Cantedvalve 128 Report post Posted May 20, 2019 Bit of history here. Back some 20 years ago, I bought a set of rebuilt heads from eBay. They cam assembled, and everything looked really good. I bolted them to my engine, and thought nothing of it. Since then I have probably 15-16k miles on these heads. No issues. These are 1971 351-2V heads (not my originals obviously). Fast forward to today. I am rebuilding these heads with all new components - new single piece stainless valves with single groove locks, new retainers, and new springs. I have taken these heads apart to find a) the guides have been replaced, and they are in great shape, and b) the valve seats all look great. I have checked the install height for the springs, and I am finding that all the install heights are at 1.795-1.800", exactly where I want them, and very consistent, meaning (hopefully) that all seats were ground to the same depth. My plan was to blue the valves, and if minor lapping was needed, lap them in, and leave it at that. Now, @1969_Mach1 has asked me why I dont have the heads machined and the valves lightly ground to ensure a quality seal. My response is, because as far as I can see, they don't need it. My position is that if the blue and lapping proves to show a good seal, that I dont need to worry about machining the seats, that the valves will seal just fine. Since the guides are nice and tight, and all the valves were in like new condition (save some carbon build up), nothing points me towards thinking I need to do any machine work. But I kick the question to a larger audience... in this scenario, is lapping the valves in a good option? This is a street machine with under 5000 miles annually. No racing, just spirited stupid driving. Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted May 20, 2019 Lapping them will tell you if everything is correct or not with the seats and valve face. I always lap them but you do not need to blue them and this can actually inerfere with the lapping process. Also, not all cylinder head machinists do the same level of quality, therefore, it is entirely possible that if you have them redone, they might not be as good as the are now, and if this occurs, you would have paid to have a lesser quality job done on them. 1 Cantedvalve reacted to this Quote Share this post Link to post Share on other sites
DocWok 30 Report post Posted May 20, 2019 If you correctly blue the valves i.e. apply it correctly, very thin - tap the valve up and down a couple of times without rotating it and it shows a correct seat, then lapping the valves will achieve nothing extra. 2 1969_Mach1 and Cantedvalve reacted to this Quote Share this post Link to post Share on other sites
Cantedvalve 128 Report post Posted May 21, 2019 Yeah I figured that out. So as both find the same thing, I think I will blue them and avoid the lapping compound unless I absolutely need to touch up things Quote Share this post Link to post Share on other sites
barnett468 418 Report post Posted May 21, 2019 1 hour ago, Cantedvalve said: Yeah I figured that out. So as both find the same thing, I think I will blue them and avoid the lapping compound unless I absolutely need to touch up things That's a good plan to start with. I used graphite spray for this purpose when I ran the cylinder shop for an engine machining company. 1 Cantedvalve reacted to this Quote Share this post Link to post Share on other sites
