Thoughts on sbc 400 casting '817'.

[Scott Liggett]

I found a complete sbc 400 in the junkyard. I am only interested in the block in order to start building a new short block for the Impala to put some real boost through. It rotates freely, but since it's untouched, I don't know what shape it is in. I can get the block for $75, the short block for $175.

It's a casting number '817' 400 4 bbl, 175 hp. Suffix code is CSX. Two bolt block.

My plan would be to slowly put it together as funds came along. Short fill the block, machine it for splayed four bolt main caps, get a forged crank, rods, and about 8.5:1 pistons. Either build it as a 406" or 420".

I know the 509 two bolt blocks are good, but don't know about these.

[Barry Donovan]

I had to witness my bro n law tortured by a 400. The bottom end is not even as bad as the siamesed bores.(blows chunks at the top, right rear). The ld seals, crank pushing boundaries, not even pcv is normal. Save the pennies go LS anything...buy pieces at a time. The 400 is a sad stab at something economical excuse...like most of the 70s. Did you know the only success for the 400 was a direct fan in a van engine compartment? leaving the tiny hp numbers alone of course. All else.. not a single success...except Maybe a freak in Arizona.

[yellomalibu]

I don't know about casting numbers, but I'd try it for $175.

Wait, is this for the turbo motor? If you plan on making too much horsepower for the stock crank, I would pause and consider an aftermarket block, too. I'm not sure if I'd go with 40 year old stuff for high horsepower, but I wouldn't hesitate at all to buy it and have it checked out by a machine shop to use for a mild to moderate motor.

I'll look at my car in a bit to see what casting number it is... I do know that I'm using a stock crank, and the motor has made enough horsepower to push my car to 10.97 @ 119.9? mph, and have spun it 7200 rpm.

*edit* It is an 817 block in my car now... and thinking twice, this particular block isn't the one that went that fast. The crank is, however.

[Scott Liggett]

I'm going to a SCAT forged crank. I can buy them through work cheap.

I'm thinking 750 hp is the limit with a hard filled block. $2000 for a block isn't in my budget.

[Beagle]

I'm going to a SCAT forged crank. I can buy them through work cheap.

I'm thinking 750 hp is the limit with a hard filled block. $2000 for a block isn't in my budget.

2000 for a block that still probably needs finish machining... ? Does your company let you use the machine stuff for your personal junk?

[Scott Liggett]

2000 for a block that still probably needs finish machining... ? Does your company let you use the machine stuff for your personal junk?

I haven't asked yet. It's more a production line type of engine building; but they do have the ability to change engine types easily. I'm sure the plant guys like change of pace. They would enjoy doing some custom machining now and again.

[TheSilverBuick]

Better is a myth, it's still a chebby

From what I've read as a mostly non-interested observer is there isn't any real difference but get the bores sonic checked first then go from there. If the Chevy's are like the Pontiac's the 2-bolt blocks are preferred to be upgraded to 4-bolt by a competent machine shop.

[Deaf Bob]

400's get a bad rap, why...don't really know...
We have ran 3 different 400's over the years.. One would seize up if it got a little warm (cheap assembly line rebuild) the others were exceptionally good ..
Guess it is that way for ANY block..
As long as it checks out.. Go for it!
With all the aftermarket has for the Chevy small block, it'd be real hard to build a flop... Especially by you!

[Scott Liggett]

Better is a myth, it's still a chebby

From what I've read as a mostly non-interested observer is there isn't any real difference but get the bores sonic checked first then go from there. If the Chevy's are like the Pontiac's the 2-bolt blocks are preferred to be upgraded to 4-bolt by a competent machine shop.

The 400 4 bolt blocks had a legitimate weakness. The main webbing between the crank and the cam was windowed. Weakened the block severely. Why they are avoided by racers and the like.

After market splayed caps really strengthen the lower end of the block when the crank is spinning above 6000 rpm. Two bolt blocks are easily upgraded to these. Four bolt blocks are not able to be upgraded to splayed caps.

[Dan Barlow]

Just my two cents. I had one 400 sbc I loved it when I replaced a then 7 cylinder 350. Made the big blazer just zip around like a sports car. Till it developed a knock. Back then you could pick up SBCs in our trader paper for $100-200. So I decided to see how long it would run. 36 miles was it for those wondering. I think I would rather give up a few cubes and do the 383 thing with a less prone to over heat 350 block. Especially if your going to really boost it. That's all I got.

[BOSSMAN]

Scott I've been there and done that. If you plan to make a decent amount of power my suggestion to you would be to get a Dart SHP block (or a Blueprint one since you work there). Not just the main webbing is weak, the deck is probably worse. I've pushed the limit of these blocks on my own stuff and it just isn't worth wasting the money and crossing your fingers in hopes it will live. Do yourself a favor and get an aftermarket piece if you plan to invest money on a new rotating assembly.

[kyhunter89]

817 is strongest, followed closely/tied with 509. 811 is the only four bolt main, if I remember right. Mine is a . You might want to mention your end goal turbo/head wise and go from there.

[Orange65]

I tried to save some money using a stock block on my last build. I bought a used RV engine that had less than 100K on it and ran (burnt valve but I didn't want the RV heads). I then did just about every machining operation you can do to the block because it needed it. (Have you priced sonic testing boring, hot tanking, new cam bearings, new freeze plugs, decking, installing new main caps in your case and align boring a block)? In the end, I might have saved $300 over a Dart block. As Forrest Gump would say- "A used engine is like a box of chocolates, you never know what you are going to get." Save your change until you can get an aftermarket block. It is worth the piece of mind plus later on when you get bored with 600 HP, you can turn up the boost and not worry.

[yellomalibu]

Hard to argue with that... but a standard/standard/standard short block is definitely worth having for a future build (or trading material). I would buy it if I found one available for the price you mentioned.

The stock stuff is great for several applications, just not sure if a "power adder" motor is one of them.

[Caveman Tony]

anyone see this month's PHR?

2 bolt 400 build for EM.