[68 461 Bird]

Originally Posted by Fullsize455

My experience is that it is totally unnecessary. I've run numerous non-hardened seat engines for many miles on modern fuels with no additives, and have disassembled many more, and have seen no conslusive evidence that there is anything to worry about on a street engine. I think it may be more of an issue on race engines, maybe on higher compression engines or engines that are regularly driven hard, but on my street engines with lots of miles I haven't seen it be an issue. Again, my '71 455 with 241k, never used any additives, and all but one of my valve seats looked pretty decent still. The one exhaust seat that was bad was on a cylinder that was running a little low on compression due to tired rings, and that cylinder was burning a good bit of oil. I suspect that contributed to the exhaust seat pitting, as the others all looked good.

I've taken apart a bunch of virgin, untouched engines that showed no sign of excessive valve seat wear either, despite running tens of thousands of miles on modern fuels. I think it's much ado about nothing, to be honest. I've seen too many engines run too many miles and have too little wear to think there's anything to it.

I appreciate you sharing your experience on this as well. It seemed like I was wasting my money but no one was ever able to tell me they tore their engine down and saw anything from using it or not, especially with the amount of miles you have run. Thanks for the advice!!