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I bought a 235 that the previous owned salvaged out of a truck he bought for parts. Compression is very good at 145 to 155. If fires up and idles nice with decent oil pressure.
But rev it up and it smokes pretty bad, like hope the neighbors don't call the fire department. With fresh plugs it blacken'd all 6 fairly quickly. I tried running it for about 3/4 hr with sea foam in the oil, gas, and down the carb. No improvement. There was oil dripping from the exhaust, but that could be from all the sea foam down the carb.
Running 10-30 oil. It has hydraulic lifters, block number says a 58-62. Any ideas? I'm putting the motor in a 29 Olds coupe which is a big enough project, I was hoping to not have to tear the motor down right now. Any ideas ? I'm supprised with the compression being that good that it push that much oil past the rings.

If it is a 59-62 235 it NEEDS the rockers that are for a higher pressure rocker system. If it has the rocker for a low pressure engine it will put too much oil on the valve train. I had that problem when I rebuilt my 59 235. I was smoking at stop lights and had oil in my exhaust pipes. Once it put the proper rocker on it, it does not smoke or have oil in my exhaust. The low pressure rockers have the groove in line with the hole in the top of the rocker, the high pressure rockers the groove is offset to the top hole. Basically I was flooding my top end and pulling oil around my valve seals.

Try cleaning out the draft tube .

The valve guides may very well be worn to the point of allowing oil to essentially drain down the valve stem. The seals for these motors consist of a small single rubber ring on the valve just below the keeper groove. They last about 4 hours. Kidding of course but I have never taken a 235 or 261 apart that had those seals intact in 40 plus years. So if you are sure you are running the correct rockers for the motor, try replacing the valve stem seals. If that does not do it, then a freshening up of the valve head may be in order.

Also if it has not been used the oil rings may be gummed up and I have read on here about a mixture to clean the inside of the motor that may help free up the gummed up inners .I think it was from Hotrod Lincoin

Here is pic, are these the correct rockers ? I don't understand how these motors get oil to the valve. Oil comes out the hole in top of the rocker and flows accross the top back to the push rod, but not towards the valve. Exspecialy on the intake rocker which slopes upward. Assuming the oil gets to the top of the valve in some way, the valve seal is an o-ring just under the keeper, which would stop oil from going down the stem ? So how does the valve stem in the guide get lubricated. Hopefully not dumb questions.

There's a lot more oil flow from the spit holes at driving speed. It will barely ooze out at idle. You won't be able to see the lube groove orientation in the rocker arms without disassembling the rocker and shaft and looking inside the rocker pivot holes. If the groove is offset from the spit hole, you have the late model rockers.
Jerry

There is a possibility that you can identify your rockers without removing them. There are numbers cast into the side of each rocker. They’re difficult to read, but if you can post one or more of these numbers our parts experts may be able to identify which engine they came from.

I added a picture of the numbers.

Why is the overflow tube pinched off? Won't that significantly increase the oil supply to the rockers and result in increased oil consumption through the guides?

My blog post shows a lot of information about rockers and the oil supply.
https://chev235guy.blogspot.com/search/label/235%20Rocker%20Oiling?m=0