SB350 vs. SB400

[trev1981]

383's are good but 400's are better

 

[Ancient4X4]

Wow, this thread really makes me wanna build the 400 in my truck.

People are always putting my truck down as an old piece of junk, but I know better.

 

[Hogback Fabrication]

383's are good but 400's are better

I would beg to differ, which is why I chose a 383 over a 400. The 400 block is not nearly as well designed and is much more failure prone. They like to crack, especially the 4 bolt mains.

Add in that fact that you have to drill steam holes in the heads (which makes them want to crack easier) and I chose to stick with the 350 block.

 

[tiger9297]

I would beg to differ, which is why I chose a 383 over a 400. The 400 block is not nearly as well designed and is much more failure prone. They like to crack, especially the 4 bolt mains.

Add in that fact that you have to drill steam holes in the heads (which makes them want to crack easier) and I chose to stick with the 350 block.

I'm just finishing up a MPFI 383 for my '90 K5. I could have gone w/ a 400, but chose to stick with the 350 block for the same reasons. Reliability is a big issue with me as I use this truck to tow my camper /travel with the family on board. I can't have an engine that, at best, is questionable when I know the 350 block is a solid foundation. I agree the 400 has the potential to make more power than a 383 for obvious reasons. However, I do not think that the small increase in power is worth giving up the 350 block. That's just my opinion of course.

On another note I went with the Vortec heads for my 383 and I have to say I'm impressed that the Vortec heads outperformed the AFR's down low. It seems that for a truck (low RPM/high TQ) engine the Vortecs are hard to beat at any price.

 

[Ancient4X4]

I always hear about the 400 being prone to overheating, but I've never had the problem myself. The only time my truck has overheated in its now over 30 year history is when the original radiator finally gave up the ghost about four years ago. The original radiator was no good from the factory and he took it back and they had welded it back together under warranty according to my dad.

I shut it down right away a couple times when I noticed the temperature climbing. And that's an understandable failure I think, no coolant and all. It has always run nice and cool even when it's been driven in 110+ degree weather with the air running.

I have heard something mentioned about it lacking rear cooling fins or something like that. That's obviously not a good thing, but I've not had any problems myself. I'm sure the 350 is a more reliable design when all is said and done and that is taken into account. I'd rather have the extra displacement though myself.

 

[Shawn]

For those that say the 400's aren't reliable, do you have any proof of this???
Most important thing to do with a 400 sbc is to get the block sonic-checked and don't over bore if its not needed. Most engine failures happen from inproper build. It happened to my old 350 and my 496.

I know the 4 bolt 400's aren't good for racing because of the main webbing.

2 bolts are the block you want and then you just splay it to 4 bolts which is even stronger than having 4 bolt mains. The steam holes do not cause problems with cracking or overheating. If that was the case, nobody would be using a 400.

 

[Ancient4X4]

I've got a question, how can I tell if my engine is a 2 bolt or a 4 bolt? And what's bad about the 4 bolt engines?

Thanks

 

[Shawn]

2 bolt 400 blocks have thicker main webbing, so can take a bit more stress. I'm sure a 4 bolt will work fine if you're not running nitrous or supercharger/turbo. Sorry, didn't mean to imply that 400 4bolts were horrible, I was just thinking for my supercharged application.

I think a 3951509 is a 2 bolt
and a 3951511 is a 4 bolt.

 

[Hogback Fabrication]

The 4 bolt 400 main caps are notorious for cracking. The 2 bolts actually hold up better.