Valve job
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,174
Likes: 259
From: Virginia
Valve job
Can someone give me some info on what all is usually involved with a valve job? The reason I ask is because I had a shop pull my motor and send it off to a machine shop to be freshened up. Everything was fine with it except they ended up doing a valve job. From what I understand the seating area of the valve was too wide, or at least I think…. Has anyone ever heard of a bone stock low mileage LS3 having issues that would require a valve job? If so what could cause it? I had some excessive ticking that I could isolate to certain cylinders so I’m thinking it was because of this. Everything I’ve read basically says these motors are solid as hell, So I’m not sure what caused the issue but what exactly does a valve job usually involve?
Safety Car
Joined: Sep 2005
Posts: 4,222
Likes: 643
From: Orange County Ca
"I had a shop pull my motor and send it off to a machine shop to be freshened up"
OK, why? What was the problem?
Did they only do a valve job?
Usually, when you send a whole engine out, it would be to get a major overhaul.
Yes, valves do wear over time, but it's not unusual for modern engines to go 200+k miles without needing valve work. But, on a engine getting a complete rebuild, it is common to do a valve job even if not totally needed. It is cost effective over the long run.
OK, why? What was the problem?
Did they only do a valve job?
Usually, when you send a whole engine out, it would be to get a major overhaul.
Yes, valves do wear over time, but it's not unusual for modern engines to go 200+k miles without needing valve work. But, on a engine getting a complete rebuild, it is common to do a valve job even if not totally needed. It is cost effective over the long run.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,174
Likes: 259
From: Virginia
"I had a shop pull my motor and send it off to a machine shop to be freshened up"
OK, why? What was the problem?
Did they only do a valve job?
Usually, when you send a whole engine out, it would be to get a major overhaul.
Yes, valves do wear over time, but it's not unusual for modern engines to go 200+k miles without needing valve work. But, on a engine getting a complete rebuild, it is common to do a valve job even if not totally needed. It is cost effective over the long run.
OK, why? What was the problem?
Did they only do a valve job?
Usually, when you send a whole engine out, it would be to get a major overhaul.
Yes, valves do wear over time, but it's not unusual for modern engines to go 200+k miles without needing valve work. But, on a engine getting a complete rebuild, it is common to do a valve job even if not totally needed. It is cost effective over the long run.
Le Mans Master
Joined: Dec 2005
Posts: 6,999
Likes: 1,685
From: Southeast TX
If I pull a set of heads for whatever reason and they have more than a few miles, I'm going to do a clean up mill to get the surfaces perfectly flat. To do that, you need to disassemble the heads for cleanup. At that point, it's just not that much more money to do a valve job. What you get back is essentially a new set of heads to bolt back on. Good opportunity to upgrade the valve springs as well. It doesn't cost any more ( labor wise) to assemble the heads with new valve springs and seals vs using your old chit.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,174
Likes: 259
From: Virginia
If I pull a set of heads for whatever reason and they have more than a few miles, I'm going to do a clean up mill to get the surfaces perfectly flat. To do that, you need to disassemble the heads for cleanup. At that point, it's just not that much more money to do a valve job. What you get back is essentially a new set of heads to bolt back on. Good opportunity to upgrade the valve springs as well. It doesn't cost any more ( labor wise) to assemble the heads with new valve springs and seals vs using your old chit.
Instructor
Joined: Nov 2022
Posts: 191
Likes: 142
From: Thornton, Colorado
A few things
The valve guides wear and can allow the valve to wobble a bit. This can wear the valve seats.
A 3 angle valve job has the seat ground at 45 degrees with a 30 degree ground at the edge. The valve itself is ground at 44 degrees which gives a very thin contact area to help seal the valve. This can wear down and the interference of the 44 and 45 can flatten out a bit and widen the sealing point. This can cause leaking of compression failure and in some cases the hot gases will start to burn a channel in either the valve or seat or both. This is what is called a burned valve. Things may have changed a bit since I did valve jobs in the late 80's but sure the basics are the same.
The valve guides wear and can allow the valve to wobble a bit. This can wear the valve seats.
A 3 angle valve job has the seat ground at 45 degrees with a 30 degree ground at the edge. The valve itself is ground at 44 degrees which gives a very thin contact area to help seal the valve. This can wear down and the interference of the 44 and 45 can flatten out a bit and widen the sealing point. This can cause leaking of compression failure and in some cases the hot gases will start to burn a channel in either the valve or seat or both. This is what is called a burned valve. Things may have changed a bit since I did valve jobs in the late 80's but sure the basics are the same.
Thread Starter
Melting Slicks
Joined: Nov 2011
Posts: 3,174
Likes: 259
From: Virginia
A few things
The valve guides wear and can allow the valve to wobble a bit. This can wear the valve seats.
A 3 angle valve job has the seat ground at 45 degrees with a 30 degree ground at the edge. The valve itself is ground at 44 degrees which gives a very thin contact area to help seal the valve. This can wear down and the interference of the 44 and 45 can flatten out a bit and widen the sealing point. This can cause leaking of compression failure and in some cases the hot gases will start to burn a channel in either the valve or seat or both. This is what is called a burned valve. Things may have changed a bit since I did valve jobs in the late 80's but sure the basics are the same.
The valve guides wear and can allow the valve to wobble a bit. This can wear the valve seats.
A 3 angle valve job has the seat ground at 45 degrees with a 30 degree ground at the edge. The valve itself is ground at 44 degrees which gives a very thin contact area to help seal the valve. This can wear down and the interference of the 44 and 45 can flatten out a bit and widen the sealing point. This can cause leaking of compression failure and in some cases the hot gases will start to burn a channel in either the valve or seat or both. This is what is called a burned valve. Things may have changed a bit since I did valve jobs in the late 80's but sure the basics are the same.
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Instructor
Joined: Nov 2022
Posts: 191
Likes: 142
From: Thornton, Colorado
Again, it's been a long time....
Old days small block Chevy you would have to ream the old guides out and press in new guides. New stuff is probably guide inserts already so just drive out the old and in with the new. Then run a reamer to ensure proper diameter. Also knurling the guides give a path for better oiling and they tend to last longer. Back then bronze guides were the way to go but I'm sure they have better materials these days.
Old days small block Chevy you would have to ream the old guides out and press in new guides. New stuff is probably guide inserts already so just drive out the old and in with the new. Then run a reamer to ensure proper diameter. Also knurling the guides give a path for better oiling and they tend to last longer. Back then bronze guides were the way to go but I'm sure they have better materials these days.