Carlos.....

Hey, sorry if I sound like a complete idiot but, I just got a 65' mustang and it's a project car for me and my dad.
We spent hours trying to get the thing to start with the 289 firing order and the intake manifold says 289 but after like 3 hours screwin with it we decided we'd try something different andso we tried the 351 firing order and fired right up.Does that mean my car's a 351 or is that some rediculous coincidence?

jtmustang

351 or 302 ho...and i think boss 302's too

mjr46

first thing I 'd do is check casting number on the block down by the starter and see what year block it is..if it's still a 289 then someone has swapped cams for an h.0 firing order cam

mjr46

oh and if intake says 289 on it you don't have a 351 cause 289/302 intakes are to small for a 351= don't fit

r.barn

It means your 289 has an "HO" firing pattern.

the "HO" 302/289's run a 351W firing pattern.