440 ????

[SleeperScamp]

So why is a late 70's truck 440 rated at less than 300 hp. while the earlier car engine where 375+.... Is it all in the heads and compression ratio or what??? I just found one and was wondering how easy it was to wake them up ??? This will be mo first big block.... Thanks..

 

[wish4hemi]

The big differences are the cam and compression ratio. The heads on the later 440's are just as good as the early 440 heads as far as flow. Plus, the later 440 heads have hardened seats so you can run unleaded. It would be pretty easy to "wake up" a truck 440 with either some closed chamber heads or new pistons and a little more cam. The later 440's also have a cast crank, but unless you are planning on 600+ HP, that will not be a problem.

 

[Jim Lusk]

There are two completely unrelated factors. The first one is the way the horsepower was rated. Up through about 1971 the horsepower figure was GROSS HP. No accessories, etc. After that it was NET HP, with accessories. The 340 went from 275hp (a lie really as it was more like 320 according to the folks who worked in the dyno rooms) to 240hp (probably still a lie) in 1973 and only a small portion of that was related to the loss of compression and intake valve size. The rest was in the testing methods.

The rest of the hp "drop" was due to actual hp loss.