I have a 302 (at one time I looked up the serial number) and it has a 351 firing order. Is that right. I should add the the manifold has the 302 firing order.

 

It's certainly possible to have a 351/HO firing order in a 302 all it means is a cam change. What vintage motor and vehicle is this?

 

I belevive it is around a 78 and I installed it into a 55 f100. This engine has run great up to a couple of weeks ago and now it misses and back fires. Sofar i have changed the plugs,distributor cap and rotor. No help there. I think I will pick up a distriutor today.

I might say it runs so rough that I can't see the mark to check the timing. I looked at all the vacumn lines and could find no leaks. It seems that every time I drive the truck the missing gets worse.

 

Have you tried the old firing order just to eliminate the possibility and are you sure you have the plugs wired correctly for either one, the cylinder numbering sequence in different with a Ford than a Chev or Dodge.