[80cobra]

Hey, I was wondering if you guys had any idea whats causing my engine to back fire. I just rebuilt an 87 roller cam 5.0. I converted it to carb, I used the original cam, a distributor out of an 85 mustang manual trans, and the original factory exhaust. the problem is it wont run on the HO firing order but will run on the non HO firing order, but back fires at idle and over 4000 rpms. I was thinking I need to get the distributor recurved but dont know for sure. it has a performer 289 intake and a holley 4150 vacuum secondarys and I am using the ol duraspark electronic ignition. thanks for ya help.

 

[Jarrett]

What firing order are you using, and what year car is it in?

 

[STINGREY]

dude;if its an ho it should run with the 13726548 firing order,althugh it will start with the non ho firing order she will never run right and backfire.try the ho firing order again and double check your work.

 

[speedytang]

If you used the Original Cam you need to use the HO Firing order no way around it. Also make sure your using the correct cam gear on the distributor or you will eat up the gear or the cam.