Is there any difference between the 2-bolt main and 4-bolt main blocks? Other than the obvious if the mains.

I was told that the 4-bolt's web and the wall of the siamesed bore is thicker and stronger than the 2-bolt. Is this true? I am looking at picking one up but I want to know what I am getting before I buy.

Thanks.

 

That is backwards.

The later blocks, which were fitted with 2-bolt caps, are the ones with thicker main webbing.

But it's a very fine point; for most street uses, either would be perfectly OK.

 

IMO the two bolt is the way to go. People have had problems with the four.

 

the 2 bolt is actually stronger.

the 2 bolt block with aftermarket 4 bolt caps that go at a angle into the block is the strongest.


ive heard a rumor, never been confirmed as far as i know, that the earlier 400 blocks came with the steel crank, and the later ones with the iron.. not sure on that one though.

 

if i would have written my crank numbers down I could have told you.

I have a 511 block 4bolt mains I was "told " they are weaker but, I was also "told " they over heat

 

The 4-bolt blocks are definitely weaker; but it definitely doesn't matter about 95% or more of the time, depending on what you're doing with it.

About 99% odds the crank is a 510 casting like virtually all the rest of them.

 

they may be weaker, but there have been people running 10s consistantly with them for years... i dont like giving out a HP number saying "it'll hold out till XXXhp before it breaks." but it will hold almost any street engine..... obviously if you are doing somthing extreme you want to go a few extra steps, but for the most part, theres no reason to search for one block or another.

 

If you are worried about the strength of your block here what you can do.
Install splayed caps, which will cost about $500.00 to convert the 2 bolt to a 4bolt.
The next option will be to install ARP Studs then get the block align honed. The studs of a 2 bolt should hold over 500 hp with everything being blue-printed w/ all the correct clearances.

Here is a Picture of my SBC 400, casting is a 2 bolt 817 that I bought for $50.00.

 

***awaits the "it cant be a 400, it only has 2 freeze plug comments***



someones gonna say it.

 

I have a question about head selection on a 400. Do you have to use heads with steam holes?

Another question. When destroking a 400 with a 350 crank do you need to have machine work done?

 

Do you have to use heads with steam holes?
YES, If its a street engine you must drill steam holes. For DRAG/STRIP ONLY no because it would not run long enogh to overheat, However as a precaution I would Always drill the holes.


When destroking a 400 with a 350 crank do you need to have machine work done?
You CANNOT use a 350 crank in a 400, to destroke a 400 you would use a 400 crank with the 350 stroke (3.48). SBC 400 have Large Journal, while 350 have Medium Journals.

 

They will know better when the see the boss for the 3 freeze plug, I hope........

 

How can it be a 400, it only has two freeze plugs!



Sorry, I couldn't help myself. The temptation was too much....

 

I am just full of

 

mmmmmmm fisrt things first.......stroked means more......destroked means less........and yes 400sb comes with both 2 and 3 freeze plugs depends on years.....now destroking a 400 is a 400 block with a 350 crank....the bearing journals of the 400 crank is 2.650 the 350 crank journals are 2.450 .....there is a difference of .200 thousanth's of a inch.....to take up the difference you need a set of bearing spacers.....comp cams have them and jegs also has them
comp cam...#249-5620
jegs............#555-25000
those are the part number for the spacers.......other than that every thing else is a straight forward build

 

Only reason I asked about destroking was the fact it would probably make good high end HP. Maybe rev alittle higher than a standard 350 or 400 would. If I could find a 400sb near me I would build it...damn circle track racers around here have depleted the supply.

You can't hardly find a 400sb here to save your life.

 

This information is 100% incorrect. Many many people destroke thier 400 with a 350 crank and even sometimes a 327 crank (like me). You need to purchase the correct spacers for the crank to fit in the block along with the correct rod\piston combo and everything will work fine.

 

information is 100% incorrect explain correct for us then....

 

Like the old saying goes there is more than one way to skin a cat.

From what I know of them, its definitely better to build it with an aftermarket crank with 400 mains, but a 350 stroke. You can do it with the stock 350 crank, but you have to use spacer bearing to make up for the difference cause the 350 crank has a smaller main journal size. But when you look at what aftermarket cranks cost, then why not just build the 406?

