I came up a little short on my search for a set of down pipes for my 70 FB with 302. I'm not interested in H or X pipes,. What am I missing - is the 2" too small, factory manifolds or w/out X/H too limiting? Thanks, Tom
REally depends how you drive the car. If you are just tooling around town with a stock automatic not worried about high RPM power, you would probably be fine especially if you are going 2 : 1 below the motor.
At that point the exhaust gases are hotter then later on in the exhaust. With hotter gases or exhaust, you can run a smaller diameter pipe. The as gases get hot, they become less dense put higher pressure.
If you look at high end specific built headers, they'll be what's called "step headers" the first several inches of tubing will be smaller then step up to a bigger diameter. You enemy is going to be compression bends and lousy mufflers.
I don't believe Ford actually offered dual exhaust on a non Boss 302 for 69&70. But I believe some muffler chains did. I actually have a Midas Muffler 302 dual exhaust H pipe. It's 2.25". I bought it for a project but never used it. It's brand new, never used. If you're interested in it let me know. Unfortunately with COVID I'm stuck 150 miles away from home. It would be a few weeks I'm going to say. If I find a picture I'll post it
To my knowledge, Ford didn't change the exhaust manifolds for the 302 from the '65-style until '71, so the "H" pipe is going to be the same one from '65-70. From there, your choice will be whether you have the "log" manifolds installed on all 289 non-HiPo and 302's (except BOSS) or the HiPo style.