400 sbc

[86shorty]

Hey guys. I have the chance to buy a 400 smallblock just the block crank and rods for 300 $. Plan on just building it as money comes and dropping it in one day in my 86. Any thoughts about the 400?
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[LynnJr]

If its already been bored over pass on it.You don't want to take the 400's past 0.30 over.

[86shorty]

Nope its a stocker. From a 1970 impala. Its a 511 code 4 bolt main engine. Even specified that it is stock bore..but I know people can just talk
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[dieseldawg142]

had a 400 in my '76 K5. there's not a lot of metal between the bores, for a street driver, i would just do a bore clean-up.
you'd have to put a lot of good parts in a 400 to get 400 or more horse, but they make torque in spades. i did a mild build on mine, Isky cam, holley intake & carb, headers & a good flowing exhaust, & some mild head work.
dont know what the power was, but i never had to take a run at the hills (k5, 400, t350, 203, 10 & 12 bolts, 35's)

[86shorty]

I drive my trucks for torque lol I'm not a big horsepower guy. I'm not pulling anything but I've always loved high torque engines. I know there's always the arguement of 2 and 4 bolt mains especially in the 400. The 2 bolts having more material in the mains than the 4. I know a 4 bolt would do fine for a hopped up cruiser as I'm not racing or dragging I'm the truck..I guess the extra piece of mind knowing the truck won't throw a main eases my mind lol this engine is the 511 4 bolt main. I've considered possibly the 509 2 bolt main engine as a builder as these supposedly had a higher nickel content and the thick mains. Any thoughts? Or would there be any way to strengthen up the mains in this one?
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[dieseldawg142]

unless your spinning it past 55-6000 rpm, i wouldn't worry wether its a 2 or 4 bolt main.
mine was a 2 bolt & it had loads of meat around the bolts. haven't had a 4b main 400, but i've heard the outer bolts are prone to cracking around the oil pan rail.
if you think your gonna be spinning it high, i would throw some arp studs in there & call it done

[86shorty]

I thought so. I guess its either a 509 casting or shell out for a dart shp block. I'd like the 2 bolt just "in case" my foot slips eventually down the road this truck will transform from a driver to a mean machine. There are plenty of 4 bolts to be found around here..bit I think I'm gonna wait out amd see where and if I can find a 509 casting.
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[INSIDIOUS '86]

I regularly spin my 4 bolt main .30 over 400 past 6000 almost twice a week. No kidding I'm not nice to this thing. About 400-420hp with my big carb

Don't sweat the 2 vs four bolt main. That comes into play over 450hp and higher than 6500 rpm.

A well balanced rotating assembly will make a bigger difference more than anything.
Virgin bore is nice. 400's are hard to get so when you bore it do it right and get it bored square and torque plate honed. Run 3/16ths 3/16ths ring set for less wear and better and a little better power. All Ls engines run this just fine. And synthetic oil I kid you not will extend the life and wear of the motor easily.
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[86shorty]

That's good to hear! Ive heard mix reviews on the differences between the two. I'm really just looking for amean driver. Something I can take to the cruise ins and oogle at haha I won't focus on the 2-4 main thi g as much anymore. Theres a local selling a 4 bolt 511 code for 200 $. With crank and 300 with Mahle rods. Hopefu lly he still has it
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[INSIDIOUS '86]

Yah biggest thing is 400s have small rods. Squeeze some 6" rods in there keeps the piston sidewall from getting a lot of side load and good rods and bolts mean you can spin it good still up to 6500. Anything past that and your motor is still making power then you have the wrong cam for the street.

A 406 with the above and a 280 magnum cam and vortex heads or better will be a pretty good street monster upwards of 400hp easy. After 450 hp things get dicey some blocks have no problem and some do at that point. My local engine shop guy has seen a lot of 400s he does spring and circle track himself. This is the same stuff he tells me and there's a reason he's still in that small dingy shop for 45+ years.
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[86shorty]

Oh boy! I just got a call back from a guy with a 509 block that hasn't been bored! Crank and block for 300 $!
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[KQQL IT]

A 2 bolt 400 is generally preferred.

