SmokinZ28

I got a block that is suppost to be a 2 blot main 400. Has factory steam vents and everything. Casting number is 3970010. Problem is when I run the numbers I get this

3970010
302
69
4
Z-28 Camaro

3970010
327
69
2
Trucks and industrial

3970010
350
69-80
2 or 4

I measured the bore on it (don't have metrics so this is a hope it's close enough) and it is 4 and almost 1/8th which is closer to the 4.125" bore of a 400. The walls look like they've never been touched and supposdly it's a virgin block. It has steam vents. I'm thinking its a 400 plus with that big a bore a 350 would be into the water jackets right? What do ya'll think? If it's an actual 400 then I'm going to have the mains splayed and build one badass motor

MrDude_1

how meny freeze plug holes are on the side of the block?

SmokinZ28

2 on each side

Cronic3rd

that would make it a 400

other small blocks have 3 plugs

AJ_92RS

That's not true. The 400 block has 3 freeze plugs, but not ALL 400s got 3 either. Some only got 2.

I have that same block. It's a 350 block.

kfoley

Well if it is a 400, which hopefully it is and you didn't get ripped, you don't really need to splay the mains unless you're putting out a lot of power. Just use good ARP main bolts or studs and you shouldn't have a problem. I'm building a 500hp 406 4 bolt main with ARP main bolts and I shouldn't have a problem.

Zepher

iTrader: (1)

Does it have a casting saying 6.0L or something like that on the top rear of the drivers side?
Not sure what a 400 is liters-wise, but my LT1 says 5.7L LG and my 305 said 5.0L LG

kfoley

A 400 is a 6.6L, but I'm not sure if that's on the block like on the 350's. I'll have to look at my block in the morning to see.

MrDude_1

only later model GM blocks got the liters cast into them. older blocks like 400s, dont.

400 blocks have 3 freeze plug holes in the side. this is because of how they cast them in the molds.

if you only have 2, then its probly not a 400. ive never heard of a 2 freeze plug 400, and heck several years ago, in a spotters guide, hot rod published the freeze plug thing as a way to tell a 400...... but i donno for sure if what AJ_92RS is true or not... so id just say that, its probly not a 400....

RB83L69

010 is a 4" block. Not a 400. It probably came from a 350, as it was a very common casting all through the 70s.

If in fact it has steam holes, someone else put them there; the factory didn't.

400 blocks don't have the "liters" marking cast into them.

Only the early 400s, 72-back, have 3 freeze plugs down the side. Those will be casting number 509 or 511. Most of those were equipped with 4-bolt main caps. No other small block casting has 3 freeze plugs. Later 400s, also casting # 509, only have 2 freeze plugs, and are therefore like every other small block.

Here's a set of heads with steam holes added. Note that they are close together, in between the head bolt hole and the one coolant hole (what you're probably misidentifying in the block as steam holes).

RB83L69

Here's a 400 block casting number. This one is a 73 model 509 casting.

RB83L69

Oh, I almost forgot..... here's a side view of that 509 casting.

Lots and lots of misinformation in this post. Seems to be becoming more common on these boards all of a sudden. Everything from mangled scientific fact, to historical details, to stuff like this, has been mutilated or confused lately. Let's all make a point of checking our facts before we send some poor trusting soul that came here for the truth, instead of the same monkey-spank you can hear on a Friday night in any McDonlads parking lot from high-school kids, on a left turn down a dirt road into the weeds.

gmgod

Does ANYONE know where to find 400's these days?

SmokinZ28

Thanks, the steam holes in this block are exactly where the one's in your heads are. I'll have to take a picture tonight and post it. How far can a 350 be bored before you actually hit a water jacket cause if this is a 350 then it's been punched further than .100 by my measuring tape which, by all means isn't going to be "on" but it's close enough to know if it is a 350 then it is bored out a lot further than it should be

RB83L69

A 350 block will usually go about .060" reliably. People sometimes go farther, but it's risky; and pistons are far and few between.

A tape measure is not accurate enough.

