Team Chevelle banner
1 - 12 of 12 Posts

·
Registered
Joined
·
119 Posts
Discussion Starter · #1 ·
I just bought a complete (carb to oil pan) 400 sbc casting #3951511 complete engine from Craigslist for $500. It's a 1971 265HP version out of a 1971 Impala. It has the original heads on it that I've heard are crappy for performance. They are 76cc chambers. It has a Pete Jackson gear drive, Blue Racer 1.6 Aluminum roller rockers and some kind of performance cam. I haven't pulled the pan to see if it's a 2 or 4 bolt yet. I have a fresh set of camel hump heads that I was thinking of putting on it after I have the steam holes drilled. I'm only looking to make around 400-450hp. What rods and pistons are good for it? I'm on a low buget and have lots of 350 parts laying around. Can I use some of them in this motor? Thanks for any help you can offer.
 

·
In Memoriam
66 El Camino 57 Chevy pickup 2004 Tahoe
Joined
·
29,419 Posts
be sure you understand what the compression ratio will be and what kind of gas is available before you put small chamber heads on a 400.

The 511 block is fine, that's what I have in my car.
 

·
Registered
Joined
·
236 Posts
Mines a 511 block. It's a 4 bolt for sure. I run four notch flattops with AFR 195 heads with 74 cc chambers and have 10.1:1 cr static. If I was to offer any advice, and your stock lower end is OK, use it as is. It should be fine for 400 horse or so, and any stock head you put on it will keep the power levels down for sure.

Find a decent set of pistons that will get your compression level to around 10:1 and run a 280 degree hydraulic cam, and you'll hit your 400 horse target easy.
 
G

·
I just bought a complete (carb to oil pan) 400 sbc casting #3951511 complete engine from Craigslist for $500. It's a 1971 265HP version out of a 1971 Impala. It has the original heads on it that I've heard are crappy for performance. They are 76cc chambers. It has a Pete Jackson gear drive, Blue Racer 1.6 Aluminum roller rockers and some kind of performance cam. I haven't pulled the pan to see if it's a 2 or 4 bolt yet. I have a fresh set of camel hump heads that I was thinking of putting on it after I have the steam holes drilled. I'm only looking to make around 400-450hp. What rods and pistons are good for it? I'm on a low buget and have lots of 350 parts laying around. Can I use some of them in this motor? Thanks for any help you can offer.
Yes its very good for your application, I would have NO problem using that block.
 

·
Registered
Joined
·
3,636 Posts
There are only 3 400 block castings; 511, 509, 817. The 511 is the early one (70-72), the 509 & 817 are the later ones.

The later ones are possibly "better", which is NOT the same as saying that the 511 is "not good". Maybe, just not quite as good, for SOME things. But for a street or moderate racing application, it's not a significant difference, and I wouldn't let that bother me if I was you. For a budget hot street motor it'll be perfectly fine.

It'll almost certainly have factory 4-bolt main caps installed on it.

The later blocks had more metal around the main webbing area, so they're "stronger". People talk about "4-bolt" vs "2-bolt", but that's not really the difference; the # of bolts is incidental. It happens that the factory put 4-bolt caps on the early ones and 2-bolt caps on the later. But the REAL difference in the blocks is early vs late, not 2- vs 4-bolt. The bolts themselves aren't what makes the ones "better" than the other.

Yes the heads that came on 400s are absolute crap. If it still has the original heads, throw then in the trash, they're pretty much hopeless; and get something decent. Vortecs wouldn't be a bad choice. Other than that, you pretty much need to go to the aftermarket. Double-humps are marginal at best. If you use them, be sure that they have the accessory holes in the ends, if your car's accessories need them, as anything from 69 up will; it's nearly impossible to fake those holes. You can't just "drill" them in heads that don't have them, because there's nothing there to drill into.

It's VERY VERY easy to get 400 HP out of a 400, with the right heads. Hard to avoid getting that much in fact. A Comp XE or a Voodoo cam in the 224-230° kind of range, NOT a Summit cam, "RPM" cam, or any of the old stock cams like the 151 or other similar garbage, are the best choice with Vortecs or other stock heads, or even alot of the aftermarket ones. The large CID needs the added exhaust flow from the larger exh lobe.