My 406 goes 6k all the time.
500ish HP

I've also had short rod and long rod versions
Current combo is a 5.7 rod only because they're more affordable and plentiful
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[K10Scottsdale78]

I have a 400 in my truck. Its a dog, but man does it make a lot of low end torque! Rolling in 1st gear the tires will spin if I give it half throttle

[86shorty]

Exactly! I got a guy in the next town over that has what I'm looking for. I've had many guys tell me its more worth it if I do a 383 or 377 cuz the block will be stronger. I'm aware the 400 is not known to be one of GMs strongest blocks..but man are they awesome!
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[INSIDIOUS '86]

Originally Posted by 86shorty

Exactly! I got a guy in the next town over that has what I'm looking for. I've had many guys tell me its more worth it if I do a 383 or 377 cuz the block will be stronger. I'm aware the 400 is not known to be one of GMs strongest blocks..but man are they awesome!
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I love my 377...but I can tell you. I wish it was a 406 haha would be great in a roundy round car or road race. Trucks need the all the torque they can get sqaurodynamics you know
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[86shorty]

Originally Posted by INSIDIOUS '86

I love my 377...but I can tell you. I wish it was a 406 haha would be great in a roundy round car or road race. Trucks need the all the torque they can get sqaurodynamics you know
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Baha! Yes..the squareodynamics do need all the help they can get I'm meeting the guy tomorrow to take a look at the block. Said he'd feel more comfortable holding it for me if he met me first
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[BigBlocksRule]

"509" castings are not all created equal. They were heavier 'till about '75 - '76 when they shed about 10 - 15 lbs. I have one of each, differences are visible on the engine stand. I wouldn't hesitate to use either.
Unless it's a race-only deal, pretty much any 2-bolt 400 will do.

[bnoon]

I stroked a 2 bolt 400 block (added 4 bolt splayed caps) out to 420 inches with 5.7" rods back in about '96. With a BIG roller cam and ported Trick Flow 23 degree heads with 2" headers it made 510 horsepower and right at 500 TQ at the wheels in my '70 Vette. That was at Car Craft Summer Nationals in MN on their dyno shootout. I made more horsepower and torque than the big block cars for dang near the whole day! Til that dang 502 showed up LOL!

[86shorty]

Well todays the day. Any advice what I should look for in the block? U guys want pics? Lol
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[KQQL IT]

Pulled threads and cracks around the head bolts.
And a chance to magna flux it
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[RPOZ11]

Originally Posted by KQQL IT

Pulled threads and cracks around the head bolts.
And a chance to magna flux it
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X2

This is a correct statement!
Check for these signs!
Sometimes you see the cracks on the block side of the main saddles towards to pan rails of that area.
Check the steam holes for cracks between the cylinders with the heads off.
As KQQL IT said, magnuflux these areas before spending any money on it.

[RPOZ11]

I have a few of these blocks, all standard.
The hype on the 4-bolt main blocks is true, but thats if you are pushing the limits on it.
I have always suggested that these blocks are fine.
Build it as a street motor.
9-10.1 compression on pump gas, drive it as a daily driver and get on it as you wish.
Over revving it can cause stresses to the mains and especially the rear main cap.
Imagine the load pushing up on the rear main when jumping on & off the gas often.
The load forces on the rear main I believe is what causes the main caps to move/flex.
Then you have the engine running up & down the rpm ranges.
Forces in both directions ask the energy to be displaced somewhere.
Abuse it and they can break.
But I feel that street racing, drag racing, or too much HP without supporting the mains is why the 4-bolt main blocks fail.
If you are finding a stock bore 400 4-bolt block, why is it available for a rebuild?
Because it sucessfully survived the lifespan GM intended of it in a street version.

You should be fine.
People hype these up as undesirable.
Its a misnomer.
Build it for your truck between 9 & 10.1 for street use, and enjoy it.
Drive it intending it to last for you.

[86shorty]

Its the 2 bolt main 509 block. Ill check out all the mains and head bolt threads. Its in his storage unit which ill be at around 3 pm today. Ill see if it has been magnafluxed and the overall wear on it. My intentions for it are as a strong driver. Its going to be a slow builder. I fully intend to put the money in the machine work . Ill be putting 4 bolt splayed mains on it too. He says it was his extra block and he had built another 2 bolt before he acquired this one. I won't he buying today..but in a couple weeks when ill have the wiggle room for money. It is JUST the block. No heads or anything
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[RPOZ11]

Originally Posted by 86shorty

Its the 2 bolt main 509 block. Ill check out all the mains and head bolt threads. Its in his storage unit which ill be at around 3 pm today. Ill see if it has been magnafluxed and the overall wear on it. My intentions for it are as a strong driver. Its going to be a slow builder

The 509 Block is your best start.
Hopefully it's still standard bore.
I built up 2 of these, one a 509 & the other a 4-bolt 511 block.
I used 993 heads on the 511 with 2.02/1.60 valves and a hydraulic 510 lift cam.
The 509 I had was internally balanced with a set of 034 BowTie heads.
This one I sold locally and is still cruising the streets here.

Tell us what your pars will be for this 400!

[INSIDIOUS '86]

You can't take the four bolt and then splay the mains the material is just not there to do it

I call 400s poker engines for a reason. Cause you put in money to see of its any good and alot of times you lose. Which means you have to keep playing.
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