gkull

You have severl things going on with a 400 block that makes it weaker in the main saddle area. The additional .125 bore size takes away strength. The large 400 crank diameter takes away strength from the caps and saddles. Lars put on the ford idea main cap straps. You can buy bigger beefy main caps.


how a stud works is that they are not TQ down in the block like a bolt. just finger tight. Each time you TQ a bolt down you are causing micro fractures of the material being threaded into. So the nut on the stud is TQ down to what ever foot pounds and it just does a straight pull on the block.

Studs are not a different diameter. You just chase the threads to clean them up and install them. Some studs I locktight in place. ARP studs can be very strong like 220,000 psi steel.

As to the stud diameter holding something better............. No because it is the same diameter. Main caps are machined to fit in the block. Actually they are such a side to side tight fit that they are difficult to knock in or out. Aftermarket blocks are so superior in amount of metal. My Motown and Dart iron blocks are something like 35 heavier just as a bare block.

gkull

This is a picture of splayed caps on a total race motor that I worked on many years ago. Memory fails me, but it was a Rodeck or something aluminum 410 ci sprint car motor with 15.8 C/R running a kinsler 8 stack FI on methanol.

you see how the main caps are captured by the block for no side movement?

cardo0

Well I can remember reading several times that 500hp was the reasonable limit for a stock block though you will find them built to produce way more than that but who knows how long those last. If you look at any GMPP catalog in the table for sbc blocks you will find the rating of the stock Chevy production cast iron blocks is 500hp while the BowTie blocks have a much, much higher HP rating.

But ya know 500 hp is whole lotta hp on the street. A true 500hp motor is quite an animal on street tires and very hard on the rest of the drivetrain. The cost factor is as true today as it was 30 years ago for the sbc. Building a 600hp sbc will cost at least 3 times as much as building a 500hp sbc. All I can say is once I get to a 500hp sbc l will let everyone know if that is enough or not.

Pop Chevy

A sprint car motor with a wet sump ????
The 509 block (casting no) had a higher nickle content. Years ago the sprint car guys used em , they were limited to 410 cu in .

Jebbysan

I used I believe the 510 block....it is a four bolt....and it is fine for my 6000rpm cap and 500 horses....
Anything beyond this is not economically viable....by the time you pay for the machining...and drilling the block for oiling mods you are into a Dart block.....

And yes....it will pop motor mounts as Lars says.....my first 1-2 shift did this very thing

Jebby

cardo0

Seller not returning my calls. I will try a few more days but I think he got tired of waiting.

Why do some of the best deals in life happen when I'm not ready for them? Always looking for a good deal and that's what gets me in trouble. My garage is to full already. Yes your right I just need a bigger garage.

But I think I still have good leads for a 400 bare block once I am ready but for closer to $500 than $300.

Anyways thanks for all the advice folks.

Kacyc3

My comment wasnt about making more hp but about the reliability of the block at desired power levels.

MotorHead

I would spend a little more than $500 and buy an aftermarket block like an SHP. The used 400ci block is going to need machine work and that can quickly add up to near or more than a brand new SHP block.

In a high performance engine the block is one of the less expensive parts of the entire build. For a good HP engine you want quality parts and when you look at the bill the block is peanuts compared to the rest of the parts.

Been down this road before. You spend $500 for the the engine and it's a crap shoot if you can use anything off it. The block might not even be serviceable. Go with an new aftermarket block and have some piece of mind

cardo0

Well I wasn't aware the aftermarket blocks came machined and ready for parts. I thought they still need honing if not boring along with align hone/boring for the crank. Zero decked? And they still need cleaning.

Something of an advantage of a "seasoned" used block is it should no longer change dimensionally with temperature cycles resulting in better ring seal - for the long term.

It really comes down to where or which one gets the better/best machine work for the dollar. If someone has a quality machine shop locally with reasonable pricing it would be the deal maker. If not it would be a deal breaker.

For the size cam I use and the RPM range I don't need to spend a dollar more than needed here.

StraubTech

Ditto....With the SHP Block, improved oiling, and a 350 main size I would not waste my time on junkyard 400 that could have all kinds of issues.

