Looking for Opinions on these Valve Sealing Results

[VT_4G63]

Hi guys,

I’m looking for opinions on how to move forward with my build.

I have my engine completely disassembled for a refresh (timing, water pump, gaskets, seals, upgrades, etc.). I have the head apart and am up-grading lifters, cams, valve seals, springs, etc. etc.

I have cleaned the valve seats to a mirror finish using solvents and a nylon brush. I have run the stock valves on a brass wire wheel on my bench grinder (same way Jafro did it).

I have built a vacuum tester (again, same as Jafro did it).

I have NOT lapped the valves. When I run the vacuum test using the stock valves with the tool I built, the results are decent, but not acceptable to me. When I swap in a new set of BC valves the results become much better, but the vacuum held still falls eventually, albeit much slower than when the stock valves are used.

I’m going to post a video of my vacuum test results using the brand new BC valves (springs, retainers, keepers installed). Are these results acceptable? The vacuum rate falls pretty slowly and holds indefinitely at about 2 in/hg.

I’m assuming everyone is going to say lap the stock valves, but is that preferable to running the new BC valves with these results? I’m trying to avoid lapping the valves.Not because I can’t do it, I have all the tools required and know how to do it, I would just prefer to leave these valve seats virgin if possible.

If I didn’t have this new set of valves then obviously lapping would be the way to go, but are running the new valves with these results preferable to lapping the stockers?

Apologies for the long-winded post.

All opinions are welcome and valued.

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[BLACK'98DSM]

Why not quickly lap the valves? That removes minimal material but does create a better seal.

 

[VT_4G63]

Why not quickly lap the valves? That removes minimal material but does create a better seal.

Well, the reason I am reluctant to do so is I try to be as non-destructible as possible when attending to issues on these motors. I prefer to keep everything as virgin as possible. I realize that may be impossible at this point when this platform is so old. Mainly, I don't want to change the geometry of my valve train, even if it is a minuscule amount. Also, I am committed to completing all work on my cars in my garage, this head won't be going to a machine shop so I am concerned about being able to clean all the valve lapping compound out entirely.

However, I think I am going to do a quick lapping. If I can achieve a proper steady vacuum hold after having lapped the valves, it will be worth it.

 

[Drewpy Dawg]

Which is more important: keeping your valve seats factory virgin, or having valves that seal correctly?

 

[99dsmer4g63]

If the deck surface of the head is good sounds like I would lap the BC valves into the head then number them and clean the head out well after lapping. I like to use a siphon gun and lots of compressed air to clean out afterwards. Good luck

-Daniel