Hot Rods What's the advantage of a 400 SBC?

I am contemplating going to a 400 sbc a friend has one and I can get it cheap. What kind of performance can I expect? can I transfer heads from my 350 sbc on to it?

 

The 400 has a bigger bore potential than a 350 and the bigger the bore the better heads you can put on it. As for your 350 heads, they will fit, but you have to have a machine shop to drill the steam holes in the heads to match the 400 block. The holes have to be extremely accurately places. If someone is talanted and knows what they are doing they can do their own steam holes, but I don't recommend it. Do NOT run a 400 without the steam hoes in the head. The only disadvantage to a 400 is you must have a very good cooling system so they do not overheat. JB2wheeler

 

That purty much sums it up. 400 sbc, baddest small block ever made.

 

no replacement for displacement.....thats the advantage......and yeah, the steam holes are very important, ran a bunch of 400s, never had any cooling issues though, but hey......

 

I've had one 400 and even when it was pretty tired it still had more power than the fresh 350 that I replaced it with. Good torque with it. That was in a 77 Chev one ton 4x4 crew cab that I did a lot of heavy hauling and towing with.
The big rub is that the Siamese cylinders do tend to run a bit hotter than the other small blocks but a good cooling system should handle that.
Any of the power tricks you would do to a 383 stroker should work just as well with a 400.

 

You can use a 400 specific head gasket as a template to drill the two steam holes in heads.Just be careful. done it myself and its not that tough to do.The best street small block.

 

Pokey
I've got two of them and have been a fan of them since I got my first one 22 years ago. They produce awsome torque, and will respond well to the traditional hop ups.
In stock trim they were never given the chance to breath (smallish cam, and undersize induction) so a proper rpm range cam (1000 to 5000) and a 4bbl and you will have a stout power plant. Don't tryto rev it like other small blocks it will not like it, so back off on rear gear (3.73ish you dont need more you now have torque) to keep it in it's rpm range. Those 350 heads depending on cc's may really jack up your compresion ratio pretty high so be careful (most 400s came with deacent flowing 76cc heads).
As jb2wheeler sais be serious about your cooling system.
Do it up I think you will like it.
Scott

 

As I recall torque.
I never had any trouble with cooling with mine.
Remember it is externally balanced, and requires some 400ci. specific parts.

 

The reason I use the 400 block is a lot more room for big valves.

 

I love them. I run one in my O.T. car. 330 hp/ 360 tq at the wheels. Fun, Fun, Fun.Even if you don't build it, at least save the block from the scrap heap. The 400 is getting rare. I've never had a cooling issue...I've spent good money to keep that from happening. Plan your cooling system before you build one and don't cheap out!

 

There really isn't an "advantage" of a 400 over a 350....other than cubic inches. More torque i suppose....
2 bolt 400 blocks are stronger than 4 bolt blocks...more meat around the webs....
400's have higher piston speeds due to longer rods and it's stroke, but unless it's an all out race engine, it's of no real concern.....

If it's cheap, grab it.

 

super engines, have one in my "go fast" car, not hard to get 450+/horses on pump gas.

 

400 + .030 = 406. Mmmm...tasty!

 

G'day. There are 3 different casting numbers found in the 400 sbc. The 511 was the early block and the majority of them were 4 bolts and quite strong. You can tell tWhem from the other blocks as they had 3 frost plugs per side. The next block they came out with is the 509 casting. These are the weakest of the 400 blocks and I avoid them like the plague. The final casting was the 817 block. This is the one found in 78 through 80 gm trucks. This block is the strongest of the three. It has a higher tin and nickel content and actually weighs slightly more than the other two. We have converted the 817 to splayed main caps and with steel cranks and better rods have routinely run them to 7500 rpms. Tons of torque and lots of fun.

ms

 

patman, that is tasty!!!

