400 Small Block Engine

[big_al_71]

What is your opinion on a chevy small block 400? I am looking for ups and downs on this particular model engine which I am not familiar with..I am familiar with 454,350,327..It seems like this engine is not very popular down here in florida. Any advice I could get from you fellows will be very appreciated. Reason I am asking I have a guy that wants to sell me a small block 400 with 462 hp at the flywheel. I met this guy at a performance shop just swaping ideas, he heard me talking with the shop owner about me wanting to go faster with my truck this time around. The guy from the shop is a good friend of mine and tells me that it is a GREAT motor. The motor only has about 100 miles it was installed in a camaro but the owner of the car changed his mind and decided to have a 540 built for it instead. The engine is on a stand I went to see it and it was started and it sounded awesome, oil was at 50psi, it was loud because of the open headers it did not idle perfect as he claimed that because it has been sitting for about two months there might be bad gas in the carb's bowl. I am not worried about that as I can tune it I was concerned about any knocking or funny noises in the bottom end.However he told me that he would pull the carb off holley 750 and rebuild it just to assure me that it is the readl deal on that motor. I was in the process of building a 383 stroker for my truck while it is in the body shop but now seen this motor completely ready to go I started leaning towards it..I just dont want a problem motor as this truck is going to be driven alot on the weekends....

Thanks again guys and gals!!!!!

[lpaine]

There was a hotrod article some time ago about the"350 Chevy should have built" -or words to that effect, basically a 400 block/327 crank, long (6.20?) rods, about 11:1 compression, made awesome power on 87 octane,-around 400 h.p., sounded real interesting. Sorry, no link. Someone else might have a link.

[68Stepbed]

Big AL, the lack of popularity in the 400's is it's rarity and sometimes expense of building one. Also, the Generals versions had some pitfalls. The 400 is basically the reheaded stepchild of the GenI SB family. It's internals and heads differ slightly from other SBC components. The crank and rotating assembly is externally balanced where the others are internal. There is some kind of difference in the water jackets but I'm not familiar with exactly what the difference is. I just know it's there.

Something else to watch for, unlike the good ol' 350 that is stronger with the 4 bolt mains, the 400 4 bolt main engines are actually weaker. The outside main hole actually taps into the structural webbing of the block making it weaker and prone to cracking under high stress (high revving) situations. The 2 bolt main blocks are actually stronger. Engine builders have found that using a 2 bolt block and adding 4 bolt splayed main caps increase strength and durability though. The splayed outer bolt doesn't tap into the webbing causing weak spots.

On the upper hand, built right, the 400 has definite advantages over 350 and 383 engines. The 4.125" bore makes for a much larger combustion area which means more power. As we all know, the 3.75" stroke crank adds a longer throw making better low end torque. Also, the bore and stroke combo allows for just a tad better rev capabilities than the the 383. I've heard of guys turning stock cast crank 400's past 7000 rpm without problems. I knew a guy locally that did this in his race car every weekend for about 5 seasons before the engine finally gave out. It was actually a broken valve that killed the engine.

I say go for it. It sounds like the guy that built it knew what he was doing. The only thing I would change would be the carb. The 750 would be fine if you plan to drag race it alot, but if this is gonna be a street bruiser, I would suggest a 600-650 carb. You will have better streetabilty and throttle response from the smaller cfm carb.

[Old Yeller 1970]

As I understand it, the main draw back to the 400 sb is the amount of meat between each cylinder is much less than on a 350. Basically chevy bored out the sb as far as they could go without totally compromising the integrity of the block for daily use. The problem comes in when you start upping the performance.

Because the cylinder wall thickness of a 350 is much more than a 400, a 350 block can handle blowers and nitrous quite easily but with the 400 not so much. I don't think that means you can't do it to a 400 but I wouldn't expect the same life out of it as a 350/383.

However, as long as you keep one naturaly aspirated and it's built right, I think they are very good engines and I wouldn't hesitate to run one.

[ChevLoRay]

GM called the bores "siamesed". The holes between the cylinders were called steam holes, I'm sure for a good reason.

But, they are rare in these times. I called last weekend about a 400 for sale in my area for $800. It's still in a truck...GMC he says, it still cranks and runs. It's a small block 400. Most of them have 2-bbl carbs, although the 400SB in my '76 Blazer had a Q-Jet. It towed my '25-ft travel trailer up and down hills without any problems. The popular overbore around here, and other places, yielded a 406. But to buy one for this price and then have to rebuild it, isn't in my plan.

[Rodms]

My engine shop told me that just the core on the 400's were going for 4 to 500 bucks now just because they are getting hard to find,the problem with alot is that they wear the cylinders out because of the long stroke they'll be egg shaped.

[big_al_71]

Guys I really appreciate all your great feedback!!!!! I dont plan on having a race truck or adding any power adders, definetly I will drive it hard when I have to but mostly it will be my weekend warrior.
I spoke to the guy earlier today and he told me that the engine has a new crank, high volume oil pump,roller timing chain, ...I am going to possibly buy it on monday and take a chance..I will post some picts...

[Ford Assassin]

Alot of the 400's bad rep comes as a scapegoat for owner error or oversight. Especially about so called cooling issues. I've run several 400's, including one stroked to a 421.

I'll agree that due to their thinner cylinder wall that they are not the most ideal engine to use for forced induction, at least with a production block. Now using a Dart 400 block, that is another matter all together....

[truckster]

The bores are siamesed, meaning that the water jacket doesn't run between the cylinders. The heads have steam holes drilled in them (so that steam doesn't build up and cause a hot spot). Given adequate cooling, they're excellent motors. Make sure you get the right balancer and flywheel for the 400 or you'll have some incredible vibration.

