Join Date: Apr 2000
Location: Columbus, OH, USA
400's are awesome engines, I am building up one now. However they are more expensive to build up the bottom end by far, and the blocks are a lot harder to come by. I know a guy here in Ohio that has one that he's selling for $200 ready to go .040 if you live anywhere near...
If you are on a budget of less than 2 grand for the whole engine, you are in trouble, go with a 350... Also, I know Speedomotive sells kits to stroke a 350 up to a 391, but if you have a 300ZX or whatever, you will want a shorter stroke engine. The potential for that car with even a 350 is incredible.
If you are on a budget, find a short block 400 or complete engine that needs rebuilt, expect to pay $400-$500 unless you're lucky, use the stock crank and rods, trash the stock heads, but be sure to drill 400 steam holes in the new heads (search for older 400 posts about this). If you want to do it really well then use the longer and far superior 5.7" 350 rods. They just need a little clearancing to fit. and if you're doing this BE SURE to use 76cc heads becuse if you don't and you want any where near streetable compression ratio, your piston selection is minimal ($$$).
If you have a good donor engine for parts now you can build something killer for under $2,000. Use the 350 crank or go to Speedomotive.com and look at their stroker/destroker kits, some are really reasonably priced. The whole rotating assembly.
If you only are pushing 2300 lbs, the 400 itself is pretty light, you will have lotsa torque from the 377 cubes as is...
with 400's, if you are building a high rpm high hp engine try to stick with the 2 bolt blocks as opposed to the 4 bolt blocks. the 4 bolts aren't splayed main bolts, they go straight into the material between the clylinders instead of the two outside bolts going outward at 18 degrees. This causes them to crack easier there. And the longer rods (5.7) put less stress on the outside cylinder walls. I know a guy who said he ran 2 stock 400 short blocks and cracked both on the outside cylinder wall up the block vertically... Never heard this happening anywhere else but him. Also, the higher nickle and tin alloy blocks are stronger and can be distinguished by the casting numbers 010 and 020 under the timing chain. An 010 block will have tin in the alloy while the blocks with both numbers, 010 and 020, will have tin and nickle in the alloy. The nickle blocks are said to be the strongest of the 2 bolt blocks.
And of course install a Milodon 4 bolt main stud conversion kit if you are pushing serious hp. If under 475 the stock 2 bolts may be okay.
You will need a good 3 or 4 core radiator and be sure to hot tank the block really well to clean out the water jackets. I know there are a lot of other tricks out there to make the hot running 400's cool a lot better, like drilling an extra coolant hole in the deck and heads, and plugging up one of the two steam holes or something of that nature. Lots of weird mods to do to the block. Check out Lingenfelter's book on modifing Chevy small blocks, they discuss 400 head and block prep really well in there.
That's it for now, I have lots more 400 info if you need it. Check out Speedomotive's kits.
78 Camaro Z28 clone - 350hp/460ft/lbs 400 small block / TH350,
full poly suspension, 2" lowered, 1-1/4" & 1-1/8" sway bars