 

I ran a 377 for a while, 10.7:1 sportsman II heads. no cooling issues. But I didn't know how to set a tv cable, so I tore up alot of transmissions. Now that I have the internet, I wish I still had it.

 

If you are running rods longer thgan the 5.5 stock 400 rods be sure to select a cam that is ground with additional clearance.. also some times when running the 5.7 5.85 or 6 inch rod some grinding will need to be done on the bottom of the clys for con rod clearance. I got my first in 75 it had a 3 inch stroke and a bore of 4.155. our circle tracks had a stroke rule. these blocks are hard to find and expensive. of the last 4 I obtained 2 have come from running and driving cars. The last 2 bare 2 bolt units I paid $375 and $425 .. Have fun Bobby..

 

Cylinders are siameze and do not pass water between them. This will produce cooling issues.

 

Evening all... the 400 is a great motor especially for street use. It has the power where you really need it. As far as overheating goes, make sure you have a good cooling system and you should be fine. The one thing I would watch out for is that the 400 is externally balanced meaning it has a special torque converter and flywheel. Apparently GM didn't want to go to all the extra effort of adding extra weight to the crank to offset those big ol' pistons spinning around. But again, I think it is a great motor, I wouldn't have any hesitation of using one.

 

Special flexplate and balancer YES
special torque converter NO

 

I had one in a '72 Caprice Classic. I installed a 350 4-bbl iron intake on with a Q-jet... It ran pretty good for a stocker. Got the intake and carb for free. All it cost me was a little bit of time and some intake gaskets..

 

I want to say that the early 400's, '70 to say '72 or so, are all 4-bolt main blocks but I may be off here??

Some of the 400's only have 2 freeze plugs per side.

Some of them also have stock, 1.94"/1.60" valve heads, so check your heads here.

I drilled my heads by using a stock 400 headgasket as a template and two drill bits the same size as the block dowels to line them up right. I want to say one row of holes use like a 7/32" bit and the other side, something like a 3/32" bit. You should be able to hunt up a pic on the web that show's how to drill them. One side goes straight down and the other side outward, like at a 30 to maybe a 45 degree angle so as to miss the internal heavier casting sections. This is way easy to do!

And while you are at it, pin the rocker studs with 1/8" diameter x 1" long roll pins!

I have three, my ready to run, Strong-Arm 406, a complete apart one and a shortblock out in my garage.

pdq67

 

I just built a 406. The steam holes aren't that big of a deal to drill,I had to. The 400 heads crack in between the upper steam holes and the head bolt holes. You definatly need a good cooling system to prevent this

 

have one in my 68 chevy p/u....and yes external ballance. I used a 454 flex plate...already had the harmonic balancer..its a runner...I do have to make sure it has water, it doesnt like the 110*plus days we have here

 

I was hoping that the aftermarket had heads and intake I could just bolt on. Will I need a special starter as well. I like the sound of the thumper cam maybe I could get a package put together so I could have it installed by spring.

 

I ran one for two years in the street class at our local drag strip back in the early 90's. Flat tops, 202 double hump heads, mild cam, 2200 stall converter, TH 350, 373 posi. I could shift it at 5800 or put it in drive and let the governer shift it at 5000 and it ran the same ET. Never had to work on it. Fun motor. Keep it cool and dont over rev it.

 

You won't be needing a special starter.

 

My 4100lb bucket has ran 12.19 with a mild 406. no cooling issues ever.

 

I got one in my 47 ford ratchero and it it pulls like it did in the truck I pulled out of I'll real happy.I'll let you all know when I get it done.

 

got one in my motor home. torque monster. as for overheating... I have a factory oil cooler and a huge radiator, it goes to 180 and never moves above that. drove that sucker to Paso about 3 hrs each way for 6 or 7 years in a row in the summer heat and never had a problem. maybe people should say they don't like it IF they get hot, not that they are prone to overheating.

I'd like to have that motor in a car. I'm sure even stock they would scoot right along.