bennynolt_2

Hey yall, I have a ‘96 f150 with the 351W, recently I rebuilt the top end and while I had everything apart the bottom end looked fantastic for 275k miles. After the rebuild o switched to 10w30 oil instead of the recommended 5w20 or 30, whatever they wanted. Anyway, I noticed that I’m burning oil now, would that changing oil weight cause it? Could it have been something I did when I rebuilt it? Need some advice here thanks

raski

I doubt the issue is from the oil which you used,

Make sure the PCV system is working properly. Couldn't tell exactly from your description if only the top end was rebuilt but I have heard that a fresh top end rebuild over an old lower end, has sometimes resulted in oil being drawn past worn, old rings.

If the entire engine was rebuilt, look for poor or incomplete seating of the rings

manicmechanic007

Agreed,
I would however, pull the valve covers back off and make sure your valve stem seals have not walked up the valves
Meaning, check if the seals are stuck down on the guide like they are supposed to be
The rings, if now stuck, might be freed up with some trans fluid in the oil for a change or two
How much oil is it burning in 1000 miles?

bennynolt_2

I will definitely check the valve seals, that makes sense. But I haven’t yet gone 1000 miles since I’ve noticed the blue smoke, but I’ll be checking regularly, I don’t think it’s anything crazy but enough to be annoying.

raski

Before I would start doing any disassembly, a compression check will serve dual purposes.