(Another) lapping valves question...
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Teching In
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From: State Capitol Raceway, LA
(Another) lapping valves question... I have a set of supposedly low mile (2x,xxx IIRC) Z06 243s. I verified that the valves are hollow and the heads "look" like they could be low mileage. I'm installing the Comp trunnion upgrade and an all-inclusive dual valve spring kit. I dug around on the 'net for a while and I'm still not sure one way or the other if I should give these heads a simple lapping. I found plenty of debates on lapping after a full-on valve job, but that's not what I'm doing. I recall reading that, in stock form and fresh out the factory, the valves don't seal to the heads as good as they could. I'm just talking about giving them a few rubs with the finest grit I can find and checking them with Prussian Blue or something like that.
If it matters, these are going on an LQ9 with a 226/230, .598/.600, 113LSA, 111ICL, +2
If it matters, these are going on an LQ9 with a 226/230, .598/.600, 113LSA, 111ICL, +2
Joined: Aug 2007
Posts: 24,241
Likes: 89
From: Turnin' Wrenches Infractions: 005
I run fine grit on all my heads before I install them. 1. it gives a fresh true sealing surface, and 2. if something is amiss, you'll notice it before your engine is together. I've found from my limited experience that when a valve runs true, the sealing surface is clearly visible in the compound around the perimeter. I don't see why this would require any prussian blue.
I don't recall the name of the place, but there is a kart parts place in Virginia near Williamsburg that specializes in Briggs & Stratton cart motor w ork. They have a lot of different grits of lapping compound with a lot of nice tools to do the work. I got my compounds from them when I lapped my stock heads and my Dart heads.
Just make sure you clean the heads really well afterwards so there is no grit left.
Just make sure you clean the heads really well afterwards so there is no grit left.
I would get a valve job done if you have the heads off the motor for a few reasons. You will pick up flow with the valve job and the heads should seal no problem if you have someone reputable do a quality 3 angle valve job for you. If your knowledgeable with cylinder heads I would then blend the valve job in and do some bowl work. You can pick up 30CFM on a head and lose no velocity.
