Hey guys, just joined the site. This week I purchased a 74 F100 for a restore project. Was told it had a 390 but, after discovering the Y in VIN, I found it's actually a 360 with a 2 bbl. it also has C6 tranny and after taking it out for a ride I noticed the RPM's seem really high at 55 mph. I don't have a tach in it yet so don't know the exact revs. Just sounded really high. Is this normal for a C6?

 

These trucks don't have overdrive so yes it will be spinning more RPM's at 55. My 74 with a 460 and a C6 turns around 2500 at 60-65.

 

On the engine... most likely it is a 360 as built. Still, if the engine was ever swapped, it could be a 390. I believe you can check stroke through the spark plug hole to verify... there are many posts on this topic.

Since you can decode the vin you can figure out which rear axle ratio the truck was built with. This will help figure out cruise RPM if it has the original rear end.

 

Thanks guys. It's the original engine. Entire truck is factory except for the wheels. Only two prior owners.

 

No Overdrive and not even a lock up torque converter, likely 3.50 rear gears at least .... maybe even deeper. Built when 55 was the new national speed limit and gas had been cheap not long ago.

Yeah, to anyone raised with 4s and 6s and ODs ..... it's gonna sound like it's racing at 70.