400 sbc

[redneck_reed78]

What is the general opinion on these motors? I don't see them around much but I am looking at a lifted 86' with a 400 in it and was wondering if these are anywhere near the same animal as a 350? Should I stay away from it or is it a good engine? I heard something about cooling problems on them. Seems like the 6.2; people love them or hate them. What kind of power can I expect? Finally, could a 400 be had factory in a 1986 K10? Something in me wants to say that was only 73-80 in the squares? Also what would be involved in sticking a tbi off of an 88 suburban 350 on to this engine and would it work? Thanks! Sorry for all the questions just don't want to invest in a money pit.

 

[CSFJ]

The 400 disappeared from the option list sometime in the 70s. They interchange part wise with most other small block stuff, with a few exceptions. The heads have steam holes that the other small blocks didn't. So you could run 400 heads on a 350, but not the other way around, unless you drilled some holes. The harmonic damper is different, as is the flywheel/flex plate if I remember correctly. The cylinders are siamesed (sp?) which can cause some overheating issues if they've been over bored too far. Otherwise, they're a good torquey engine.

 

[Georgeb]

I had one in a 79 pickup for a while before selling it to my uncle. Nice motor!

 

[Handy Andy]

400 sbc's are good motors. As stated by others, the 3/5 and 4/6 cylinders are siamesed cylinders which could cause overheating issues if the motor has been bored more than about .030. The addition of steam ports in the heads help to eliminate the problem. What happens is the siamesed cylinders basically trap coolant next to them, which in turn causes the coolant to heat to the point of turning to steam. Steam does not cool anything very well, so you could end up cracking or warping the deck and cylinders causing major problems. Drilling the steam holes allows for coolant to flow past the siamesed cylinders keeping them cool. From what I've been able to find it's generally not a problem unless your going to be turning a ton of rpm's for a fair amount of time (circle track racing).

I am currently building one for my 86 sierra 1/2 ton. The block and crank are at the machine shop being checked and worked over. I'm building mine more for pulling my boat behind my squarebody so it will have more torque throughout the lower end of the rpm range.

If i'm not mistaken they only made 400's from 1970 to 1980 and from what I've read they were pretty close to the same performance as the 350. I think the 400 generally had abut 10 more hp in it's stock configurations compared to the 350.

Personally it wouldn't matter to me if the truck had a 350 or a 400 in it. Both are good if they are treated properly.