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400 sbc

87 Blue Beast

87 Blue Beast

1/2 ton status
Joined
Feb 18, 2007
Posts
634
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Location
York, Pa
i have a few questions about the 400 small block since im thinking about building one. first off, i know everyone says that the 2 bolt mains are actually stronger than the 4 bolt blocks. this is true right? then i also heard that the 2 bolt blocks are only better if you machine them out to except the 4 bolt caps? i dont want to have to deal with the machine work to make the 4 bolt caps fit the 2 bolt block. so all in all, is the 2 bolt block with 2 bolt caps still stronger than the 4 bolt block? ive heard that the stock block will take 400hp easy. if thats right, then ill be fine. thanks guys
 
You heard right, but with only one variation.

The stock 4 bolt blocks are weaker than the 2 bolts because they take out more material for the bolts/studs, hence the reason a 2 bolt is stronger because there is more material surrounding it.

Now when someone says to machine a 2 bolt to accept 4 bolt, it won't be stronger UNLESS you use SPLAYED pattern. Instead of the stock position of the 4 bolts going straight down, the SPLAYED goes out at an angle. This allows the block to remain strong as the 2 bolt because there is still more material around the 2 main bolts than the stock 4 bolt design. The load is spread out more evenly with a splayed design than the stock 4 bolt design.
 
If your not going crazy HP wise, a 2 bolt or 4 bolt 400 mains will be fine. Where the webbing is on the 2 bolts blocks, there is more meat than a 4 bolt block. I had a 454 stock 2 bolt with 550 horse, no problems here.
 
ok, something else i forgot to ask about. im thinkin about trying to keep the tbi setup on my truck. i found a 50mm 750cfm tb that is a plug in/bolt on for these trucks. would it be worth it or should i go carb'd? how hard would it be to tune if i kept the tbi? i would like to try to keep it because people pay good money for fi, so why pay money to get rid of it?
 
It matters what powers the Injectors, as the factor 400s never had inj. A Holley Projection or other aftermarket kit is probably the best way to go. Then you tune with the knobs on the box on the fly.

A factory setup with prom would need some money thrown at it to make it work. The factory injectors are built to spec for engine size.

Any particular reason for not using a 350? all the factory inj stuff will bolt up, cheap.
 
i have a tbi 350 in my truck now. i wanted to use that setup on the built motor. im using a 400 cause i like how they run and i got the block for free :D
 
It's going to take more money than you think to keep FI on the 400. You will need larger injectors, a chip and the proper cam selection for the 400CI engine that is computer friendly. If you decide to use the 400 block then make sure that you have a shop magnaflux the lifter valley area REAL good. I haven't seen one yet that wasn't cracked there. Also the 2 bolt/4 bolt debate about which is stronger, the 4 bolt is stronger for the intended purpose. Who cares about the webbing "possibly" being thicker on the 2 bolt block, it's the force of the crankshaft downward on higher HP that is needed to keep the crank held up into the block. A 4 bolt block has more holding force than a 2 bolt block.
 
the 2 bolt block is deffinatly stronger. theres question. i already found out. i talked to a couple machine shop owners, one being a shop that builds sprint car motors, and they all said the 2 bolt block is stronger because there is more material where the bolts/studs go into on the block. they 4 bolt block has a tendency to crack around/between the bolt holes in the block because of the lack of material. after all, most race motors and all the sprint motors that this guy builds are all 2 bolt blocks :wink1:
 
You'll want to listen to 4X4HIGH, he knows his stuff. I've called him on the phone quite a few times to ask him motor questions and he's never given me a wrong answer or steered me wrong.
 
i dono man, im just tellin you what these guys told me. if acouple different people told me the same thing, its pretty convincing. so for, your the only person that has said that about the 400s. i really dont know.. all i know is i got a free 400 block, rods, pistons, main caps, pretty much everything but the crank for free, and im only planning on like 400 ish hp so i know ill be fine with a 2 bolt block.
 
I know I've mentioned this before on this board bout the TBI 406 that I built for my old truck.

400 4 bolt block, 30 over. Basic bore/hone, nothing special.
Stock 400 crank, new flexplate and balancer, stock replacement.
5.7" rods, stock out of something. ARP studs.
KB hyperuetectic pistons, IIRC 22cc dish
Whole rotating assembly balanced.
Comp Cams Xtreme Energy 268 cam/lifters.

STOCK heads, rebuilt with the steam holes.
STOCK intake
STOCK TBI (did have new injectors)
STOCK ECM

Nothing done to any of it. The motor ran friggin' awesome. Would idle all day long, (nice choppy one too) had torque to smolder the tires off at will.
Still get about 20 mpg on the highway. I never had it dyno'd, but a WAG at 350 horse, and 400 ft/lb torque. The truck never had any problems overheating, check engine light never came on. I wish I kept the truck.
 
I used to be heavy into the dirt track scene. All the guys I knew ran the 2 bolt 400 blocks. Whether they are stronger or not, I don't know. I DO know they would run those 400s 5-6K steady, with spikes from the bumpy dirt tracks, and never saw one come apart.
 
The biggest reason people run the 2 bolt 400's are they are WAY easier to find than a 4 bolt 400.
 
87 Blue Beast said:
i dono man, im just tellin you what these guys told me. if acouple different people told me the same thing, its pretty convincing. so for, your the only person that has said that about the 400s. i really dont know.. all i know is i got a free 400 block, rods, pistons, main caps, pretty much everything but the crank for free, and im only planning on like 400 ish hp so i know ill be fine with a 2 bolt block.
Click to expand...
Theres a difference between listening to what other guys tell you and what a guy with 21 years of machining service has to say.

Its like Tommy Boy said in the movie, "You can get a good look at a T-bone steak by sticking your head up a bulls ass. But I'd rather take the butchers word for it instead."

Consider Scott (4x4HIGH) to be the butcher for you. :wink1: :bow:
 
4X4HIGH said:
The biggest reason people run the 2 bolt 400's are they are WAY easier to find than a 4 bolt 400.
Click to expand...
The guys I raced with, would TRADE a 4 bolt for a 2 bolt. Back in the 80s, seems like there were alot more 4 bolt blocks around, than 2 bolt blocks.

I know there is a noticable difference in the thickness of the main webs. Personally, I think either set up will hold up just fine.
 
how about the stock 400 rods.. how much power will they take safely after being shot peened, de-burred, arp studs and fully balanced? also, what about the heads? what will happen if i use aftermarket heads without the steam holes?
 
Forget about the stock 400 rods, they are too short at 5.565" instead buy or gather up a set of 5.7" 350 rods.

No steam holes means instant overheat issues.
 
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