SBC 400's cubic incher...any good?

[Coley]

Just wondering what everyone thinks about the 400 sbc's (not the big blocks).
I know these were used in the early mid-70's on some bigger vehicles but were never a 'performance' engine to my knowledge.
Are these reasonable performers in these trucks? ....say with an updated intake, exhaust, etc?

....just wondering if anyone has had much experience....positive or negative with them.

All Good
Coley

[kwmech]

I ran a few 400 and really liked them, lots of torque and power.

[Steeveedee]

My dad had one in his '75 Caprice convertible. That pig weighed as much as a truck, but it moved it right down the road, smog equipment and all. Because the cylinders are so close together, I don't know how much you could bore one, if you found one that needed it. Note that the closeness of the cylinder holes ended up causing GM to drill steam holes in the block and heads. You can't use the gaskets that fit "all the other" SBCs. And if you get a head for it, better make sure that the holes are in it for the steam. I'd personally stay away from it, TBH. You want big power, get a BBC, and your work is done for you.

[truckster]

It's a great engine. Any head can work with it, including Vortec heads - you just need to drill the steam holes. I wouldn't hesitate to take one in good shape.

[ho70]

The came along when the smog emissions were mandated. The 400's could still get modest power with all the emission stuff. They were never high performance as they came to the game to late. A properly done 400sbc is a monster. IF you run the proper heads etc, cooling isn't an issue

[Boog]

Well as they say, there is no substitute for cubic inches. Bigger really is better.

[B. W.]

If you think about it, the 383 is a 400 with a smaller bore. If I had a choice between the two I'd run the 400.

[harpo231]

Originally Posted by B. W.

If you think about it, the 383 is a 400 with a smaller bore. If I had a choice between the two I'd run the 400.

Mine is 350 block and 400 crank

[garyd1961]

Originally Posted by B. W.

If you think about it, the 383 is a 400 with a smaller bore. If I had a choice between the two I'd run the 400.

Wrong, totally different blocks. The SBC 400 as someone has already said have problems with cooling. If you bore it out it has worse problems with cooling. I would go with a 350 block , you can always machine it and put a 383 crank in it if you want more cubes.

[truckster]

Originally Posted by garyd1961

Wrong, totally different blocks. The SBC 400 as someone has already said have problems with cooling. If you bore it out it has worse problems with cooling. I would go with a 350 block , you can always machine it and put a 383 crank in it if you want more cubes.

Plenty of 400 SBCs have run for decades without cooling problems. You need to have the steam holes in the heads and have a cooling system that works as it's supposed to.

[kwmech]

Originally Posted by garyd1961

Wrong, totally different blocks. The SBC 400 as someone has already said have problems with cooling. If you bore it out it has worse problems with cooling. I would go with a 350 block , you can always machine it and put a 383 crank in it if you want more cubes.

BUT, you cannot take out the 350 block to 4.125+. The only cooling problems I've really seen with a stock 400 is lack of maintenance with the cooling system. Dirty and partially plugged radiator immediately comes to mind. I've never had an overheat problem with any of the 400s I've had

[special-K]

Originally Posted by garyd1961

Wrong, totally different blocks. The SBC 400 as someone has already said have problems with cooling. If you bore it out it has worse problems with cooling. I would go with a 350 block , you can always machine it and put a 383 crank in it if you want more cubes.

Wrong. That 383 crank (and rods) is a 400 crank. He never said the blocks were the same. The comparison is in the rotating assembly. No need to bore one out since it's already 17 cubic inches bigger than a 383. Yeah yeah, if the motor wears and needs rebuilt one day they don't take over boring as well. But plenty running around not needing that and they don't run hot. I don't think a 350 block can take the 400's bore either. Isn't the 383 max bore in a 350 with 400 crank?

[Grandpas 72]

Hello everyone,
The 400 CI SBC is a great base to make lots of power and are popular with the drag racing community. I believe Chevrolet produced the 400 small block for 10 years. One issue with them is that they have Siamese bores meaning that the cylinder walls are solid between the bore center lines. Coolant can not pass between each cylinder and it only flows against the top and bottom of the bores. Because of this the cylinder walls can not cool evenly often creating a distortion. ( The bore becomes egg shaped) That's why they are popular with drag racers because the engines aren't ran for long periods of time. Lots of power can be made with these engines but it's important to keep an eye on the temp gauge.
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[special-K]

I love how thy move a truck. They have truck torque, feels effortless compared to a 350. Do people like 383s? Heck yes! That's just a 350 trying to be a 400. A 383 is what a 350 was supposed to be in a truck. I had both my '72 K2500 Sierra 350/TH350/4.10/33/12.50 tires and my '72 K/20 Highlander 400/4spd/4.10/35/12.50 tires and got same mileage (12.5 mpg) with the K/20 barely off idle cruising down the road. The 400SBC is so right in these trucks Chevy made an emblem for them

[davischevy]

I bought a new K10 Silverado SWB in 76 with a sb 400. I loved that engine.

