I have an 87 IROC with a 305 tpi that i would like to replace with a 400 small block, preferably a 4-bolt main. I'm not looking for a complete engine, but rather just a block to rebuild. I was wondering if anyone out there would know where I could get one for a reasonable price. There are a few out there that are priced good, but they want local-pickup only and the location is far away, or the shipping costs are ridiculous. I live in the Pittsburg area, and would be willing to travel about, say, 125 miles to pick it up. Any help would be greatly appreciated!

 

Buddy of mine in Cleveland, Oklahoma has one I'm sure he'd just give to you. He wanted to give it to me. It's a confirmed 400, 4 bolt main, block only.

 

You don't want a 4 bolt 400 block. The webbing is thin to accommodate the extra 2 bolts. You're better off with a 2 bolt casting and installing main studs for extra strength.

You need to find a 509 casting 400.
Stay away from the 511 and 817 castings.

For a basic street engine, any casting will do fine but chances are you want a 400 to make more HP so you might as well start with a good block. You also need to find one that still has the original bore. If it's been bored out once, there's a good chance it won't take another oversize. Pushing them to 0.040" over makes thin cylinder walls.

 

So you're saying a 2-bolt with main studs and right casting is stronger than the 4-bolt in general? I was told that getting a 2-bolt 400 would only be stronger if it was converted to a 4-bolt (which I can't do because the machine shop wants $1200 to do so and I simply can't afford it). You're correct that i want to build it for HP, but for the time being i will build it to about 425-475 HP. How much HP do you think a 2-bolt with main studs can handle?

 

The 4 bolt 400 blocks are weak castings because the webbing where the bolts are is too thin and can easily crack. The 2 bolt blocks have a lot more metal in the webbing. Studding a 2 bolt block is just as strong as a 4 bolt block.

There are always power limits with OEM castings. Never expect it to last if you're going to make serious HP. When you consider how much machine work is required to make a block ready for assembly, an aftermarket block can be a very good investment. $1200 for to 4 bolt a block is roughly half the cost of a good race block. Add in boring out the cylinders, line hone, decking etc and the cost to prep an OEM block can be very expensive and you still have a weak OEM block. That's also providing you can still find an untouched 400 block since they haven't been produced since 1979.

I think my last machine shop bill to do all the machine work and assemble the short block was around $2800. I supplied all the parts. Doesn't matter if it's a BBC or SBC, cost of machine work is the same.

 

Never buy any block that has bored and doesn't come with pistons.Virgin blocks on 400's is hard to find.The bucket list for 400's is sonic check for wall thickness,mag for cracks,bore/hone using torque plates with the intended pistons in the hands of the machine shop.The torque plates is critical performance or not because of the thin walls of the 400's it is likely you could have a 400 bored that wasn't cracked that will not seal.Worst is one bored with out pistons than trying to find pistons the right size to a finished bore size and not knowing if to that point the torque plates where used at all.

In the aftermarket blocks there are very good reasons why so many are used today.Aside from the thicker walls,the decks are also much thicker too just to name acouple.Also aside from the standard aftermarket blocks,there are options you can get with raised cam bore locations and cam bearing sizes that are the size of a BBC cam bearing.These aftermarket blocks target all the shortcomings of the OEM blocks.

 

I've seen a 2bm 400 sbc and a 4bm 400 sbc side-by-side, you want the 2bm.
I've seen a 2bm converted to splayed 4bm, short-filled, bored 60 over, and serve as a 580-HP daily driver for over 61,000 miles with weekend drags on another 150-horse hit of spray. And that was on a stock cast crank. A nitrous backfire killed that engine, broke the crank into 3 pieces. I was at the track when it broke, and I was there in the shop during the teardown.
The cylinders didn't fail. Dunno what the casting number was, or what year the block was. And it had those deck cracks from the steam holes even before the build. I was a teen when it went together, but I remember it well. It was not O-ringed, nor were there any lock-wire head gaskets from Fel-Pro back then. But it had ARP studs throughout, early-'70s 350 rods with ARPs, and TRW forged pistons. The heads were Brodix, because back then, all the serious guys with limited money used Brodix and those heavy old TRW forgings. There weren't that many options. That was the late '80s when it was built. Sportsman iron 200cc heads were too new to be trusted.
These days a 383 will get you close enough, at a lower cost. And better to use a Pacific-rim cast-steel crank than a GM cast-iron.

 

Cost to build a 383 and a 406 is identical.

 

We have used OEM 400 blocks of various sizes for 9.90 racing with the best prep machining there is and block filler.With leakdown tests being a common thread for all of them,the tests showed those engine's test results to be all over the map.They don't seal consistently and the bores do move around abunch.The other thing is I do agree with using a two bolt main block being stronger,but by the time you invest in splayed aftermarket caps and the required machining,your pushing the costs close to buying a aftermarket block anyways.