Burnt valves

My son and myself rebuilt a 1986 Chev. crew cab pickup in 1998. We basically rebuilt everything except the engine. It has a 350 and has unknown miles on it. I have $6 thousand in this truck and don’t want to put any more money in it as it is worth maybe 500.00 now with the price of gas. So the question is how can I un stick the intake and exhaust valves on # 7 cyl. I have pulled the valve cover and found both valves stuck open. The rocker arm was off one of the valves and I am guessing that carbon is the cause of them not fully closing. I could pull the head but I am wondering if there is some way to clean the carbon without removing the head. I was advised that the lower end is too worn for a new valve job and as I don’t drive this truck much and I have so much money in it my only option is to keep it. I just need to get these two valves to close. Any ideas.

Spray WD-40 or a similar product on the valve stem and tap the valves repeatedly to see if they will release. If they refuse to release they are likely bent. If they release inspect the push-rods and rockers and replace if necesssary. With the valves seated, presurize the cylinder and check for excess pressure loss (possible broken piston, etc.).

If you turn the engine by hand do the valves still move up and down?

If it is indeed carbon build up, running some Seafoam through the intake MIGHT clear it up. But as your topic suggests, if this has been like this for a while, the exhaust valve is probably going be scorched and even if it’s cleaned off, it still won’t seal. To fix it properly, you will need to remove the head, but since the bottom end is junk too, I wouldn’t bother. You you can probably pick up a used 350 for a couple hundred bucks, tops, and since it sounds like you’re pretty mechanically handy, swapping it out yourself shouldn’t be too much of an ordeal.

Also, depending on how the body is, I would dispute the 500 valuation. Older crew-cab pickups usually hold their value surprisingly well because they didn’t make very many and there’s people who really like the simplicity of older trucks but need the extra passenger space.

One good thing is that you can totally screw around with the engine and it won’t hurt a bit. Get the heads off and remove the valves. (or this) The valve spring are now extremely weak and every one of them has to go. If you can pry the valves up, you can change the springs. If you have an air compressor, it will keep the valve up while you do it. Some mechanics have fed rope into the cylinder instead of air for this. Spring compressors are cheap enough. You will need 16 new rocker nuts too. Don’t be afraid to mess around, you have nothing to lose. If you have a burned valve, it probably won’t bother you too much anyway.