You have a 4" block in whatever overbore, believe it. The factory didn't accidentally slip the siamesed cylinder assembly necessary for a 400 block, into a 4" block, and forget to change the casting number. Steam holes are easy to drill; I do it all the time, usually in heads though. But it;s no different to drill them in a block. I can't imagine why anyone would do that though, that makes n sense, since the cyls aren't siamesed, there's no real possibility of steam formation to vent.

You find 400s in junkyards. You're not going to walk in and see one laying around; the people who run junkyards pull them if they are not blown up and you have to ask for them. Last time I needed one, maybe 4 years ago, I called up a friend who has a junkyard nowadays; he had 3 of them on hand, $250 my choice for a short block (like anybody cares about the heads anyway).

AJ_92RS

I'm sorry RB. I should have said it was a 4" bore block, not a 350 block.

Please forgive me!!! I'll never do it again!!! OH!!! THE PAIN!!! THE PAIN!!!

RB83L69

AH-hahahahahaha!!!!

Just don't let it happen again.

Otherwise, you could end up like me; I cause myself pain frequently, because it feels so good when I quit.

gmgod

The junkyards around here have been picked clean for some time now.

wesilva

iTrader: (35)

It is getting close to impossible to find a cheap one but if you look on http://www.racersauction.com you might find one that fits your budget. Use the word "400 block" for your search.

MrDude_1

i got my old one and my uncle got 3 of them from the older 70s "big" blazers...

Air_Adam

Look in the '70s tanks... namely Impala. I've heard a few trucks use them too.

Air_Adam

BTW, any block with the last 3 numbers being 010 is a 4" bore block.

The best way to tell if its a 400 is to measure the bore. It would be 4.125" if stock, 4.155" if its been eoverbored .030"

camarokev400

there is a pic of the steam holes in the block for you:

AJ_92RS

Is there an echo in here?






























Is there an echo in here?

:sillylol:

DartByU

All you have to do is check the main bearing bore size, 400's have a 2.65 main bore and 350's have a 2.45 bore size.

Rick289

Well, that's what I thought as well, right now I have 3 400 blocks and we are building some hot-rod test engines to see what we can get out of them as far as power and reliability? But I noticed the other Day that one of them has 3 Freezes plugs??? They are all 2-Boult mains and are all 4.125 bore to start with some had miles on them and we sonic tested them and are going to run a 6" rod so 2 of them are bored .030 over and 1 is board ,040 over other than the one that is being set up as a 377 Cid with a new 3,500 stroke crank from Scat 6" Rods and about 9 to 1 compression as it going in my 92 Chevy pickup! But it has 3 Freese plugs on the sides??? It's 2 bolt main, I'll have to get the cast numbers, but I believe they are all about the same? I like the idea as I have had a few chevy guys beat me or come close and then swore it's only a 355 Cid!!! LOL!!! as I look under the car and there is 3 freeze plugs!!! LOL! yeah! Right! now I know their secret! (o; Just looking for input if anyone know about this and/or why? Thanks, Rick289.

sofakingdom

iTrader: (1)

The three casting sand drain holes are a feature of the CASTING. The # of main cap bolts is an artifact of subsequent MACHINING.

2 very different origins for the "features".

Given GM's meticulous "quality control" in the 70s (read: NEVER let the quality get so high that an auditor might suspect it's out of control) there's NO TELLING what might have happened if they had some leftover early (3-hole) castings laying around but the current year's production called for only 2-bolt mains.

Casting #s for 400 blocks are 511 (early), and 509 or 817 (late). 511 had the 3 sand relief holes. (mostly at least) No idea "why" they did that; maybe they were afraid that the sand wouldn't be able to drain out of the side of the cyl area over toward the lifters, I just don't know. That only lasted about 2 - 3 years though, so whatever the motivation for it, it must not have made enough of an improvement to The Bottom Line (which is ALL they cared about) to justify the extra cost. 509, which is by far the most common 400 casting, came out for the 73 model year, and only had 2. Pretty sure 817 also had only 2 but don't hold me to that. That's probably the casting that the fewest of were made. 511 usually got the 4-bolt caps installed; but that was a kinda backwards step, because the metal all around where the bolt holes are, aka block webbing, was thinner and weaker even than 350 castings such as 010 or later 400s such as 509. Which is why none of us that were serious about these things back in the day, would build a 511 block for anything where block ruggedness mattered. Also, already having the factory's inferior and mostly useless (for our purposes anyway) parallel 4-bolt pattern drilled in a block, makes it much more difficult, even impossible in some cases, to install EFFECTIVE aftermarket splayed-bolt caps.