 

re-read the entire post, including the quote. They were saying there is no way to use a 350 crank in a 400 block

I might have caused confusion because I saw him say that and then posted before i read further, that other people telling him the same thing already

 

destroking is stupid unless you have a Ci rule you need to follow.


you make your destroked engine go as high as you can......

then i'll make my 400 go just as high, and make more power.


the only way this distroking idea came about is some classes do have a displacement rule. and a big bore short stroke is better then a small bore long stroke....


but niether are as great as a big bore, big stroke.

people, we have the technology. we can make it stronger, faster and bigger then ever before!

 

That pic up there is not a 400 block... it only has 2 freeze plugs. JESUS stop posting mis information... every day i see this crap. over and over.

 

hehe, and now time for the word jumble.


todays word jumble is a special one for bigals87z28.

UPSHUTTUHEFCK

 

HEY!

 

bwahahahahahahaha! excelent pic. i like dogs.



cat tastes better though.. esp with a nice fish sauce......

 

bigal there are 400 sb with 2 freeze plugs , just as some of the old timers that been racing for years or go by a race type machine shop and ask them

 

Im kidding due to what several people said above.

 

I was just wondering why everyone wants a 400. I have a book on Chevy small blocks and all the info on 400 is that Chevy thought they should make an engine that had more cubes which equals more power in poeples eyes. But when building the 400 the engineers just ran into a lot of problems. The book said the the whole bottom end was very weak and thats why the first few years only came with four bolts to relieve stress on the crank. Also there was something about the number one rod having to be modified which reduce matterial and therefore durablity so it wouldn't damage the block. This is why the 400 only came in light duty trucks and large family cars. Not to say all of this is totally true because the book also said the 350 wasn't originally meant to be a performance engine until the engineers were told the engine ws going to be used in the high performance SS Camaro. So the 350 had to be built to with stand alot of stress. Thats why the 350s were the first chevy motors to get 4 bolt mains. So if the 400 was never designed for a performance vechicle or offered with a performance package why do you all won't it other than the more cubes more power. I'm also buying a truck tomorrow with a 400 and i don't plan on keeping it. I can sell it and buy a 350 and have money left over and not have to worry about breaking it.

 

uum, somtimes theres a LARGE diff between what somthings designed to do, and what it does.

the 350 was not ment for performance when it was orignally designed either.. like you said.



fact is though, you can make more power, more reliably fromt eh 400 then the 350.
if you're stupid enough to sell the 400 for a 350, more power to you.. i'll even trade you your worn out one, for a 100% reliable non performance fresh 350.

yes, there are weaknesses in the 400 engine... but in the last umm, say 30 years or so, i think we got most of them covered

i think that by now we really know what it can and cant do.

 

I think that you answered your own question: More cubes =more power! doh: Next don't believe everything that you read, they are trying to sell a magazine. If I was near you I would take that block off your hands for about $50.00 since it's a non performance engine and could use it for my non performance car.
Just think about this: A 350 and 400 with everything being equal, the 400 will produce more power. Most people if they did not want power they would have bought a slant 6 or low budget 4cyl.

 

btw, i find the term "weaker" to be misleading at times.



sure rod X may be weaker then rod Y.... but if they can both handle over 400hp, and im only making 300, it doesnt matter to me.

just a example, but get what im saying?




also, i have a couple camaro performance books that have stuff that is wrong now... back then it was the best way to do it, but today, it isnt.

the world changes.. printed word usually doesnt.

 

Hey I'm not stupid if I sale this 400 it isn't gonna go cheap, I know there worth. Also my 350 isn't a performance 350 just a truck motor. So i know what you guys are saying. I was just saying what i have heard and all this stuff has made me decide i would rather build a 350 rather than a 400. If I had money to blow on whatever I wanted then sure I would build a 400 but I can sell the thing buy a 350 for the truck the 400 is in and have money left to put in my Camaro. But I do believe most the things this book says.

Also more cubes isn't all that make power. A 350 Chevy will make a lot of power than a 350 Pontiac. And a 351 Ford won't always make more power than a 350 cause of one cube.

