in 1970, what was the difference between the 400 Turbo-Jet vs. Turbo-Fire? I know the Turbo-Fire was 265 hp, while the Turbo-Jet was actually a 402 cid big block with 330 hp, but don't know anything more than that.

 

Turbo Jet 400 was a sort of enlarged version of the 396 big block V8, the Turbo Fire 400 was a small block V8 which was more similar to the 350.

 

I found this. Monte Carlo: 1st gen 400 engine option clarification

this is from the article:
In 1970, if you ordered the SBC "400" (option code LF6), you received a
"265 hp Turbo-Fire 400 V-8 engine (regular fuel)". If you ordered the
BB 402 (option code LS3, and known as a "396" in any Chevy SS except for
the Montes), you received a "330 hp Turbo-Jet 400 V-8 engine".

 

bingo^^^ 400 is the small block. 402 is the bored out 396 big block. the big blocks are physically larger, and have a canted valve setup. the stroke of the 400 and the 402 are very similar this gives the 400 big block like torque. its also the reason why the 400s crank is used in 350s to stroke them to 383. i personally have a 400 small block and can tell you they make a ton of torque, dont generally like to rev (they dont need to to make power), and are known for running hot. i wouldnt pick the 402 over the 400 unless the car i was going to put it in came with a big block. bbc parts are expensive, theyre heavy, and they dont just slide into a gbody.

 

thanks guys, that tells me exactly what I need to know. If a small block 400 was replaced with a big block, would the springs need to be changed for the additional weight?