, or maybe the shop just doesn't GAS enough to bead or shot blast parts.

I don't use stock main caps for anything other than stock headed builds. I don't build for other people, I just machine parts, but that's my 2 cents. S/F....Ken M