400 sbc

[Guest wacyszcar]

theres a guy down the road who has a 400 sbc in his 79 chevy blazer, its the original engine and has never been rebuilt. it has run good for all the time. he is going to take it out and put in a 350 chevy. he said to make him any offer. would i be better with a 350 or a 400. i know the 350 is cheaper to rebuild but 400 s are bigger. what would have more power. i heard from somebody the 400 is a crappy engine. anyone?

[DavyZ]

theres a guy down the road who has a 400 sbc in his 79 chevy blazer, its the original engine and has never been rebuilt. it has run good for all the time. he is going to take it out and put in a 350 chevy. he said to make him any offer. would i be better with a 350 or a 400. i know the 350 is cheaper to rebuild but 400 s are bigger. what would have more power. i heard from somebody the 400 is a crappy engine. anyone?

 

I can't tell from your post if the engine is in need of rebuilding or not. I would ask myself these questions:

 

1) Why is he getting rid of a good motor for a smaller one?

2) If the 400 needs a rebuild, why doesn't he just rebuild it?---it makes more power/torque than the 350 all things being equal.

3) Is the 400 rebuildable? Is there any reason why it's not?

 

All things being equal, always go for more cubic inches. I'd love to have a 400 sbc in place of my 350. For N/A motors, nothing beats cubic inches.

 

Davy

[Guest CRrider1988]

I would stay with the 350. My dad use to build tons of 350's back in the 70's and 80's and still does build alot, he sends the 400's to the shreder. he was saying that it is just not as well of designed motor, you cant get as many parts, the parts you can get cost more, and they dont build as much power. The only plus is maybe a tad bit more torque. There has to be a reason that the 350 is so popular and the 400 is so unpopular.

[DavyZ]

I would stay with the 350. My dad use to build tons of 350's back in the 70's and 80's and still does build alot, he sends the 400's to the shreder. he was saying that it is just not as well of designed motor, you cant get as many parts, the parts you can get cost more, and they dont build as much power. The only plus is maybe a tad bit more torque. There has to be a reason that the 350 is so popular and the 400 is so unpopular.

 

Not everything he said is true. You can't build as much power?!? That's flat incorrect.

 

Here is a build up of a 400 SBC if you are interested, wacyszcar:

 

http://chevyhiperformance.com/techarticles/6113/

http://chevyhiperformance.com/techarticles/148_0306_406/

http://ncarboni.home.att.net/Engine.html

 

Davy

[Guest zfan]

A 400 sbc will make way more power than a 350 using the same parts. There is no replacement for displacement.

 

Mike

[Psykovertible]

well to put my 2 cents in... if you build a 327, 350 and 400 with all the same specs meaning compression and parts type/grade, they should all make very similar HP but more cubes means more torque. I love 400's cause I like big cubes. They may be overkill in a Z due to traction issues, but isnt that why you wanna V8Zcar to begin with? GO for the gusto but if that particular motor is not buildable then it is a waste of money. If you want bang fot the buck buy a GM Crate motor to get a a good 4 bolt main SBC with a warranty.

[Mike C]

Everybody has good points. Problems with the 400 is core shift in some cause cooling problems, especially if overbored. The short rods are crappy, and the factory cylinder heads are pathetic. A 400 needs a larger intake port volume head than a 350, so if you already have a set of heads, take that in to consideration. Also as noted, pistons are more expensive.

 

But your dad is nuts. He's pissed off a ton of money if he's scrapping 400 blocks. A good one is worth 50% to 100% more than a 350. And the old adage aalways holds: There's no replacement for displacement.

[skipzoomie]

Well, everyone has an opinion. Most are not based on any factual information. There are no "CRAPPY" small block Chevy engines. There have been some produced that don't fall into the HiPerf catagory. But they are very servicable, reliable, and long lived. The small block started life as a lowly 265 cubic inch service motor and that engine design lives on in every small block ever produced. The Chevy small block is the most produced engine in automotive history. In my opinion that does'nt spell "CRAPPY".

[Here comes trouble]

Check the post on the 400 rebuild sites...about any problem with a 400 block can be overcome.... $200.00 or less would be a good price on a rebuilable block.... call some engine rebuilders and ask what they would be willing to pay for a rebuildable long block. these blocks are in short supply and in demand

[pparaska]

The problem with building a 400 is finding a good used block. They don't take well to anything more than .030" bore usually, so after the first rebuild, it takes a good sonic test to find out if it's worth a bore.

 

I had a .030" over 400 in my Z, but the builder used a sleeve in one cylinder.

 

The shop that bored the replacement Dart Little M block said I probably just ran the sleeved engine lean and caused the sleeve to separate. I bet he's right. Just before it went bad I was giving a joy ride and the tuning was not good.

 

Anyway, if you're doing a 400 build, do what my machine shop tells people to do - "get a real block", i.e., a Dart Little M. $1800 is not cheap, but it is good for more power than you'll probably ever build it to, and more than you can use in a Z.