Gale Banks 80'

One odd problem I had using an aftermarket Block was the Pistons. Since the Block was new, and had the Original 4.125" Bore, I needed to have custom Pistons made by JE as they didn't stock stock sizes. It would of been cheaper to bore it 30 over but I just couldn't do that to a new block.

StraubTech

Most offer std bore pistons now with these new blocks available.

Richard Daugird

I got a 400 long block yesterday for $200. Haven't inspected it yet.

cardo0

Awesome Richard! There's a lot of those blocks sitting in someone's garage just taking up space. But I have come across neglected blocks with to much corrosion to bother with. Actually I've found that assembled blocks keep the rod and main journals protected and most of the cylinders are sealed - though 1 or 2 will have a valve open.

Good luck with yours.

cardo0

Just to share with you all for the holiday weekend I recently found a 400 block with standard bore. Got it off eBay but local for $1 per cubic inches. I was kinda upset when I had some say they had good 400 block to sell me but quit answering their phone the day I was ready to pick it up - haven't figured that one out. I was on vacation that week and wanted to take care of a 400 block purchase but it seemed like all the regular sources for 400 blocks had dried up. When I saw this block I jumped on it and picked it up ASAP.
Take a look as I post the pic on cardomain. Somehow posted them 3 or 4 times - oh well. Tell me what you think. If you can zoom in you can see the massive ridge at the top of the cylinders. Also a couple of cylinders have a vertical scratch. Hope to clean up with boring.

http://www.cardomain.com/ride/445470/1974-chevrolet-corvette/

Still looking for more 400 blocks as I have some more ideas for them. But the ones I have seen on CL had damage/repairs to the block or already rebuilt cores. But I'm good for now. If I really wanted a max effort 400 block I would use aftermarket. The BluePrint blocks look nice for$1600 but still need some machine work for what I want to do - not much but it does add to cost.

Cardo0

69Vett

your looking at a used block, and crank. anything else (parts value) is a maybe.
the SB 400 chevy is very easily overheated, couple that with poor C3 cooling capability.
and you may be asking for trouble down the road.

george2066

I am with gkull, dart shp

diehrd

I second this. Doing a motor is a major deal. No sense IMOP to NOT get a fresh new bottom end , heads and cam .

AND its also pointless to AVOID big CI small blocks. U have no idea what you are missing. Easy of install and BB Torque are a Corvette owners dream come true

cv67

Wasted so many yrs trying to make stock stroke stuff satisfy
Back then there was a myth that strokers were just low rpm motors sheesh if I only knew-

Kept a perfect 509 block for yrs, couldnt bring myself to build it as I like to twist em. By the time the machinist was honest with his estimate..for another 500 i could have bought a Dart Little M and had apeace of mind it would have been rock solid. Regrettably let the block go, last thing I want when that tach is swinging is to worry. Seen more than one guy spend bucks on a GM 400 and hear a "tink" when torquing the head bolts down. (crack)

make sure you double ck the machining on these new blocks. yeah its more money but sometimes you find stuff that is a little off.

I found on the Little M the cooling jackets were FULL of metal shavings.

very happy going from a 350 to 383..still kinda wish id gone right to a 421 or stuck that blower on this one rather than a big SR and heads.

v2racing

This is another myth perpetuated about the 400's. Not only have I never had troubles with a 400 overheating, I've known many people with 400 powered vehicles going back to the 70's, and 80's drive them for many trouble free miles.

Yes, if you do overheat them badly, they can crack blocks. Moral is, keep the cooling system in good shape.

Stock 400 blocks are hit and miss. As I've said before in other threads, I've known guys who pushed them very hard with no problems for years. One friend was making 560 HP and 530 TQ with a 200 shot of nitrous on top. He ran this thing for 10 years or more and beat on it every time it was driven. He had a stock cast crank in it too. The last time we tore it down the crank was cracked. We built him a Dart raised deck and big block cam all aluminum 427 sbc.

As others have said, sometimes they don't make it past assembly and crack when torquing heads.

An awful lot of them went on dirt tracks before the aftermarket blocks were available. A friend of mine was running a 700 HP plus sprint car in a stock 400 block. This was a winning car and he didn't have engine failure problems.

Stock blocks are a crap shoot, but good ones can live pretty well at fairly high horsepower levels. Of course the aftermarket blocks are far superior.

Mike