 

lmao, ****, you're asking for a rather large debate with that one.. lol..

theres more to a engines design then cubes... lets leave it at that..


now if the design is basicly the same... for a performance app, more cubes is better unless theres a rule agiesnt it.

thats why a 400 is better then a 350... basicly the same design, with a larger bore and stroke.






and since you already have a 400, why get a 350?

everything you would get for the 350 works on the 400, and the 400 will make more power for you with the same money...

not to mention, the cost of the cam is generaly the same for similar sizes.... so you can get a slightly bigger cam, at no extra cost, and it will run milder in the 400 then the 350 and still make more power...


im not seeing a downside?

 

I see the downside: 2+2=3
You idiot it's 4........:lala:

 

okay, for starters on arguing over the freeze plugs, I have 2 motors. one is a 4 bolt with 3 freeze plugs. the other is a 2 bolt with 2 freeze plugs. both exist. leave it alone, please.

second, the 400s are not an unreliable engine when built. unless you screw it up. you can build a 4 cylinder mercury lynx motor to handle 700 hp. so a 400 can be built to handle plenty. it is a mattter of what the individual does with it.

third, with all things equal, the larger displacement motor will produce fairly even hp but will decimate the smaller in torque. therefore, more cubes means more power.

lastly, before it begins, the overheating myths are exactly that, a myth. it is just like above, if you dont set it up to be cooled, it wont. that includes the overheating that came with people not drilling steam holes.

Now, as far as the original question and the posts actually responding to it, if I decide to build the 4 bolt, is there anyway to increase the strength? I know I can replace the caps and bolts but are there any other modifications that can be made to make it tougher?

I am looking to make around 400-430 hp and 430-460 lb-ft of torque. I am very confident the bottom end will hold, no problem. but, I want to have it strong enough that if I want to add a little more later, I do not have to rip apart the entire motor again. so I am wanting to give the bottom end a 600-700 hp capability. not that I will use it, but, better safe than sorry.

 

Have the deck 3/4 holes plug and tap with 3/16 holes wil;l strengthen the deck surface. I have done this to my block, just waiting to get the gasket to have the 3/16 holes drilled. Other than that, you know what its going to take to hold up. i Will take a picture later and post my deck 3/4 plug taped.

 

do you think a nodular crank will hold up or do I have to spend the money on a forged?

DTL, what heads are you running and what kind of numbers are you getting? I am curious of what combinations are working. I am also looking to make sure I keep the CR down under 10.5 and keep a resonable enough amount of vaccuum to operate the "luxuries" that keep it streetable.

 

Remember this most engine failures are not due to having a cast crank. What usually happens is the rod/rod bolt usually break causing damage to the crank. I know alot of people that run a cast crank over 500hp, but have the nice rods to compliment the crank for extra strength. So I would invest money into a good set of rods and a nice Scat 9000 or Scat 5140/4340. You can usually find these on ebay really cheap.
I have AFR 195 heads, Also if you want more power over that XE 274 run a solid cam from a good grinder. I would suggest that you talk to Harold of Lunati, he have some real nice lobes that are much fatter @.200 then most out there. Dont pay to much attention to the .050 numbers.

 

As far as the mains go, you can do three things to make it stronger. The first is to look down the bores from the top of the motor and you will see the main bolt threaded holes coming through the main webbing. Break out the die grinder and debur then polish this area. You can eliminate stress risers much like you do to a rod.

The second is to use quality main studs instead of main bolts. Main bolts put stress directly on the area of the main that has been known to crack. A stud equalizes the clamping force between the main webbing and the main cap itself, taking quite a bit of pressure off this area.

The last is going to cause some controversy but it works. Use Hard Blok block filler. Use the recommended street fill which concentrates on the main and bottom bore area. If you have a good clean sound cooling system, you will experience no cooling problems and will have gone a long way in making your block stronger.

While the suggestion of using deck plugs doesn't help the mains, it sure is a good one. Use deck studs or head studs for the same reason as the mains. There a plenty of 4-bolt 400's living long and happy lives with the details above.