Of the different grade bolts available such as 5 or 8. what grade is nearest the originals that thread into the block like water inlet, manifolds etc.? thanks
I would have to say grade 5 for the average bolts and grade 8 for holding the inside of the engine and the head. Jim
I would say the original head bolts were grade 2, grade 5 at best.
Same goes for the rest of the bolts.
The original bolts Ford specified were not part of the bolt grading system that followed. However, they were specified as Bessemer Steel which for all intents and purposes was generic railroad steel. Later, Ford used something more equal to 1020 so still a Grade 2/3.
At best, the tensile of Bessemer would have checked out at Grade 2 properties.
Today, I think the lowest Grade the vendors offer is a Grade 5. Some guys claim to use 8's (just because they can) but my brain goes criss cross when they chose to torque them down to the Grade 8 values...
WHY? The threads then see lots more than they are ever intended to see. Until proven otherwise, I STILL think that Ford used oversized tap drills to make machining of taps easier. Adding Grade 5 or Grade 8 torque just doesn't make sense.
George, my '25 coupe has Caterpillar grade 8 bolts for head bolts(that's another story), but they'er not torqued to grade 8 specs. Dave