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Old 10-30-2017, 08:15 PM   #1
Coley
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SBC 400's cubic incher...any good?

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.

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Old 10-30-2017, 08:27 PM   #2
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Re: SBC 400's cubic incher...any good?

I ran a few 400 and really liked them, lots of torque and power.
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Old 10-30-2017, 08:41 PM   #3
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Re: SBC 400's cubic incher...any good?

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.
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Old 10-30-2017, 08:47 PM   #4
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Re: SBC 400's cubic incher...any good?

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.
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Old 10-30-2017, 08:49 PM   #5
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Re: SBC 400's cubic incher...any good?

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

Last edited by ho70; 10-31-2017 at 09:07 PM.
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Old 10-30-2017, 09:11 PM   #6
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Re: SBC 400's cubic incher...any good?

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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Old 10-30-2017, 09:11 PM   #7
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Re: SBC 400's cubic incher...any good?

Well as they say, there is no substitute for cubic inches. Bigger really is better.
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Old 10-30-2017, 09:18 PM   #8
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Re: SBC 400's cubic incher...any good?

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.
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Old 10-30-2017, 10:54 PM   #9
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Re: SBC 400's cubic incher...any good?

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
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Old 10-31-2017, 12:25 AM   #10
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Re: SBC 400's cubic incher...any good?

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.
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Old 10-31-2017, 12:37 AM   #11
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Re: SBC 400's cubic incher...any good?

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Originally Posted by special-K View Post
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!
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Old 10-31-2017, 01:50 AM   #12
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Re: SBC 400's cubic incher...any good?

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.
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Old 10-31-2017, 07:49 AM   #13
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Re: SBC 400's cubic incher...any good?

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.
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Old 10-31-2017, 10:10 AM   #14
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Re: SBC 400's cubic incher...any good?

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.
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Old 10-31-2017, 10:28 AM   #15
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Re: SBC 400's cubic incher...any good?

Quote:
Originally Posted by davischevy View Post
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.
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Old 10-31-2017, 10:55 AM   #16
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Re: SBC 400's cubic incher...any good?

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
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Old 10-31-2017, 10:55 AM   #17
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Re: SBC 400's cubic incher...any good?

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...
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Old 10-31-2017, 11:01 AM   #18
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Re: SBC 400's cubic incher...any good?

Dirt trackers around here used to love the 377. Higher tg and hp in the upper RPM. But I agree Davepl no replacement for displacement. If I were build another it would be 406.

But I am over that tiny stuff only BBC for me.
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Old 10-31-2017, 11:02 AM   #19
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Re: SBC 400's cubic incher...any good?

An incredible engine!!!
Revs like a small block, torques like a big block!!!

I hear folks talk about their stroker 350, being a 383.Why not use the 4.125 bore block, which helps unshroud the intake valve.....it does make a difference.

There's a bunch of wife's tales about the 400 block (my opinion, not here to bash anyone, such as post 3)
The steam holes DO have to be in what ever head you use. You DO have to keep the coolant clean. A torque plate needs to be used when honing the cylinders, especially with the siamesed bores.
My buddy had a 406 in his 66 C10, LWB, 2WD. THe engine was simple:
He used the cheapest forged Sealed Power pistons, and the short stock rods
Comp 268H High Energy cam NOT the XE grind!!!
Edelbraock Performer intake. This was one of the earlier versions with the bigger runners.
Holley 3310 750 Vac. sec. carb
1-1/2" primary tube headers, sounds like puny tube size, but they worked very well.
Factory 441 cast iron heads, that the engine builder massaged just a little, here, and there!
He had a Muncie M20 transmission with a 3.42 gear.

The build sounds VERY lame. It dyno'd 300 HP with 400 ft/lbs torque.

That pickup ran awesome!!!

Oh...almost forgot... I have a 406 on a stand waiting for my 67 C10, built by same builder. 390 HP 440 torque. I plan to run a TH400, 3.73 gear...
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Old 10-31-2017, 11:29 AM   #20
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Re: SBC 400's cubic incher...any good?

If anything in this world really NEEDS a 400 it is a square body 4wd Suburban, which just happens to be what I own. With the shortage of decent standard bore blocks I've been looking at the Dart block with the heavier casting. Will also accept a roller cam. Maybe at tax time I can afford it.
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Old 10-31-2017, 11:58 AM   #21
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Re: SBC 400's cubic incher...any good?

Quote:
Originally Posted by B. W. View Post
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
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Old 10-31-2017, 11:59 AM   #22
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Re: SBC 400's cubic incher...any good?

People destroke motors to get them to rev higher or to meet cubic inch requirements for racing. (SCCA on 70's hence the 302 dz Camaro motor). Also buy that 400 and use it, you aren't gonna lose money of a sbc 400-hens teeth category.
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Old 10-31-2017, 12:03 PM   #23
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Re: SBC 400's cubic incher...any good?

Quote:
Originally Posted by kwmech View Post
If anything in this world really NEEDS a 400 it is a square body 4wd Suburban, which just happens to be what I own. With the shortage of decent standard bore blocks I've been looking at the Dart block with the heavier casting. Will also accept a roller cam. Maybe at tax time I can afford it.
Very good thinking, there!!!
I don't know who all makes an aftermarket 400 block, but you wouldn't need anything too special. When a debate starts about which stock block to use, it gets blown out of proportion. As long as a stock block has no cracks (main bolt holes especially), it good for me. I wouldn't be Race'n it and no extreme RPM's for my use.

I'd likely buy the least expansive 400 aftermarket block I could buy....
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Old 10-31-2017, 12:29 PM   #24
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Re: SBC 400's cubic incher...any good?

Quote:
Originally Posted by Coley View Post
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.
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Old 10-31-2017, 12:45 PM   #25
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Re: SBC 400's cubic incher...any good?

I've been running a 406 in my 69 GMC for 20 years with no problems.
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