thinkin of swapping in a sb 400

[nu2u72]

hey guys, my truck (72` gmc ) has a late 70`s 350 in it right now which is nothing like the older motors power wise, so I`m thinking of swapping in a nicely rebuilt 400. Now just so you know I used to work in a engine shop where we built anything from stock to wild but that was many moons ago when I was 17 ( now 36 ) so I know how to rebuild an engine.
My question is. I`ve found a 400 2 bolt block here locally for a good price, so what do I need for a crank for this bad boy? does it have to be a 400 crank or will a 350 crank work? I`m not familiar with the 400 at all but know the 350 in and out. I know you can put any 350 head on it but you have to drill the steam holes, and i know the intake from any sbc will work.
I guess what i`m askin is what exactly do i need to look for to rebuil this motor? 6" rods or 5.7" rods? I`d like some power, like in the 350 to 400 hp range any of you guys build such a thing? I know it would be much easier to just find a whole 400 but they are not easy to come by around here.

help

[raycow]

400 main journals are larger than 350, so you can't just drop in a stock 350 crank. You would need to find some of the special thick bearings that used to be (maybe still are) made for this swap. A better fix would be to use an aftermarket crank.

Ray

[eldogg]

Eagle or Scat both make a affordable crank for your 400. Retails for around $200.00. Eagle does a internal balance crank for about $250-275. Thats only way to build a 400 in my opinion.
I have built a few 377's (400 block/350 crank) They make a killer nitrous motor but I wouldn't put one in a truck.
Good luck,
Eric

[nu2u72]

thanks guys! so tell me about this internal balancing. just like a 350 I take it? so the 400 was an externally balanced engine? flywheel and balancer? I would imagine the internal balancing would be the way to go for sure!
I`ll look more into this 400 block, from all the reading I did last night it looks like it`s exactly what I`m after. what about towing say a 5th wheel or my heavy ole boat? any heating issues? sounds like a myth?

thanks alot guys,
Ron

[leddzepp]

It is not a myth. 400 SBC's have a tendency to overheat in my experience. We always had issues pulling our boats/trailers. Went to a big block and never had a problem after that.

[vectorit]

400 SB's are siamesed bore blocks, that's why you need the steam holes in the heads. Problem I have had with these engines, is if it gets a little over normal operating temps the head gasket gives way at those holes. This happens more often when the cooling system is dirty, and the water jackets get sediment in them. Which causes the steam holes to fail at being affective.

When kept in tip top shape they are good motors.

My opinion on them, with first hand experience owning 4x4 Chevy's powered with the 400, 350, and the 327. The 400 to me seemed like a warm running thirsty 350, it wasn't spectacular to the point where I thought they were a must have.

If I was looking for a mil to drop in my truck to pull an RV, I'd go with a BBC before going with a 400 SBC.

JMTC

[BADPURPLE70CHEVY]

Originally Posted by vectorit

400 SB's are siamesed bore blocks, that's why you need the steam holes in the heads. Problem I have had with these engines, is if it gets a little over normal operating temps the head gasket gives way at those holes. This happens more often when the cooling system is dirty, and the water jackets get sediment in them. Which causes the steam holes to fail at being affective.

When kept in tip top shape they are good motors.

My opinion on them, with first hand experience owning 4x4 Chevy's powered with the 400, 350, and the 327. The 400 to me seemed like a warm running thirsty 350, it wasn't spectacular to the point where I thought they were a must have.

If I was looking for a mil to drop in my truck to pull an RV, I'd go with a BBC before going with a 400 SBC.

JMTC

Got a 406 and i have no cooling problems at all in heat. Member Big al has a 406 also and i know he leaves in extreme heat and has no problems. It all comes down to setup.

[GRX]

I disassembled & remachined a lot of sb 400's back in the day. There is a reason they aren't made any more. The more the miles, the more the cylinders will develop unusual wear patterns because of the siamese cylinders. If you want 400 cubes, go with a Pontiac.

[turp mcspray]

I built a 400 for my blazer and loved it. I know lots of people with 400s in everything from race cars to daily drivers. Nobody I know has had any bad experiances with them. A good friend of mine built one for his late 70's 3/4 ton tow rig. All he uses the truck for is towing. I have heard of them having heating problems, just like many other people have. I just haven't personally known anyone who has had problems. If I am going to build a small block, the 400 is MY first choice.