I did that for somebody once. He regretted it. Turns out, all else being equal, CID really does win races. Nobody has rewritten the laws of physics lately that I know of, in any way that would change that. More volume = more air/fuel = more power. Too simple. Don't outsmart yourself.

Rick289

Well, I picked up 3 400 Blocks to build Moters to try different combos for racing, one of them is going in my work truck a 92 C-10 and it will be a 377 destocked 400 as it will make more toque then the 350 that's in the truck now and, a lot more top end HP! I was doing a pre-assembly the other day when I noticed it has 3 freeze plugs on each side! the other 2 blocks are 2 freeze plugs on each side! The blocks are the same otherwise, NO 4 bolt mains and the same cast numbers! So, what is that? They are all 4,125 bores plus whatever I had to over bore them too to clean up the bores? 2 are .030 over and 1 is .040 over. I got a new Scat Crank for a 400 Main with a 3.500 Stroke! NOT a 3.480 Stroke the old way of using spacers for the mains and running a 350 crank to make a 377cid the hard way! I like it! As it explains why some of my friend's cars run really good and they swear it's only a 350!!! you look under the car and see 3 Freeze plugs per side and think well? It must be a 350. Right? Sure, explains a lot!! I love it! My truck will still have a 350 in it when I am done!!! LOL!!!! Thanks...

sofakingdom

iTrader: (1)

And that number is, ... ???

And that matters, because, ... ??? When you COULD HAVE HAD 23 MORE if you'd just built it as it was?

So you're NOT putting one of those 400 blocks in it?

No. Unless you're some thumbsucking n00b. 3 sand drain plugs (they are NOT "freeze" plugs no matter how many times you hear that on street corners) is an early 400 block. Anybody that thinks that means "350" doesn't know what they're looking at and therefore their opinion doesn't matter anyway.

Butt hay, you do you, and enjoy it to the fullest. It's your money after all. Butt since this is a forum EXCLUSIVELY for 82-92 Camaro & Firebird, we're not interested in a pickup truck regardless, and further discussion of it, especially when equipped with all the bishop-buffing, isn't welcome here.

AlkyIROC

The only reason to convert a 400 block into a 377 is if you're racing in a class that limits displacement. The wider bore of the 377 will make slightly more HP than a similarly built 383 although the 383 has more displacement than the 377 so it's really a toss up.

Compared to a 350 010 block, even the poor 010 castings are better than a 400 block,

If you're really serious about making power, just buy an aftermarket block. Nobody likes hearing the swap option but a simple 5.3L LS engine can make a lot more power with simple changes like a cam swap. A 6.0L LS is even a better swap.

84 1LE

iTrader: (9)

This post is from 2003, but nevermind that! What's with the letters in the circle appearing under the user name?

sofakingdom

iTrader: (1)

Looks like people who haven't posted an avatar pic have those.

I probably wouldn't have answered this necro post if not for all the n00b's pud-packing.

84 1LE

iTrader: (9)

Hmm, curtesy avatar.
Ive done that a couple times myself, i often wonder if they're bots bringing up necro threads.

WildCard600

I think it's probably mostly the horrible infinite scroll "feature" (I doubt most have turned it off) and people simply not paying attention to how old the thread is. I've nearly necro'ed 20 year old threads myself before realizing it's a couple decades old.

84 1LE

iTrader: (9)

The post date is the first thing i look at before i reply, but i have erred occasionally.

sofakingdom

iTrader: (1)

The post date order thing surely happens.

Not in this case.

This guy wanted to show us how stiffly he could choke his chicken. Something altogether different.

ironwill

Looks like an actual person bumped this ancient thread; AI-generated 'bot' posts are usually fairly short, consisting of very generalized, generic text. I've only seen one or two such posts on this site so far, but I expect many more to be coming here soon.