Acceptable Valve Pitting
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Cross-Country
Joined: Dec 2023
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Acceptable Valve Pitting
G'day all. After some advice. I bought used E7 heads to replace the E6 heads on my 1990 351. This is an intake valve from the used heads. My question is, if lapping cleans up the sealing surface okay, would these be okay to use? Keeping in mind this is a stock, low budget exercise.
Cargo Master
Joined: Oct 2020
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Lapping doesn't have much to do with a proper valve job it is used mostly just to check width and position of the seat on the face of the valve.
Cargo Master
Joined: Oct 2020
Posts: 2,657
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Cargo Master
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The way I see it is it's too big of a job to do it half as*. You will be really upset when you have to do it over again because you were too cheap to do it right. I think many of us have been there/done that before.
Both surfaces need to be machined. I tend to lap the valves after machining just so I can see how well the seating surfaces are. I've seen good looking machined surfaces not seal. It does not hurt after all the work is done, is to tip the heads over and pour a light liquid to see if they leak past the valves/seats. When it comes to exhaust valves on higher mileage engines, they get replaced. I've seen exhaust valves not last a second lifetime and will not go down that road again.
I have never had a comeback when I know for a fact the valves are sealing on the bend. Knowing they are sealing is better than thinking they are going to seal.
Both surfaces need to be machined. I tend to lap the valves after machining just so I can see how well the seating surfaces are. I've seen good looking machined surfaces not seal. It does not hurt after all the work is done, is to tip the heads over and pour a light liquid to see if they leak past the valves/seats. When it comes to exhaust valves on higher mileage engines, they get replaced. I've seen exhaust valves not last a second lifetime and will not go down that road again.
I have never had a comeback when I know for a fact the valves are sealing on the bend. Knowing they are sealing is better than thinking they are going to seal.
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Tuned
Joined: Sep 2014
Posts: 469
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That seat looks rough.
most guys will buy a set of aftermarket aluminum heads for around the same money as having oem castings reworked.
I like and want factory cast iron heads and was wiĺing to pay for what I wanted. I have my reasons.
I could have spent the same money and had aftermarket aluminum.
The hot ticket is to make a peice of clear plastic with a hole for a fitting and apply vacuum to the hole.
This will check valve sealing and as you play with it use can see which ports required less vacuum pumping in order to pull aa vacuum. Depending on your setup you can see how long it holds a vacuum.
by time you find a machine shop and start pricing rebuilding those heads and wait for them to do them..oh and how are the valve guides? Doing a valve grind with marginal guides won't last as long.
sorry but I think the most affordable route is aftermarket, it wasn't always this way.
most guys will buy a set of aftermarket aluminum heads for around the same money as having oem castings reworked.
I like and want factory cast iron heads and was wiĺing to pay for what I wanted. I have my reasons.
I could have spent the same money and had aftermarket aluminum.
The hot ticket is to make a peice of clear plastic with a hole for a fitting and apply vacuum to the hole.
This will check valve sealing and as you play with it use can see which ports required less vacuum pumping in order to pull aa vacuum. Depending on your setup you can see how long it holds a vacuum.
by time you find a machine shop and start pricing rebuilding those heads and wait for them to do them..oh and how are the valve guides? Doing a valve grind with marginal guides won't last as long.
sorry but I think the most affordable route is aftermarket, it wasn't always this way.
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