I was in a junk yard today that had a 57 mercury with a 312 engine.the owner told me that the 57 merc. had a higher rocker arm ratio than the 57 ford which is 1.54.but didnt know what it was.i thought 1.54 was the highest for a stock y block.i didnt take the valve cover off to check for part number.any opinions on this   carl

I think that all 312's had 1.54's, I have one that I pulled out of a 63 Ford 1 1/2  ton log truck with Merc valve covers that has 1.54 ratio. Of course this engine had been swaped into the old pulpwood truck at sometime. The block was no good (cracked), but I got a decent set of G heads from it

Glen Henderson



Freedom is not Free

Letohatchee, AL

The rocker arm history is this;  '54-55, 1.43 with slotted adjustment screws and locknuts.  '56, 1.54 with slotted screws and locknuts.  '57, 1.54 with self locking adjusting screws, '58 and later, 1.43 with self adjusting screws.  Mercs had the same arms as Fords each year.  Cubic inches had no bearing on the rocker ratios, only the year of manufacture.

John

John - "The Hoosier Hurricane"