Quoted From OnThe7ThDayFord:
Yes sir Im from Oklahoma. Next time ill make sure i come here and ask first…
I had heard a few times before that increasing weight can help but never did it Until now – A few guys at autozone talked me into it.
Lessoned learned
Its very sad how people are so misinformed regarding oil viscosity as well as what those numbers exactly mean on the bottle.
Increasing the viscosity of oil to try to take up the ‘slack’ from mechanical wear is never a good idea. You usually make it worse by starving the engine of oil.
The only time i would use 20w50 is if i participated in demolition derby’s and knew my cooling system would be ineffective after a few front end hits.
I am really not sure how well mixing a conventional oil and a synthetic would be due to the different chemicals. I would do a drain and refil.
Going back to the 351, you will have to do your research. I know the 351w is about 1 inch taller than the standard 302. I also believe the bell housing bolt patters are the same. A lot of the internals are interchangeable too.
If you decide to stick with EFI, i have no idea what changes you will need to make, if any for the PCM.
Usually most people if they decide to use a different engine will go Carb or use an aftermarket engine management system like Megasquirt for example.
If you go with this 351, you will be spending ALOT more money trying to get it running over buying a used lower mileage replacement long block or even short block for your F150.