I know this is a Monte Carlo forum but I need a little bit of help with my Ford truck. The guys on the ford-trucks forums are no help and are rude so Im done with that forum. I have a 1990 Ford F250 with a 351w and I have some blow-by. I have smoke coming out of the valve covers which is saturating the air box filter box with oil. It first started off just doing that under load, but now its smoking at idle. As soon as I crank it smoke comes out even on a cold start. I was wondering how can I tell if its the valve seals or the piston rings that need to be replaced? I started a compression test and did 4 cylinders and lost the paper lol. From what I can remember I know some of them have atleast a 10-15 psi difference. I know it would be easier to just swap in another motor but I know that this one is good, it is a fresh rebuild from the previous owners, atleast thats what they told me lol.

 

Check the PCV check valve and replace it. Sounds like it's malfunctioning.

 

Thanks for the fast reply, but I failed to add that I already changed the pcv with 3 new ones to make sure none were faulty but the same thing. I would also like to add that the smoke is white.

 

Well if that's the case then it sounds like a blown head gasket. White smoke generally denotes a coolant burn. If the exhaust smells sweet I can bet 10 to 1 that's what your problem is.

 

Cool! I cant tell if I smell coolant because the truck has no cats and the exhaust stops right under where the passenger seat is. I might get brave and try to tackle that gasket myself. You know now that you mention it when I first brought the truck it wasnt smoking at idle only when driving then I removed the intake manifold attempting to do a self-fix, and said forget it and I put it back on. After I put it back together it started to smoke at idle also. Dunno if that has anything to do with it...

 

When you put the intake manifold back on did you clean the mating surfaces, use new gaskets and sequentially torque the bolts? If not you could have water seaping into the intake runners. That would be the first thing I'd suspect. Then I would run a compression test. If you find two adjacent cylinders with low compression chances are you have a blown head gasket. If the test comes out okay run a wet compression test. Pour about a tablespoon of oil into a cylinder then check compression. Do this to all cylinders. If the compression stays within a couple pounds of the dry test the rings in that cylinder are good. If you see a significant increase in compression you have a problem with the compression ring. It could be stuck, cracked/broken, wasn't installed properly or too large of an end gap. At any rate the engine will need disassembly and inspection to determine the exact cause.

 

I did clean the surfaces and I did re-use the gaskets (lol) I didnt think it would be a problem because it looked good. I guess ill man up and re-do the compession test whenever my neighbor buys a new battery and returns mine lol. With the wet compression test, does it have to be new oil? I have the oil from the previous oil change in my little green recyclable bucket thingy... You guys are great!

 

You should have a minimum of 150 lbs compression on each cylinder. You should also do a cylinder leak down test. This is when you charge each cylinder with compressed air with all the intake and exhaust valves closed. If you hear air escape at the tail pipe you have bad exhaust valves, at the intake, then bad intake valves, and at the oil dip stick tube then it is bad rings.
It sounds from your description that you have bad rings. With bad rings your blowby get worse as the engine warms.

 

Did you use any rtv or just slap the old gaskets on?

I would say do a compression check and a wet one as advised above

But I would definitely replace the old gaskets with new ones also check your oil and see if there is any water in it

 

sound like blow by think you need new valve seals head need to be done new valve seals