| oatycorb | -- 11-16-2020 @ 3:16 PM |
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I'm in the midst of reassembling my 59ab engine. I have brand new stainless steel valves and freshly cut 3 angle valve seats. The gentleman who cut the seats recommended that I install the valves without lapping them, which seemed out of the norm to me. When I asked why he said that it's not necessary to lap the valves if the valves are new and the seats are newly cut. I've built quite a few different car and motorcycle engines over the years but I have to admit I've never heard this before. Today I checked the valve to seat contact by coloring the face of each valve with a sharpie where it contacts the seat and rotating it back and forth. There was a nice thin uniform ring around each valve where it seats, right where it's supposed to be. So, to lap or not to lap, that is the question!
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| kubes40 | -- 11-16-2020 @ 4:31 PM |
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In my humble opinion if they all check for fit as well as the one you'd tested, I'd not lap them. I would check each and every one. Mike "Kube" Kubarth
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| oatycorb | -- 11-17-2020 @ 3:02 PM |
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Thanks Mike, I checked a few more valves today and they all look pretty good, I'll check the rest tomorrow. The guy who cut the seats spent a lot of time getting each seat nearly perfect and it shows. I always thought lapping valves was just par for the course when you're building an engine. Learn something new every day. Thanks for your advice.
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| 37RAGTOPMAN | -- 11-24-2020 @ 11:23 AM |
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hi oatycorb if you want to check the valves, you do not have to lap the valves, but can use bluedykem on the seat and rotate the valve and this will tell you were the valve rides, it should be in the center or close to it, this is by some of it rubbing off hope this helps, 37Ragtopman
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| oatycorb | -- 11-24-2020 @ 3:50 PM |
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Hi Ragtop guy, I actually did get some machinists blue dye to check all the valves, and to my surprise a good number of them evidently weren't sealing completely. I marked the valve and just turned it back and forth a little in the seat, maybe a third of a turn back and forth. There were a number of valves that weren't sealing all the way around where the blue wasn't even touched in some places. The guy who ground the seats was using a 1950's vintage Black and Decker valve seat grinder in pretty good shape but in retrospect it probably isn't state of the art anymore. I did a very light lapping of each valve and all the seats cleaned up with minimal effort, with the lapping ring being more or less in the center of the valve contact face. A good number of them were perfectly in the middle, the rest of them being far enough away from either edge that I tend to think they'll be fine in a bone stock 59ab engine. Thanks for the advice!
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| agriffey | -- 11-24-2020 @ 9:33 PM |
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In the late sixties I worked next to an old Englishman that taught me to stop lapping the valves! He just slapped them closed a few times before he put the springs and keepers on. We did a test to prove the results. We lapped some of the valse and left some not lapped. A leak down test showed better on the ones we didn’t lap. He said the lapping compound leaves ting grooves in the seats and valves. The lapping compound is hard to wash out too.
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| oatycorb | -- 11-25-2020 @ 4:10 PM |
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That's interesting agriffey. I've heard similar stories before. Unfortunately in my case, there were a number of valves whose seats wouldn't have cleaned up by simply snapping the valves shut. I just did a VERY light lapping of each valve, for maybe 10 or 15 seconds apiece, and they all came out looking pretty good, so I'm considering the job finished. Thanks for the info!
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