I was wondering at what point do you add new mains in a 440 motor? Looking to put a Source 512 kit in my 440, is it necessary to add new aftermarket main caps? I know its a good idea to have them but do you really need to. Thinking Compression will be around 12.36 to 12.00 depending on the heads I use.

You might want to move this to the race section. I would say it depends on rpm. Keep it under 6000 and stock caps should be OK. Main studs with a line hone would be extra insurance. Approaching 7000 rpm and steel/aluminum main caps are suggested.

Adding aluminum mains can be an expensive proposition as almost are bored for LB motors which have smaller mains (the 440Source ones are). This means they need to be align "bored" before align honing. Finding someone to do that is not as simple as finding a shop that does align honing. They also will likely need to be milled slightly to fit the registers so again you need a shop with a mill. If you're pushing this motor to its upper limits all the time or if money is no object then you should probably go for it, otherwise stick with the stock caps and studs.

Having just done a 440 based stroker I can tell you that in hindsight I should have done it with a 400-based block - you have bigger bores to start with so don't have to overbore as much to achieve the same c.i. and the aluminum caps can be installed with less hassle. Not to mention the weight savings! And 400 blocks have better support in the main webs.

A 12:1 512 sounds like a pretty stout engine. I think it would benefit from better main caps. Aluminum is supposed to be the best as it absorbs shock... although many (me included) run steel.

My opinion, if your making around 650-750 HP?
Below 650, you should be able to use the stock caps.
Above 750, the money would be better spent going towards a race block.

Chaz, get the aluminum caps and studs from Best Machine. He can line bore it to Mark

my , change the caps at 600-650 magazine horsepower. real world, i think 550 is max. i've seen the caps jumping around at less than 550. differing opinions here but i don't think the "b" engine bottom end is that strong.

So what your saying is it would be best to do a 400 to 512 than a 440 to 512? If thats the case i need to find a 400 in a good year and sell my .030 over 440 then.

Pic of my 4.15" stroked 400 (500 cid) with the BCR Aluminum Main caps and girdle:

Ok what is the best year 400 block should I look for and is there any to stay away from?

Anyone???

The most desirable block to start with would be the "71 230 casting WITH the thicker main webbing (not all 230 castings have this). However, any 400 that sonic checks good is a decent starting point. A partial fill, studded mains with aluminum caps, and a girdle should make for a pretty stout platform.

BTW: if your asking questions like this now, invest in Andy F's book, How to build Max Performance Mopar big blocks. He goes over all this and more, and he's a moparts member here, so its supporting a friend