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By 58F600 - 5 days ago
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So we finally got to put a little time under the hood and do some long overdue maintenance.
I did hook up the oil pressure idiot light and it kinda works 😂. We do have some oil pressure!
I adjusted the valves and found all the exhuast valve had lost all their lash. We don't know much about this engine, but from having the pan off, the timing chain is super tight. It's nice and clean. Mains have a little wear. It has two visually different rockers on one side vs the other. And one rod that looks different than the rest. I'm guessing a rural Napa rebuild 30 years ago and then not much use around the farm until we strapped a turbo on it and went cross country.
The heads are 62 variants. I forget exactly.
For those running boost, is this normal for the first 10k miles? Or do the seats erode? Valve stretch? We really didn't turn it past 3800rpm, but it does pull long hills at 17k lbs, and 12psi.
Just wondering what I'm in for. I've always been a little concerned about the exhuast valves. I'm sure they are stock or super cheap stock replacements. Our Turbo inlet EGTS are routinely 1500° plus. Plugs look great.
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By Joe-JDC - 5 days ago
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Sounds like the valve seats are going away with heat and boost. 12psi is a lot for the street and extended time, even with lower compression. JMO, others may differ. I have seen valves tulip from heat and the seats go away without boost but pulling a lot of weight on long trips in a rebuilt engine. Joe-JDC
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By KULTULZ - 4 days ago
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"I adjusted the valves and found all the exhuast valve had lost all their lash. We don't know much about this engine, but from having the pan off, the timing chain is super tight. It's nice and clean. Mains have a little wear. It has two visually different rockers on one side vs the other. And one rod that looks different than the rest. I'm guessing a rural Napa rebuild 30 years ago and then not much use around the farm until we strapped a turbo on it and went cross country.
The heads are 62 variants. I forget exactly."
What was the engine/cyl heads (272-292) taken out of, PASS CAR, LT or MT. If MT the exhaust valves may be sodium filled and usually require lash caps. What shape is the rocker arms contact faces in?
If valve seat recession, I would think it would need hardened exhaust seats if using ethanol laced gasoline.
Are you using a pyrometer? What is the truck's GROSS VEHICLE WEIGHT RATING and how heavy loads and slow pulling speed do you haul?
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By Big Tim - 4 days ago
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Thats alot of EGT for what are probably stock valves. Probably gonna need to pull the heads and see what they look like.
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By Litshoot - 4 days ago
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12 psi in a turbo isnt very high, especially if your running all stock. 1500 egts seems a little hot especially unknown valves and seats was that hauling up hill or steady cruise. Hardened seats and stainless valves good springs would be nice insurance. Alternatively you could adjust the valves again and check much more often. Maybe the shade tree build 30 years ago didnt lap the valves and they all just setting together. What did you set the lash to originally.
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By 55blacktie - 4 days ago
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Litshoot (11/2/2026)
12 psi in a turbo isnt very high, especially if your running all stock. 1500 egts seems a little hot especially unknown valves and seats was that hauling up hill or steady cruise. Hardened seats and stainless valves good springs would be nice insurance. Alternatively you could adjust the valves again and check much more often. Maybe the shade tree build 30 years ago didnt lap the valves and they all just setting together. What did you set the lash to originally.
For comparison purposes, the 1957 F-Code was 5 psi. I agree with Joe. Anything is possible, but it depends on how it's built (parts), how you intend to use it, and how long you want it to last.
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