he may have low compression , a 340 with 8:1 is a dog & it has been rebuilt , a good cam like this can help build a lot of cylinder pressure & fool the engine into thinking it has more compression than it does & will wake it up . I did a 7.8:1 383 a few years back & we ported the heads & installed a Small engle cam & it became a whole different engine , if he is as low as 8:1 compression the K54 would be a better choice