Valve Lapping
Thread Starter
Senior Member
Joined: 01-16-2017
Posts: 384
From: Ohio
Valve Lapping
I have my 2.0 LNF cylinder head apart to replace the valve seals. I'm not planning to grind the valves since I'm also not planning to replace pistons, liners, and rings (I.e., I don't want to freshen up the top-end, to then create excessive blow-by on the bottom end). But I was thinking of lapping the valves at least. I've done this on plenty of other engines in the past, but is there any reason I should not do this on the LNF? In other words, is there any weird nuance about the engine/head that prohibits or discourages valve lapping?
Thanks in advance
M Ridzon
Thanks in advance
M Ridzon
Moderator
Joined: 01-23-2009
Posts: 26,543
From: Fredericksburg,VA
The shop manual goes into using Prussian Blue, but doesn't go into fixing a problem.
It goes into replacing guides and springs, but not valves.
My understanding is there is not much extra metal on the heads for any real machining, I don't think lapping would hurt, grinding no.
It goes into replacing guides and springs, but not valves.
My understanding is there is not much extra metal on the heads for any real machining, I don't think lapping would hurt, grinding no.
Platinum Member
Joined: 12-06-2009
Posts: 11,721
From: Alabama
My opinion.
Lapping the valves is to achieve a better seal, which should create better cylinder pressure. A better seal is just going to make that pressure exert on the rings.
If you're not going to replace the rings, you "may" create more blow by if the ring condition is marginal.
Lapping the valves is to achieve a better seal, which should create better cylinder pressure. A better seal is just going to make that pressure exert on the rings.
If you're not going to replace the rings, you "may" create more blow by if the ring condition is marginal.
Thread Starter
Senior Member
Joined: 01-16-2017
Posts: 384
From: Ohio
My opinion.
Lapping the valves is to achieve a better seal, which should create better cylinder pressure. A better seal is just going to make that pressure exert on the rings.
If you're not going to replace the rings, you "may" create more blow by if the ring condition is marginal.
Lapping the valves is to achieve a better seal, which should create better cylinder pressure. A better seal is just going to make that pressure exert on the rings.
If you're not going to replace the rings, you "may" create more blow by if the ring condition is marginal.
Senior Member
Joined: 08-03-2010
Posts: 3,564
From: Lake Ronkonkoma, N.Y.
Is the head off ? Guess it is. Level the head and fill the chambers with washer fluid and measure how fast it leaks, draining the combustion chamber, past the valve seats. Lap the valves and do it a second time. Tell us what you for found. Lapping the valves isn't going to raise the compression ratio that much, if any. Unless those valve seats and valves were toast to begin with.
Last edited by Cat Man HHR; Jan 28, 2019 at 03:46 AM.