I have a 377 (400 block/350 crank) with world products heads, in my 65 Chevelle. That is a good setup too. We ran that same engine on dirt tracks at one time.

[68is4me]

Originally Posted by davischevy

I bought a new K10 Silverado SWB in 76 with a sb 400. I loved that engine.

I have a 377 (400 block/350 crank) with world products heads, in my 65 Chevelle. That is a good setup too. We ran that same engine on dirt tracks at one time.

I also ran a 377 very strong motor.

I still have a few 400 sbc sitting in storage hoping someday they will be worth something. The best 400 blocks are the 2bolt mains. The 4 bolts were drilled into the cylinder webs and made them weaker so I have been told. But my 377 with factory 4bolt was close to 500hp, the valve knocked a hole in the piston and never had any bottom end problems.

[Ironangel]

Originally Posted by special-K

I love how they move a truck. The 400SBC is so right in these trucks Chevy made an emblem for them

Cant say it any better than this!

[KQQL IT]

Love all the 400 sb I've ever had. And abused them plenty.
Currently running a roller cam dart head hot rod.
Always run good.

[special-K]

I can't find any 400s around here. My buddy runs 406s in his 8 second Vega and has a nose for finding the 400s. He has a '71 Cheyenne Super that his old customer sold him when he went into a nursing home. He still had his house and would come home to drive it. But one day it came in on a rollback. Water pump went, fan tore radiator up, and 350 got way hot and Jeff bought it. He had it painted, built & slapped a 406 in, and a set of Torque Thrusts and has a great truck. He had one in his '68 C/10 before that...and everything else he's owned, it seems.

[DeadheadNM]

I bought my 72 GMC from the widow of the original owner: it was garage kept and maintained in all original condition. The owner used it to tow a fishing boat. She told me the motor had been replaced under a warranty claim not too long after being purchased but couldn't recall the details. I ran the suffix codes and it turns out a 400 sb was installed. Whoever did the swap did a great job as all the small pieces are there (oil dipstick is correct for 72 4wd for example). I love driving this GMC: the motor fires up quickly and just purrs. It's got nice torque and with the 3.73s moves quickly off the line.

[Coley]

There is some great feedback here....and it sounds pretty positive for these motors.
I know of one (1973 400 sbc) that I can get with 165psi compression (+/-5 all holes) for $400 that I have been considering.
It would be a temporary transplant for when I took my original (350) engine out and had it redone over the next year or so. No immediate need but just to have to 'keep going' while the other gets updated, etc....but again, there is no immediate need for this, which makes it only a consideration.
....still tho', its tempting.......hmmm.

All good
Coley

[truckster]

Originally Posted by Coley

There is some great feedback here....and it sounds pretty positive for these motors.
I know of one (1973 400 sbc) that I can get with 165psi compression (+/-5 all holes) for $400 that I have been considering.
It would be a temporary transplant for when I took my original (350) engine out and had it redone over the next year or so. No immediate need but just to have to 'keep going' while the other gets updated, etc....but again, there is no immediate need for this, which makes it only a consideration.
....still tho', its tempting.......hmmm.

All good
Coley

You wouldn't be disappointed with it. Just remember it's externally balanced, but everything else bolts up.

[Boog]

Originally Posted by truckster

You wouldn't be disappointed with it. Just remember it's externally balanced, but everything else bolts up.

Shoot. I’d leave the 350 in it while i freshen up that 400, swap em out and never look back.

[truckster]

Originally Posted by Boog

Shoot. I’d leave the 350 in it while i freshen up that 400, swap em out and never look back.

I would probably do the same.

[davepl]

One thing I've never been able to figure out though:

People take 400s and put 350 cranks in them and make 377s.
People take 350s and put 400 cranks in them and make 383s.

Why would the 377 be preferable over the 400? Why destroke it? I know it would improve the rod ratio, but in terms of perf, maybe piston dwell is different? I don't get it, like I said...