My 72 came with a non-stock sb 400 from a gmc truck of the same year. Now I was going to pull the engine out and replace it with a 350 since thats what the car originally came with,but every mechanic I have talked with told me to hold on to the 400 because they are rare engines that can produce a LOT of horse power compared to a 350. So I am going to keep the 400 and build it up to be as powerful as it possibly can. I myself won't do this,but I know a engine shop that will pull the engine out,rebuild,and install for around $1000 to $1500 if I buy the parts. So my question is,what are the parts (rings,bearings,intake,heads,etc.) best for achieving my goal? I would love to see this car have more than 400+ HP, possibly 600.

 

A couple of things I must point out....
1. The 400 heads and block have steam ports along side the cylinders, the heads on my 400 developed cracks at these ports, and I understand this to be quite common. [&o]

2. Take the crank out of the 400 and put it in a 350, and build from there. You CAN get 600hp from a 350, just depends on how you build it. I believe the 400 block to be over rated.

 

The 400 also had siamesed bores which could cause cooling issues. If the 400 is a 2-bolt, then probably not worth the investment IMO. Good luck.

 

And a lot of pickup truck 400s were 2-bolt mains. Weak block to build a powerful engine on.

 

The 400 I had, came out of a 1 1/2 ton truck. It was a 4 bolt, and it had the cracks. I agree with Lee and 73shark!
I recomend that you use the 400 crank though. A 400 crank in a 350 4 bolt?........................Yooooouuuuuu bet cha!!![sm=icon_rock.gif]

 

Is that what gets you a 383?

 

I'm not sure about what the c. i. are, but we used to call it "strokin' a rat". If ya "Stroke a rat", I'll go like.......rhimes with...swell!
I'm guessin that you would need to bore too, 30 over, to get the 383.

 

good evening 72stingray: I see you have not recieved a clear answer about rebuilding your 400, GM say's that a 2 bolt block can support 500 horsepower, so if the main components ( block, crank, heads, rods ) are ok, then I would rebuild as a warmed up 400. If the block is unuseable and the crank can be turned down ok to fit the 350 journals, then you can build a 383 from the 4.00" bore and 3.75" sroke, or a 385 if you have to bore .030" over. Try to stay with the longer stroke of the 400 crank in order to produce higher torqe, big torqe numbers are going to give you quicker acceleration better than big horsepower numbers will.

 

I think he got a pretty straight answer, just maybe not the one he wants.

I seriously doubt a 2 bolt 400 will do a good 500 HP and would never put any of my money into one - they crack, they flex, they leak . . . . they are a good low RPM torque engine, but not a screamer. Putting that 400 crank (if it passes good condition tests) in a non-siamesed bore 4-bolt 350 to get around 383 cubes is by far the preferred approach. Its a far stronger block and many more types of good heads will fit it -- it is the most hot rodded engine and there are gobs of choices for parts -- not so the 400.

 

Lee Willis, I agree with you on everything you commented on about the 400 block, I would much prefer to use a 350 block for a build up, just thought we could save money for 72Stingray if he has some good parts in the 400. He's at least getting a good education on SBC motors.