LS head flatness?
Thread Starter
Staging Lane
Joined: Oct 2024
Posts: 51
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LS head flatness? Hi guys, I have a forged 6.0 with 85mm turbo coming online next year. I had my short block machined and assembled by one shop. Months later, just had another shop hot tank and machine my heads 243 heads flat. I purchased a 24” straight edge with .001” flatness and some feeler gauges to measure the heads for flatness. In most areas I can’t get a .002” feeler under, however in one area particularly near one of the chambers I can get a .0025” feeler but not a .0028” feeler. Is this going to be a problem for boost?
Also… I purchased new valves and a BTR dual spring kit. I lapped my valve seats and new valves with valve grinding compound. My intake seats turned out amazing, however all exhaust valves have minor pitting on the inside chamfer(not outside chamfer) let me know if this will also be an issue.
Only two concerns I have trying to reuse old heads
Also… I purchased new valves and a BTR dual spring kit. I lapped my valve seats and new valves with valve grinding compound. My intake seats turned out amazing, however all exhaust valves have minor pitting on the inside chamfer(not outside chamfer) let me know if this will also be an issue.
Only two concerns I have trying to reuse old heads
.002 off is a bit much when you are paying for a set of flat surfaced heads. I would take them back. I don't think it'll cause any immediate issues, but if you are pushing the limit, its not the best way to start off.
Thread Starter
Staging Lane
Joined: Oct 2024
Posts: 51
Likes: 1
I read somewhere the tolerance is up to .004”? But with boost not sure maybe less. I do plan to run the Felpro gaskets I read they are very good at sealing even with looser tolerances
Thread Starter
Staging Lane
Joined: Oct 2024
Posts: 51
Likes: 1
Spray them with copper coat and torque them down a little bit more than spec. For that pitting I would pickup some lapping compound and lap the valves. Did you pay a shop for this work?? If so I'd find a different shop cause that one ain't doin for you
Its likely fine, but if you paid for the work and it was done incorrectly, why settle? At least bring them by and ask them to check the flatness in front of you. I paid to have a set milled by a shop and they later admitted they used a large belt sander to "surface" my heads. 
These days I just clean the surface w a razor at 90* and go. Its yet to bite me when using new 7 layer HG's. I don't suggest copper spray on new gaskets. Per GM install them dry. Running any sort of sealer in between stops/slows the heat transfer from the head to the block. I've used copper coat when reusing MLS gaskets on JY stuff to help seal the water ports. But thats all its good for IMO.
I agree with hand lapping in valves. I do it on all my budget JY builds. But again, if you paid for it...
These days I just clean the surface w a razor at 90* and go. Its yet to bite me when using new 7 layer HG's. I don't suggest copper spray on new gaskets. Per GM install them dry. Running any sort of sealer in between stops/slows the heat transfer from the head to the block. I've used copper coat when reusing MLS gaskets on JY stuff to help seal the water ports. But thats all its good for IMO.
I agree with hand lapping in valves. I do it on all my budget JY builds. But again, if you paid for it...
Last edited by Forcefed86; Dec 2, 2024 at 12:42 PM.
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Staging Lane
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this is after I lapped them with new valves
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Staging Lane
Joined: Oct 2024
Posts: 51
Likes: 1
Its likely fine, but if you paid for the work and it was done incorrectly, why settle? At least bring them by and ask them to check the flatness in front of you. I paid to have a set milled by a shop and they later admitted they used a large belt sander to "surface" my heads.
These days I just clean the surface w a razor at 90* and go. Its yet to bite me when using new 7 layer HG's. I don't suggest copper spray on new gaskets. Per GM install them dry. Running any sort of sealer in between stops/slows the heat transfer from the head to the block. I've used copper coat when reusing MLS gaskets on JY stuff to help seal the water ports. But thats all its good for IMO.
I agree with hand lapping in valves. I do it on all my budget JY builds. But again, if you paid for it...
These days I just clean the surface w a razor at 90* and go. Its yet to bite me when using new 7 layer HG's. I don't suggest copper spray on new gaskets. Per GM install them dry. Running any sort of sealer in between stops/slows the heat transfer from the head to the block. I've used copper coat when reusing MLS gaskets on JY stuff to help seal the water ports. But thats all its good for IMO.
I agree with hand lapping in valves. I do it on all my budget JY builds. But again, if you paid for it...
I had them milled flat and asked the shop if they checked flatness they said they don’t do that 🤣 so I had to buy my own stuff to check. Also I lapped all my valves and after noticed the pitting in the exhaust
Lol. Yea that's tells you everything you need to know about them
Find. Another. Shop.
I wouldn’t waste my gas driving back over there. Make a phone call and remind them that a bad rep on social media puts lazy businesses under. See if they remember suddenly that they do in fact check heads for flatness.
I wouldn’t waste my gas driving back over there. Make a phone call and remind them that a bad rep on social media puts lazy businesses under. See if they remember suddenly that they do in fact check heads for flatness.
Its likely fine, but if you paid for the work and it was done incorrectly, why settle? At least bring them by and ask them to check the flatness in front of you. I paid to have a set milled by a shop and they later admitted they used a large belt sander to "surface" my heads.
These days I just clean the surface w a razor at 90* and go. Its yet to bite me when using new 7 layer HG's. I don't suggest copper spray on new gaskets. Per GM install them dry. Running any sort of sealer in between stops/slows the heat transfer from the head to the block. I've used copper coat when reusing MLS gaskets on JY stuff to help seal the water ports. But thats all its good for IMO.
I agree with hand lapping in valves. I do it on all my budget JY builds. But again, if you paid for it...
These days I just clean the surface w a razor at 90* and go. Its yet to bite me when using new 7 layer HG's. I don't suggest copper spray on new gaskets. Per GM install them dry. Running any sort of sealer in between stops/slows the heat transfer from the head to the block. I've used copper coat when reusing MLS gaskets on JY stuff to help seal the water ports. But thats all its good for IMO.
I agree with hand lapping in valves. I do it on all my budget JY builds. But again, if you paid for it...
Good Christ, if they were brain surgeons, they'd probably use a chainsaw!!!