[sleric77]

Where I'm from in middle Georgia the sbc 400 is the one of the most popular engines around . With the right heads , cam , intake , carb you will be well pleased with the 400 . I,m putting one in my 85 silerado and I have a backup 400 in my storage building . Just the block alone will easily cost you 400 dollars around here .

[big_al_71]

Is it monday yet????

I am so ready to go pick this motor up and get it to my standards,,,,march pulleys, repaint, billet valve covers and air cleaner assy..


again thank you all!!!!!! you are the best!!!


One last thing I hope this hurricane does not come our way!!!

Hurricane lurking in the atlantic oh boy,, welcome to florida!!

[redhead69]

Your going to love it! Mine is way milder than yours and its a tire fryer for sure.. post up some specs if you can get em from your builder.. Id love to see the combo you'll be running

Red

[bigsnookmaster]

Big Al, I hope you bought that motor.Put it in your truck and you'll smile from ear to ear,if you want to go fast and be able to boil the tires any time you want.I've been running them for about 15 years and I haven't had any other small block since I got my first one.I've never had overheating problems,but I've always had a jamb up cooling system.You'll need a good posi and replace your u-joints with good ones.I currently am in the final build stages of my 68 short step with a 406.I run a 4-bolt splayed cap motor,mech. roller cam,Jesel shaft rockers,Victor jr alum heads,Hooker super comps with a 3"mandrel bent exhaust with an X pipe,and elec. water pump and fans.I'm estimating 540-550 hp.This motor seems extremely responsive,and I'm guessing the truck should run 6.90 to 7.20 in the eighth.Good luck,and let us know how you did.

[boogie67]

My sons 72 has the 400 out of my 56.Its been in his truck about 4 years now with no problems.That thing will get up and go and its stock.

[big_al_71]

Well gang due to this so called fay storm I was not able to go get the motor today being that everything was closed down including my bank. I am hoping that tomorrow things will go back to normal and I will be able to pick this motor up. I will post picts of it as soon it is in my possesion.Big snook I will be looking for you when is time to sey this bad boy in my truck..I really appreciate everyones input and heads up. I will get a detail run down of everything that is done to this engine with all the specs...Even sending my truck to the body shop might not take place till thursday or so..Florida weather !!!!

[corn]

I love the 400's.

[grayw0lf]

The 400 does seem to put out more heat than other small blocks. You want to consider upgrading for a 4 core radiator.

[arkansas]

I've been running a very mild 400 in a 49 chevy coupe with a 700 tranny and 3.73 posi for about 5 years. It's a great combo. I have to baby it all the way through 1st gear because of traction issues and it still runs under 15.5 seconds through the 1/4. Roasts the tires whenever you think about it, gets about 15mpg. I'm running a 650 holley with a "rv" cam. Otherwise its stock right down the bore. I got lucky and bought it complete with a brand new Edelbrock intake minus the carb and alternator for 350.00 from a cousin. Very torquey. If you can find one go for it. I am running an aluminum radiator to take care of the extra heat issues, but it never gets over 180.

[sweet572]

i love the 400 in mine, its been 4-5 years and no problems at all and it flies when i need it to

[special-K]

I had a stock 400 in my`72 K/20 Highlander with 4bbl dual exhaust and HEI.The difference in torque between a 350 was very noticeable.The truck was a amanual and it would chug like a tractor.My friend races 406s built from factory blocks and loves them.

[Bob B.]

I like 400's too, they can make Big-Block power in a light small block package. Lots of good information in this thread, but I would like to add something more: SB 400's got a reputation for using more oil than other small blocks, and even when new some would use 1 qt. per 800 miles. The reason for this is not as some think the siamesed cylinders. The culprit is the fact that the head bolt holes are very close to the cylinder walls. The head bolts are in the same place as any other small block, and with a 4" bore there is still plenty of meat between the bolt hole and the cylinder wall. Problem is that the SB 400 has a 4.125" bore, and when the head bolts are torqued down, it can actually cause the cylinder wall to bulge out very slightly near the bolt hole at the top of the cylinder. That bulge will cause a bit of a piston ring seating and wear issue, and often if you look at the cylinder walls of an SB 400 with a lot of miles you will see 5 shiny spots right near the head bolts. You can't really measure the wear, but the cross-hatch will be gone. Luckily, there is a good solution to this problem. When you bore and hone the block (and you shouldn't really bore an SB 400 over .030", maybe .040" if there is absolutely no core shift) be sure to use a torque plate. This will cause the slight bulge around each head bolt hole, and when you cut you will get a perfect cylinder with the head installed. It is also a good idea to install and torque the main bearing caps too, as the cap bolts can cause a bit of distortion in the block as well.

[big_al_71]

Well guys I finally picked up the "400" and a th350 tranny with a 3,000 stall converter..While the truck is at the body shop I am going to make this bad boy look good.
List of things going on it:
March Pulley v belt set up.
New aluminum water pump
new fuel pump
new oil pan
new carburator
new msd dist.
new taylor wires
new plugs
new headers
new holley 650 or 750 not sure yet
billet specialties or edelbrock classic valve covers and matching air cleaner
new paint on the block and heads

[bigsnookmaster]

I agree with Bob O 100%.I used torque plates on my 400.They should be used on all serious re-builds and especially 400's.It's really not that much extra when you look at the longevity standpoint. I also run a moroso crank scraper,pan baffle,and windage tray.This keeps the oil off the rotating assembly.Kinda like comparing running through a puddle vs running on dry land. You know which is faster.Good luck,keep us posted,and let us know the specs.on that motor when you can.

[Black_Duck]

Nice engine stand

[big_al_71]

Originally Posted by Black_Duck

Nice engine stand

I was waiting for that one!!!!
That is what the guy had it on,,, I laughed my ass off!!!