hi i just started to upgrade my 1980 f150 which had the stock 302 and im moving up to a 351w. tonight i wanted to test it and im shooting flames out of the carb even caught my carb on fire. any hints and suggestions greatly appreciated. i have check over and over my plug wires to make sure there in the right place. i used the haynes 1980-1998 ford bronco and f-series pickups. so i dont know what im doing wrong. i have to fix a leak in the diaphram on my carb and as far as i know thanks for all of y'alls help

 

very little would cause that: 1. Timing (WAAAAY too far advanced) would cause plugs to fire while intake valve is still open.
2. Valves not closing fully(results in extremely low compression too).
3. Firing order might, but I doubt it.
used engine or new rebuild? If rebuilt, is timing chain installed correctly? If old engine, are valves burned/bent?
just a few possibilities, but from experience, check timing and firing order. You know there are different firing orders for different years/engines. Make sure you're using the right one. There are also different distributor rotations. Check that as well. I never had to worry about any of that on a SB Chevy ( waiting to fend off hurled stones and insults ).

 

He's probably right about the firing order, you need to double-check that. Using the wrong order will cause a nice backfire like you're having. In my experience, if the timing is too late, it will also cause a backfire. TK

 

One time yrs ago I bought this '64-1/2 'stang from a guy I worked with. In the cars' heyday, he had the 289 balanced, w/some cam(don't know how big) Edelbrock ect. ect.
Anyways the car sat for 12 yrs without running. So I hooked up an IV(gas from a can gravity fed to carb). I changed the cap,rotor, plugs,wires and I 'rebuilt' the carb. The carb was pretty big.....a Holley, all the bbl's were the same size-he told me it was a 780cfm!!

The whole point is after the car turned over, it was a little shaky. So naturally I look directly into the bowls while I was revving it up. Then it backfired and shot a huge flame into my face burning off my eyebrows and scaring the ***** outa me!! It was damn loud,too. Turns out I had two cylinders with the wrong plug wires.

Hope thats your problem and maybe get a good laugh on my behalf. Late.

 

hey thanx for the info and all i found out that i did have the wrong firing order i thought it was the same as the 255ci cause the haynes manual said for the 5.8L the order for 95 to later and the 255ci say 94 and earlier to i went with the year how wrong i was i went to autozone got my firing order and no s**t it was the same as the 95 and later so i swapped all of my wires and it started have to choke the hell out of it but it runs thanx for the info and your time THIS IS THE BEST BOARD EVER