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Pulling the head of my 302 to replace stem seals. The head is sludgy and dirty so I'll give it a good cleaning. Thought I might as well give it hand valve lapping. Never done this before but looks like if I get the lapping tool and some lapping compound, it should be a simple procedure. What's the worse that could happen if I don't do it right. How can you tell if the seats and valves even need lapping.
 

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Not to dodge your question, but if the main task is to replace valve seals you do not need to remove the cylinder head
 

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I understand I don't have to remove the head to replace the seals, but there is a LOT of crud and sludge on the heads so I want to remove it to give it a good cleaning. I'm removing the intake anyway for cleaning so I figure I may as well take the heads off too.
 

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Pulling the head of my 302 to replace stem seals. The head is sludgy and dirty so I'll give it a good cleaning. Thought I might as well give it hand valve lapping. Never done this before but looks like if I get the lapping tool and some lapping compound, it should be a simple procedure. What's the worse that could happen if I don't do it right. How can you tell if the seats and valves even need lapping.
A clear sign is a carbon trail across the sealing edge of an exhaust valve or valve seat. You should make sure your old heads are within spec in terms of the clearance of your stems within the guides - if not get them replaced. You already mentioned new seals - thats good. Its a tough one to describe - in terms of a suitable technique for lapping. PM me and I will forward you a video. I can't do it here in my office - the damn firewall prevents it. Maybe I'm weird but I find lapping valves very satisfying - you are making a big improvement on your motors ability to seal. To pratice the technique you could do it on an old briggs and stratton flathead lawnmower motor - I did. Seems like a lifetime ago.
 

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Seems like a lifetime ago.
Wow you ain't kidding. I remember hand lapping when I was in H.S..(1979)
Did a valve job than hand lapped my 302. That was my first atempt at a rebuild and I have to admit it ran pretty darn good.I just send it out now.
good luck


mike
 

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Hand lapping can be a quick way to check the valve and seat visually.
When you lap there will be a dull gray band where contact occurs. This will reveal minor pitting or a barely bent valve.
 

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"When you lap there will be a dull gray band where contact occurs. This will reveal minor pitting or a barely bent valve."

"Well if your asking, the worst that can happen is that you don't get all the compound out of the chamber. Clean very well..."

+1 on both of the above statements.

When you are doing it, You can actually see what you are doing. You only need to do valve lapping if you are installing new valves. If you are keeping the old valves, It's not necessary unless you see extensive wear, or have to replace a damaged valve.

All I can say is take your time if you do it. Valve grinding kits and Valve grinding compound (Permatex recommended) can be bought at any good auto parts store.

You'll know you're doing it right when your wrists start killing you...lol... Just follow the above statements and you'll be fine.

You can also use a light wire wheel and clean all of the carbon on the inside of the chamber, then rinse out later. A light wire wheel on the end of a drill won't score the inside of the head...so don't worry about it..

Tony K.
 

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well if your asking, the worst that can happen is that you don't get all the compound out of the chamber. Clean very well...

M
A BIG +1.
Ironically, I have a set in my garage that I plan to lap in the the next day or so. It's freaky that I read this now. I literally just got off the phone with my brother before reading this thread. He's bringing me over his lapping paste tomorrow because I couldn't find my tin!
 

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Sorry to get off topic, but this thread sounds kinda sexual :makeout: :lol:
 
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