 

Go with 6" rods, and the pistons will be short and light (I used Probe SRS). That enables you to use a light crank that can be internally balanced. The rod/stroke ratio is about the same as a 350 with 5.7 rods, so the rod angularity is about the same, which should give the same level of wear in the bores/pistons.

[Alf]

a 400sbc has a 4.125 inch bore and a 350 has a 4.00 inch bore. since the sbc only has 4.4 inch bore centers, 4.125 is pushing it. chevy's solution to this was to siamese the bores. this means that the bores are all conected and there is no water passage where the adjacent bores are closest. that is the only drawback of the 400. unless you are building an extremely high compression/high reving engine you should have no problems. generaly an engine with more cubic inches will make 1hp and 1 ft/lb more for each inch(if the engine is in the 1hp per cubic inch range) for exampleif you build a 350 and say you make a conservative 1hp and 1ft/lb per cubic inch thats 350hp and 350ft/lbs. now if you build that same engine instead with 400 ci the motor will make 400hp and 400ft/lbs. larger engines are also more streetable with biger cams and carbs so you can expect more power and more drivability from the 400. what could be better than big block ci/power in a small block package. or you could look at it this way: why are you putting a v8 into your z? cause it creates a good power to weight ratio right. thats just what the 400 sb does. big inches, less weight. if there engine you are looking at is structurally sound i would definentally go the 400sb rought. good luck.

[Guest jbarker]

I have ran and still am running a 60 over 400 and had no problems. I conducted a experiment several years ago, I was running a 60 over 350 in a 73 Vega and it ran 7.00 in the 1/8th. I took the heads ,cam,intake ,carb off the 350 and put them on a 60 over 400. The car ran 6.73 in the 1/8th. There is no substitution for cubic inches. This is why I run 400 sbc,but my brother loves 350's. Here in South Carolina a 400 naked block will go for $200.00 to $250.00. J Barker from jnjdragracing

[pparaska]

I have ran and still am running a 60 over 400 and had no problems.....There is no substitution for cubic inches.

 

Glad to hear you're running a .060" over 400 with no problems. Mine would have been fine if it didn't have a sleeve AND I hadn't run it lean at WOT!

 

BTW, with the 327 and 400 blocks on engine stands next to each other the other night, I was explaining "There is no substitute for cubic inches" to my 9 year old daughter (who was helping me measure the bores and pistons for the 327.)

 

It seemed really obvious to her that an explosion in a larger diameter combustion chamber, connected to a larger stroke would make more power. I can see I'll be building a hot rod with her some day! Now to get my 12 year old son off X-box Live long enough to teach him some gear head stuff!

[pparaska]

I would stay with the 350. My dad use to build tons of 350's back in the 70's and 80's and still does build alot, he sends the 400's to the shreder. he was saying that it is just not as well of designed motor, you cant get as many parts, the parts you can get cost more, and they dont build as much power. The only plus is maybe a tad bit more torque. There has to be a reason that the 350 is so popular and the 400 is so unpopular.

 

 

I'm sorry, but I'm going to raise the BS flag here. This is an old wives tales. HybridZ is about NOT stating the same old mis-information over and over.

 

The parts don't really cost that much more, if any. And they are readily available. Pick up a few magazines or look at the offerings from the crank and piston manufacturers.

 

It's More than a tad bit more torque, it's more torque and hp across the 1000-6500 rpm band, figure 1.2hp/cubic inch more.

 

Sorry to dis your dad's opinion, but there are many 400s running around on dirt tracks proving this just plain wrong.

[Psykovertible]

me, father,father in law and brother and law are avid 400SBC folks. parts are readilly avialable. not quite as market-flooded as the 350 parts though.

 

BTW... that BS flag is so cool that its the only reason i pitched in. I just wanted to try it out but cant figure it out. where do you find that stuff

 

 

(here you go, Mike kZ )

[ZuL8r]

If you are going with a manual transmission and are using the stock crankremember to check the crank to see if it is drilled for a pilot bearing. Alot of these engines were in automatic cars and were not drilled from the factory for a pilot bearing. My shop teacher built a 400 to go in his drag car and when he went to bolt the transmission to the engine he found out the crank was not drilled.

[dr_hunt]

Uh, if that were true, it is the one exception. Cranks take a pilot bearing for manual trans, so there is no drilling for that, just the installation of a pilot bearing, besides you don't drill something out to make it smaller. If my memory serves me correct used to be two OD bronze pilot bushings at one time.

 

400's in general are ok, I've run alot, built alot, building 2 circle track 400's now, pete is right, core shift, poor casting whatever you want to call it is the downfall, but it isn't that common. Ring seal is the primary problem with a block that has thin cylinder walls. Short filling a 400 makes a dramatic improvement IMO. If the 400 is junk, then just send them to me, I'll pay the freight.

 

Sleeves in the cylinders cause that one cylinder to run hotter because you now have a barrier inbetween the sleeve and the block. Run heat transfer calculations and you'll see what I mean, but it is common sense as well. In the old days it wasn't uncommon to sleeve all 8 cylinders on a 400sbc for a couple of reasons.