SB 400 motor

[lonestarjarhead]

Anyone out there with experience (good or bad) with SB 400 motors? Just starting to restore a 76 Sprint with factory SB400 and need to figure out whether to rebuild it or go another route. I like the idea of the cubic inches, but older mechanics around here say that it was the worst engine GM ever built (must be really bad to beat the Vega), and was prone to overheating. Must be good for something, though, 'cause I've had several dirt track racers wanting to buy my motor, if I swap it out. Any suggestions? Thanks.

[conquista90]

The 400 was a great engine. However, if there weren't any provisions for the steam holes that the heads required, yeah, it would overheat. Also, if the head gaskets covered them up it would overheat. And the 267 V8 was the worst V8 GM ever made. Period.

Keep the 400. If rebuilt right, it'll be an awesome engine. The guy who lives across the street from me has a Pontiac 400 that pushes over 750HP.

[toms84ss]

Chevy 400 and Pontiac 400 are like apples and oranges. Not even close to being the same. Chevy 400 has some drawbacks. As mentioned the head gaskets with steam holes need to be lined up. They also have siamesed cylinders. Meaning the water jacket does not go all the way around the cylinders. You need to make sure the cooling system is top shelf. Only other thing is the crappy short connecting rod. But with the 400 your stuck with it. Get a good cooling system, make sure the gaskets are in right and enjoy the extra torque of the 400.

[66trar]

Okay, I've been doing a TON of reading and talking with drag racers around my area. DONT GET RID OF THE BLOCK!!!! If you want serious power, keep it and forget the 383. Check this out:

http://www.chevyhiperformance.com/te...que/index.html

and this:

http://www.chevyhiperformance.com/te...ild/index.html

As long as your block is still standard bore and can be bored out, keep it and have it cleaned and mag checked for cracks.

As for any weaknesses of the block:

The cooling system is fine if you treat it right. get the right gaskets for a 400, ensure that they line up correctly with the block and heads and ensure that any heads you buy for it are properly drilled out for the holes to match. As for the short rods, yes, that did suck about those engines. Luckily for you and me, (I just purchased a 400 block that I'm gonna build up), you can buy sets from 5.7 inch rods up to 6 inch rods to make up for it, you'll just have to get a small base circle cam, (call the cam company to order this specifically, its not much extra) and some very minor clearancing, then it's problem solved. As for the siamesed cylinders, other than requiring steam holes, they're actually a good thing, they help the cylinders stay properly aligned and they don't move around as much as a non-siamesed setup does. Just check the specs on the GM rocket block, the World motown block and the Dart Little M block. They all have siamesed cylinders for this reason. One thing I've heard of though, on 400 blocks specifically, due to a few of the steam holes being closer to the head bolt holes, use studs on the heads. This will help prevent cracking in that area when the heads are torqued down.

Anyways, hope this helps! Those racers aren't wanting your block for nothing, 400s are getting scarce these days... I was VERY lucky to find mine.

[Steve81OR]

A friend of mine races a full size Chevy Van with a SBC 400 and it runs great. To compensate for the poor flowing heads he put factroy style Vortec heads on it, solved all his flow problems and gave him a good 20 - 40 HP boost.

Check out the complete heads at Summit, ready to bolt in.
Summit Link

[elcamino74guy]

If the block is sound definitely keep it. There really is no substitute for cubic inches and while it does have a relatively short stroke the bore (4.125) makes for a real torque monster.

I wouldn't rev it much past 5500 RPM unless you plan on a lot of bottom end strengthening though. The one characteristic shared with the Pontiac 350/400 and the Chevy 400 is that they're not meant for high revs for any length of time. They're a torque motor.

Better flowing heads, steam holes, better rods and a good cooling system and you'll be good to go. The rods are actually the weakest link in the motor.

Here's a link to a page that talks about relationships of ROD sizes and such
Connecting rods

It kind of backs up what I said about high RPM use.

