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I bought a 74 f100 this year. I'm wondering if the engine is original. When I bought spark plugs I was given the 5/8 plugs, but I removed 13/16 plugs. The store said the computer called for the skinny plugs. The engine has Mercury valve covers (I know they could have been changed). Today I was replacing the coil (which had Ford part numbers on it) and I cleaned up the metal tag that was on the bolt that held the coil to the intake. Anybody know whether this is the stock 360 or is it a 66 Mercury 390? This is the tag.
If your tag is for that engine it would be a 66 390. measuring the stroke is the only way to know for sure since heads and everything else are interchangeable. .
I can't give you the specifics about the tag but I can give you some background to help with your search.
It was the standard engine on full-sized Mercury’s from 1963 to 1970, being found in a variety of outputs depending upon year, model, transmission, and carburetor.
Beginning in 1966, it was an option on the Ford Fairlane and Mercury Cyclone. On the Cougar, it was an available option upon its introduction.
This is a fun read on FE history..
This was my favorite tid bit ..
Also available upon introduction in 1961 was a 375 horsepower version that replaced the 360 horsepower 352 cubic inch V8 used in 1960. This new 375 horsepower engine had a block with a slightly different casting pattern that provided stronger and thicker bulkheads than found in the standard engine. This engine also had an aluminum intake, improved oil passages, and grooved main bearing journals to aid in lubrication. The blocks were dye tested to find any weak areas and the pistons were X-rayed to ensure they were up to the rigors they would likely face.
