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SBC 400 build

7K views 16 replies 12 participants last post by  Busted Knuckles 
#1 ·
I have built a lot of motors but never a 400. Would you use a 2-bolt or a 4-bolt? Wanting to make about 525 HP. At what point is a stock 400 block good to? HP wise.My budget doesn't allow an aftermarket block.I have seen some 434 rotating assm for as little as $ 1400. Build a 434 or a 406? How about cam and head selections? I have about $ 3000. to build the longblock. Would I be better off to wait and try to save some more money? I know a lot of questions but I want to do this once and not make any mistakes. I appreciate any help. Wayne
 
#2 ·
I used a Dart SHP block, paid around 1200 dollars for it. The rest is in my signature. Very pleased. By the time you buy an old block,have it cleaned,tested and machined you wont be too far off using the dart block. Good luck with your project. Mike
 
#3 ·
Wayne. What do you want to do with the 400, good street motor or mostly track motor? 383,s and 400,s are funny . They both can get real pricey real fast depending on wich route you take. You can build them real good without overkill for reasonable money , or you can spend a ton of cash. The power comes from good heads but there can be overkill there also. The lower end needs good machine work , but you can get overkill there also . It comes down to what,s necessary and what,s not. Wich way do you want to go spend the 3 for acomplete motor or twice that. Alex:D
 
#4 ·
Wayne,

I have a 400 that made 548 hp with a factory crank, factory 5.7 rods and hyper pistons. It also took quite a few 100-150 hp hits of nitrous, never any problems. Mine is a 2 bolt and was still when in the 406 configuration.
I think with a factory 400 block, if it checks out okay, is good to about 650 hp. Beyond that imo things get a little dicey.
I am making mine into a 434 and when I get back on that project I think I will bite the bullet and get a dart block. The dart piece is certainly a better piece, better ring seal and longevity for sure.
 
#5 ·
ss27, I am building this for a 68-72 chevy truck or my 69 camaro. I have this problem, a buddy of mine for over 40 years is a ford guy and he has this mustang. In my 69 camaro I have a 383 with Trickflow 195 heads , solid roller that made 485Hp and I outran his mustang with his built 306 and him using a 75 shot of NOS. Now he has built a 331 with some high dollar parts and I changed my car from 410 gears to 355. So I am worried that he may out run me now. I ran an 11.76 to his 11.88. the last time we went to the track in Tulsa ok. So, I want a 10.5 compression motor that will make about 525 to 550 HP. I just can't let him run a better time cause he will needle me forever. So there is my dilemma.. Wayne
 
#6 ·
2-bolt 400s are stronger than 4-bolt so go that route for sure. If you get a good 400 block they can take a pounding. I would not build a 434 with a factory block though.

My thoughts are, if you have a 383 already spend some money on it. Get some head work done (or a new set), cam, intake, whatever. It will be a bunch cheaper than building a 400 from scratch.

A good converter can pick you up as much as a good set of heads some times....
 
#7 ·
Spend the money on what you already have if it's running good. Head work and a cam change to work with your gear change, then a good tune. 525hp out of a 383 isn't exactly a far reach.

Here's a 383 rear wheel dyno from a member on one of the Corvette forums from a couple of years ago comparing a set of hand ported Trick Flow 195's (blue line) to a set of AFR competition port 195's (red line) out of the box. If you are running out of the box Trick Flow's then you can see that you may have some left in them by just having someone work them over.

In his thread, he initially had worse times after the head change and it just ended two years ago without updates. However, his signature shows his times at 11.37 whereas his best time with the Trick Flow heads was 11.98. Didn't search around to see what he did between the last post in his thread and his current signature time.


 
#10 ·
i would agree with alot of these comments--i luved my 406 2 bolt 548 on motor and had over 120 runs on 250 shot with no problems --i tore down that set up and built a 434 with it but i will never do it again--there is not enough clearance i spent weeks grinding on it-even had to grind off corners of rod cap bolts to clear cam and thats with a small base circle cam--.032-.039 clearance all around--it ran 5.60s in 1/8 with alot of juice and didnt blow but i sold it before it would--now a 421 is a different story-it will work-and 650hp is easy at 3000 in parts but you still will need good machine work
 
#11 ·
As said above the factory 2 bolt is said to be stronger than the factory 4 bolt.

Also the Dart SHP would be better than either of the factory blocks and once you figure in machining it's a wash...some selling 400 blocks are getting very good $$$ but a lot of 400's don't pass the sonic test.

I'd say save a few more $ IMO
 
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