[old_coot]

I have a small block 400 thats been punched .030 with dished forged pistons and four bolt mains thats going in my El Camino----its a fine engine as long as you know a few things about it----yes it has short rods stock but since you are doing a rebuild you can get pistons with the pin relocated and use longer rods---you will need a reduced radius cam---I'd go retro roller---and be aware of the steam holes between the heads and block---in addition to that, consider it a big block when choosing cooling system components--namely radiator.
The other things to consider are the drivetrain components, these engines can generate nearly 500 lb/ft of torque so the tranny and rear end needs to be able to handle it. I have a much modified th700r4 and am adapting a (blue oval) 8.8 inch rear out of a turbo t-bird for mine..........................Dan

[elcamino74guy]

BTW I meant short rod...

[turboapache3132]

The 400 small block is a great eng, but there are a few things you have to take into account. If the eng you have now is using the 5.56 rod you need to pay attention to the thrust side of the block. That short rod and long stroke creates a high angularity and high wear on the thrust side of the block. Do the rebuild with 5.7 rods and the correct pistons and you solve the problem and have a smoother motor. I run these engs all the time and they make awsome torque like 500 ft lb or more, and they make it from 2000 rpm on up to around 6000 if you have the right cam setup. A roller cam is a must along with 1.6 roller rockers, and a good set of heads like the AFR 195. These give plenty of flow and great velocity. .30 over gives you 406 cu in. Good luck and have great fun with the {little motor}

[r-59]

I was leary of the 400 due to the cooling stories, but I found one I could'nt pass up, the problem was it had a bore of .40 over cooling probs. for sure....right! ...wrong...did the heads right, put in a new big alum. rad..
(it's in a 59)the temp stays at 140, never over heats. runs a special crane cam,selected and designed by harvey himself, 60's style cross ram with 2 carters side byside. it did go through the origional 3 seed with overdrive and had to replace the old motor mounts,but now with the 5 speed, that old 4000 pound baby rises up in every gear, what fun to drive!....go for it

[84 G camino]

MY 400 HAS THE STOCK 350 RODS AND ARPS. COMP XE284. ALL I HAD TO DO FOR CLEARANCE WAS MOCK IT UP, TURN IT AND GRIND (SLIGHTLY) 2 ROD BOLTS. THATS IT. I WOULDNT WASTE THE $$$ ON A SMALL BASE CIRCLE UNLESS YOU ARE GOING CUSTOM SPECS....
JUST MY .02

[Fasteddie753]

I pulled a SB400 out of a '73 Caprice in '94. Ran it for awhile as a two-barrel stock for a year. Tore it down, had it punched .030 over, added Dart heads w/ 2.02 valves and screw-in studs. Cam is just an Edlebrock .440 lift I/E @.050 (need vaccum for brakes). Put an Edlebrock RPM spreadbore intake on, ran a Holley Q-JET Replacement w/ headers for awhile. Car raced! Added a 2500 stall w/ 350 trans and GN rear @3.42. This thing gets out of the hole fast and barks third! Went back to a polished big Q-JET out of a 500cid Caddy. Through gen. 2 exhaust manifolds back on w/ 2.5 pipes. Lost alittle in the mid and top end. Car still romps (without the exhaust leaks).
There are somethings to watch for. Clearance is one! I had to shim the radiator shroud about 1/4" do to the taller deck height of the 400. If you have a cooling cover on you distributor cap, you'll need to trim a cover off the windshield whipper actuator. It will hit the top of it.
My next move is to replace the oil pan and stock balancer. I may go to an over-drive trannie as well. It's a real sleeper.

They don't call it the "Mighty Mouse" for nothing.

FE

[dwagner1974]

i have a 400 +.30 .. complete roller motor with aluminum heads with 210 valves,658 lift cam and tons of other go fast goodies .. it runs cool as a cucumber and its cranking out around 750 HP @ 13.5 to 1 compression .. talk about torque .. its a great engine .. i have 2 others im building just like it .. you will love it !!!

[84 G camino]

FYI...the 400's extra cubic inches come from the bigger bore and longer stroke. the deck height is the same as a 262/283/305/etc.

[FrankJames]

Hey Turbo-how does that 400sbc run with the 700R and gearing? any 1/4 mile times- i'am thinking of running a similar setup on my 74 elky