Spitting/backfiring

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Jan 30, 2012 | 03:54 PM

law2212

Thread Starter

New User

Joined: Dec 2011

Posts: 10

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From: Detroit Michigan

Spitting/backfiring

Hey everyone, i recently replaced the old 2barrel carb on my 1978 f100 302 v8 with a 4 barrel intake and a holley 650cfm 4barrel carb, now that i have it all back togother when i try to start the truck it wont run and occasionally will spit smoke and fuel out of the carb and sometimes flame. i have tried adjusting the fuel and air mixture and advancing and slowing the timing but cant seem to figure it out. any advice would be helpful.

Jan 30, 2012 | 04:13 PM

79F150400M

Fleet Mechanic

Joined: Feb 2004

Posts: 1,509

Likes: 333

From: Arlington,Wa

Double check your firing order. 1-5-4-2-6-3-7-8. Check for vacuum leaks and worst case scenario you have an issue with the valves. How did it run before the swap???

Jan 30, 2012 | 04:27 PM

77393

Senior User

Joined: Dec 2011

Posts: 142

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From: Round Rock, TX

Quote:

Originally Posted by 79F150400M

Double check your firing order. 1-5-4-2-6-3-7-8. Check for vacuum leaks and worst case scenario you have an issue with the valves. How did it run before the swap???

+1
If it was running good when you pulled the old one off, you prob. have the firing order wrong or you stabbed the dizzy wrong. Were you at #1 on the COMPRESSION stroke when you put it in? If its acting like that when you are trying to start it, the timing is off. Check the firing order in a counter clockwise rotation of the rotor.

Jan 30, 2012 | 04:56 PM

OldStyle

Rusty Roller

Joined: Oct 2011

Posts: 1,423

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From: Santa Cruz Mountains

It's real easy to get the order wrong.... We have all done it...

.

Jan 30, 2012 | 05:23 PM

77393

Senior User

Joined: Dec 2011

Posts: 142

Likes: 0

From: Round Rock, TX

If you are sure you have it right and it still won't run, try the HO firing order, maybe somebody changed the cam. How long have you had the truck?
1-3-7-2-6-5-4-8