About to buy a 400sbc - what to look for?

[sixnine]

I'm going to look at two Chevy 400 small blocks tomorrow. One is a two-bolt main, but is a high-nickel 509 block. It is a short-block minus heads and intake. The other is a 4 bolt main bare block. Both blocks have original bore sizes. Is the high-nickel block worth taking over the 4 bolt block? Also, this is my first used engine purchase - so what should I look for? The 400s were prone to cracking (I think?) where should I look to see if either are cracked?

Thanks in advance for any advice.

[Rreemo]

Check in the top edges of the cylinder walls for cracks...they are prone to getting small hairlines up there. You'll also want to inspect around the main webbings really well.

[Sinister]

I've heard on another forum that the 2 bolt 400 blocks are stronger then the 4 bolt ones.

[Longhorn Man]

the 2 bolt IS stronger, but in street trim it's all moot anywyas. You won't be reving it over 6000 so it doesn't matter.
And if I am wrong, and you want to make tons of power and rev the snot out of it, the 2 bolt is the way to go, then put splayed caps on it.
I've never heard of a 10-20 (high nickle) 400 block... but if it is true, high nickle is the shiznit.

[wibilly]

also check in the lifter valleys for cracks and i would also take a 2 bolt block over a 4 anyday only one i ever seen brake in main webs was a 4 bolt. splayed 2 bolt is way better but not nessary for a street engine

[special-K]

How much are these?I`d get both.I`d keep athe 2-bolt 509 block over the other.

[Billla]

The first question is are they selling the blocks "as is" or "rebuildable", i.e. they're not cracked.

I think everyone nailed the big rocks - be sure to bring a vernier caliper to ensure they're standard bore.

[sixnine]

The guy who has them for sale swears they are virgin blocks - original bore sizes, no cracks, ready to rebuild. I'm going to look at them this afternoon, so I'll see. The price is decent enough that I might buy both of them if they are as advertised.

I'm along way off from being ready to build a new engine, but I've always wanted a 406 and these blocks are getting harder and harder to come by in rebuildable form and they seem like a really good deal.

[Billla]

Originally Posted by sixnine

The guy who has them for sale swears they are virgin blocks - original bore sizes, no cracks, ready to rebuild. .

So he should have no problems giving you your money back if they fail the pressure/mag test - right?

[bigsnookmaster]

I will tell you,once you go to a 406,you'll never want to go smaller again.I've had them for about 15 years.A good set of heads,and the right cam and these things will boil the tires with no problem.They work good with3:73 gears and a good exhaust.Good luck.

[milled]

You could always go for the ls-6 new gen small block with 6 bolt mains, they walk the dog!

[sixnine]

Originally Posted by bigsnookmaster

I will tell you,once you go to a 406,you'll never want to go smaller again.I've had them for about 15 years.A good set of heads,and the right cam and these things will boil the tires with no problem.They work good with3:73 gears and a good exhaust.Good luck.

Thanks for the input. What do you use for heads? Do you run factory castings? What about Vortecs, will a 400 block accept those?

[Sinister]

Vortecs will work, but you have to drill steam holes.

[cobb_ben]

I like the 400 destroker. The 400 with the 350 crank and 6in rods, its like a 380cid. Lots of fun! And a lot faster reving then a 383 stroker. Just my $0.02

[bigsnookmaster]

My last 406 had World products Sportsman II heads,Comp cams X-treme hydraulic cam,.507 int..510 ex. With flattop pistons and a 650 dbl.pumper.It went 13.15 in the quarter on motor,the way I drove it everyday.12.49 at 113mph. on a 150 shot of NOS. At 3950lbs. with 275/60-15 radials.Not bad.If you got a few bucks,get the aftermarket heads,but fuelie heads with some pocket porting work pretty well also.