Yes, virtually all 350 parts will fit a 400; the specific exceptions being the crank damper and flywheel, if you stick with the factory "external balance" stuff. Also you'll need to drill the steam holes in the heads if they don't already have them, which you can do yourself with a hand drill, no sense in paying somebody else to do that if you don't have to or it's not just a matter of convenience (like, they're already doing some other machine work, and you get them to do that at the same time).

OTOH, "fit" is not the same as "is the right thing". Remember, you're dealing with a motor that's on up into the big block cubes range, so all of the parts have to be chosen to support that kind of size. Stuff that's borderline radical in a 350, tends to be mild street stuff in a 400.

You'll get best results with a small chamber head (64cc) and pistons with a small dish or (ideally) a "reverse dome", to put the ACTUAL CR (calculated including the ACTUAL MEASURED deck clearance) in the high 9s if the heads are iron, or mid 10s with aluminum heads. Deck clearance is CRUCIAL: don't be fooled by the "catalog" CR listings, or just "assume" that there is no deck clearance. With most "rebuilder" type pistons including TRWs for example, the deck clearance, which is how far "down in the hole" the pistons are at TDC, can be nearly .050" in some blocks, which in turn can cause the ACTUAL CR to be a full point lower than some randomly guessed and "calculated" CR. Any CR calculator is only as accurate as theh numbers you put into it.
 

·
Registered
Joined
·
119 Posts
Discussion Starter · #6 ·
Wow, I didn't know that I could drill my own steam holes in the heads. If this motor is stock and all I do is add the camel humps 64cc, what comp ratio will I have? Thanks for all of the help.
 

·
Registered
Joined
·
1 Posts
i got a 3951511 400 from a buddy that i am putting in my truck. The only question i have is, i ran the casting number and it says its a 4 bolt main, but its clearly a two bolt. How can this be, i have cleaned the block and the numbers are correct.
 

·
Registered
Joined
·
3,636 Posts
How can this be
Ummmm.... trick question?

The factory only put 2 bolts in the center 3 main caps. ;)

Seriously, alot of the over-the-counter service motors came set up that way. Early block casting #, but only 2-bolt caps. They must have realized that the extra 2 bolts were pretty much worthless; basically, a solution to a problem that didn't exist. Kind of like, if you build a house, you want it to be strong, against the hazards that exist locally; so if you build a house in LA you build it to withstand earthquakes and don't worry about hurricanes, and vice-versa if it's in Florida. Those extra bolts are like that: a solution to a problem that will never happen anyway. The cast crank pretty much guarantees adequate protection against stresses to the block of sufficient magnitude that the bolts make any difference. Extra cost, no benefit: an extremely high cost/benefit ratio.

Also, the early 400 blocks mostly had 3 freeze plugs in each side of the block, unlike all other SBCs including later 400s that only had 2. What does that block have? (I'm gonna guess, strictly a guess, 2)
 

·
Registered
Joined
·
951 Posts
but its clearly a two bolt. How can this be
Many years of mis-information being spread on the internet maybe?
Until the pan is off, don't guess how many bolts there are.
I've gone 9's with stock 4 bolt main 400 blocks on nitrous, and never hurt anything. Never ran steam holes on any of them either, and taken 1000+ trips without ever going over 190° in traffic with 117° weather.
About 99% of the stuff you read about 400's is BS!
 

·
Registered
Joined
·
335 Posts
bigbird,

Is it safe to assume you don't want to do any machine work on it? Because if you did, I ran a Summit engine kit for years that had 14cc dish forged 400 pistons. The kit was dirt cheap and works with the stock crank and rods. I ran the Edelbrock Performer RPM cam (don't believe the hype, that cam works great in a 400), Sportsman II heads and an RPM intake. It made great power and torque just be sure to shift at 6000 or less.

Do some more research on what your comp would be with the double hump heads. The 400 came with a dish piston but that may not be what is in it now?? Also, my left bank was 35 in the hole and the right was 38 before I decked it.

I have a buddy running 7.0s in a 70 Chevelle in the 1/8th with a 421 based on a 511 block. They work great! Have fun!
 

·
Registered
Joined
·
11,895 Posts
I think I saw that one on CL awhile back, only wanted the block though.

Bring those camel humps over here, getting em to flow better is no problem.
400+ should be doable .

How far in LA are you?
In the sfv here
 
1 - 12 of 12 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top