achieving .035-.040 quench is critical for being to run a higher CR on any given octane of gas & this is hard to accomplish with open chambered heads such as the 452's. Quench or no quench may mean the difference in being able to run as much as 1 full point of CR higher on the same fuel. more squeeze is more power. My suggestion if you have not made a purchase yet would be to get a set of stealth alum heads & they are on sale for $899. just have your competent machine shop check the valve job/guide clearance & locks/retainers on them. If you dont have quench you are for sure leaving power on the table that could be had.