I am looking for a well built, reliable SBC 400 Short block to install in my car,....no racing, street driving only. Want it built for low RPM power......for fun back roads canyon carving in Vette. Not interesed in a High RPM HP engine.....I just want more than teh 180 HP L48 in my basement. Will be topping with AFR 195 street heads, Mike Jones cam, Edelbrock intake, and Holley DP. Considering a couple large places, like CNC Motorsports,....etc. Any recommendations?

 

Why a 400 and not a 350? A 350 can give you plenty with the right build,lots easier to find with many different levels of build available in short or long block crates.
Keep in mind if you do go with a 400 you'll need a different flexplate or flywheel,externally balanced.

 

Not sure how much of the 400's background you know. They were a cheap way to get a powerful SB that is a bolt in replacement for an existing motor. This mod was very popular with street guys and some circle track division that required "stock" motors. This made the 400's hard to find by the end of the 80's. At first it was just the 4 bolt main ones that were hard to find then it became all of them. Guys were buying running and driving cars just to get the 400's out of them. The 400 has a design flaw due to the block size. There is not enough distance between the center cylinders for a proper coolant passage. This makes them prone to overheating at that spot and it limits the amount the cylinder can be opened up. This means if you buy a 400 with some miles on it and you go to rebuild it may not be fixable and it will be even more prone to overheating. Yes you can keep them cool but you need a much better cooling system then you would need for the same HP 350. The scary part of buying a used 400 is you may get one that burns through head gaskets because of over boring or any boring on a block with defects. The SB 400 is the definition of "buyer beware". I would only buy a used one if I could see that the head was not off for a long time and I could run it and test for hydrocarbons in the coolant system.

IMO you are better off with an aftermarket 383. The 383 has the stoke of the 400 and the bore of a 350. Your L48 is still the same block the factory built 300hp engines from. A good 383 forged stroker kits are some of the most reasonable cost kits you can find. When the 400's became hard to find many race teams moved to the 383. This caused high volumes to be made. On any given race night at your local track half the cars could have 383 kits in them. Most race teams would never switch back because of the head gasket issue the cooling flaw in the 400 caused. If you can find an older builder who has done a bunch of these it would be worth the money to get the kit he recommends and let him put it together. You need to verify clearances and there are possible casting defects to look for. I say older guy because most modern engine builders do LSX and LTX stuff. Rightly so. The LS by design can handle way more HP than any SBC GM built.

If you keep an eye out you may be able to find a low miles used 383 from someone upgrading to a LS engine.

The only reason your L48 350 if low on HP is compression. A set of pistons can fix that. No reason that with 9.5:1 pistons the head change you mentioned and right CAM you would beat the stock SB 400 in every way. Even with the tame CAM you would be well over 350 HP and you could still beat the 400s torque and have a more dependable engine.

 

I would not build or buy a 400 SBC with a factory GM block. I have the money to buy a Dart SHP block, with AFR 195 heads. So....while I am not a rich guy, I have the money to buy good parts that are better than factory. I restored / rebuilt my Corvette to far higher standards than Chevrolet ever dreamed of when they built it,....and I spent many times over what I could sell it for. So....point is, even though I am not racing, I want the car to be strong at low RPM,....so on the street it drives differently than my wife's Toyota Camry. Is a hobby car....that is my dream car....and I spend the money it takes to make it something special to me.

The idea of resurrecting the L48 is going to come up short to what a well built Dart block / AFR head strong engine would be. I can't believe that all I need to do is stroke and piston an L48....and its the same as the 400 I want to build. They can't be the same. Hell....I have a 2006 base model Corvette....400 HP / 400 lbs torque from the factory.....and I don't think it really is that impressive....and thats an LS2. The engine I want in the C3 Corvette will be something quite different and better......and if not, why bother.

 

Well whatever floats yer boat but I'm with Gorn on the 383,otherwise do an LS restomod IMHO.

 

Ok,.....dropping price on the VortecPro engine to $6000........I need to pay for the new stuff.

 

Absolutely no interest in an LS engine in my C3 Corvette

 

I miss understood when someone says small block 400 I think of the GM small block. The dart block can be just about any size you want it to be. If you want torque and you are not going to supercharge it there is no replacement for displacement. Dart make both LS and SBC blocks that can go up to 427 Inchs.

The block adds no HP to the engine. It is a supporting mod that allows the other parts you buy work as they should. The Dart block will not flex or fatigue over time like a stock one will.

What we consider the modern carburetor was designed in the 50's. That is a lot to ask for that design to be better than a modern fuel injection.

Why mess around with a short block? Why not just buy a complete engine? You can buy a 383 with a warranty and close to 450 HP for under 6K. I like Pace Performance They have it all Short, long and complete. Small Block | Pace Performance

LS is a better design engine block. Don't take my word for it call Dart and ask their support staff. The Y block design and the 6 bolt main can support up to twice the torque of any Gen 1 SBC design. That assumes we are talking like quality blocks. Cast vs Cast or Custom Cast vs Custom Cast.

 

whatever you go with post up some pictures. we want to see your toy....