I'm going to be ordering a Dart Little M 400 block pretty soon and the block comes machined ready for a finish hone in either a 4.000 or 4.125 bore. My concern is lets say I order the block with a 4.125 bore and order 4.125 pistons. Who's to say when I take it to the shop to do the final hone that the cylinders won't already be too big for the pistons? I'm sure this would never happen but I've never bought a brand new ready to go block before and I know for a performance build you want to bore/hone and test fit each piston in its own hole, not just bore, hone and drop them in and hope its close enough. If I buy a 4.000 block and have it bored to match the pistons obviously thats going to add to the machine cost of the build but it would be a sure fire way to know the block will not be bored too big. Or is this taken into account with the pre machining of the block and this will never be an issue?

 

Just don't get the pistons until you mic the block. It should have no problem coming in @4.125'' tho.

 

I would think that a reputable company selling pre-machined blocks would account for the final hone in the specs, leaving the last few thousanths of an inch in play for it. But, it your worried about it, i would thing the best place to go would be the company.

 

I would think so too but being that this is the first block I will have ever bought I want to know what I'm getting into. I may end up calling Dart and seeing if they can get me an exact bore size as shipped.

 

Do you know who you are going to be purchasing it through? They might offer an assembled deal that is hard to beat. The original little M's come under 4.125, and have to be bored to get there (well thats what I was told when I got mine). I would call and see if you can get a deal on an assembled short block. And if you are maticulous about ring gap like I am, you could have them sent seperately and gap them yourself. I ended up going with a 4.155 the first time, and when I bought the turbo pistons I got them for a 4.165 (just a .010 hone). The guy that did the machine works said I didn't have to, but I had already bought the pistons. They have a lot of meat in them, they arent like a stock 400 block at all. I actually think they are about 80 lbs heavier.

If you are going with a radical setup, you might even want to consider a raised deck block. The cam is higher so you dont need to run a small based circle if your rods are close (when mine was a 434, the rods almost hit, I ended up with a small base circle), then you need to get lifters for a small base circle so they are lubricated properly. just a couple things to think about if you are starting from scratch. I really liked the 434, but I couldnt go that route with turbos because they dont offer a big enough compression height with a 6.00 rod unless you get a raised deck.

 

I want to stay with 400 cubes. I don't see the point in spending this much money on a block and then machining it away. With boost I want to keep as much meat in the block as I can. I thought about an assembled short block but I'm so **** about what I want I don't think I can do it. I want a Callies crank and rods and Wiseco forged 4032 pistons and would really prefer to assemble it myself. Flatlander Racing has the bare 400 dart little M block for 2300, about 400 less than places like Jegs and Summit. Speedway Motors has them for 2350 but not the exact part number I want. I'm pretty sure I want to go with a 400 main 4.125 bore block. Seems to me like you would want the larger diameter bearings to help distribute the load across the larger bearing surface would you not?

 

buy experience (doing bout 2-5 dart big m and little m blocks a week) dart little m 4.125 bore size blocks with billet or nodular caps need to be align hone fitted and bore size fitted. they are usuallly .0005" small on the align hone after properlly torquing with arp lube and the bore size is usually .008" small and has no cross hatch finish just a boring bar finish which will not work period. you WILL need to have the block align honed and bore fitted with a finish proper for your moly rings. everything should be measured @ 70* f..... for every 10*f variance expect .0001" difference in size give or take. a machine shop will take care of what you need. if you need pricing and machine work done call below...

Good luck
Ben Hardy
Cropper Racing Engines
Flemingsburg, Ky
606-845-4200