Ford Mustang Forums banner

1 - 6 of 6 Posts

·
Registered
Joined
·
117 Posts
Discussion Starter · #1 ·
Hi folks,

I have an '83GL that I am bringing back to life. I've installed an '88 roller block with mild Crane cam, MSD, stock ported intake, ported E7s, and stock 4160 carb. Timing is set at 15 deg initial and 35 total.

I've been out driving it a bit to start working on a tune and decided the main jets (still stock 0.062s) were lean. Full throttle at 3k+ rpm seemed great but it was stumbling a bit at part-throttle highway cruise. I was on my way back in to open the carb when I slowly floored it in 5th at 65 mph and I had a huge through-the-carb backfire. It would not idle after that and smelled horribly rich. I've replaced the power valve and installed 0.064 main jets, but it will still barely start and will not idle. It is obviously way rich because I now have clouds of blue smoke. What else might I have damaged in the carb with a through-the-carb backfire?

Thanks,
Bman
 

·
Premium Member
Joined
·
14,998 Posts
I would go back and double check, sounds like power valve is still blown, or you didn't use a gasket to seat it. Carb is still sucking fuel at idle, it shouldn't.

Depends on how violent a backfire it is, but you can bend throttle blades, might have them not flat anymore and the blades may be allowing a bunch of fuel from the transition slot or even main booster to bleed in at ilde. Typically if the blades are folded though, there isn't an idle...
 

·
Registered
Joined
·
646 Posts
Did you check how much vacuum it had before you bought a power valve?
Don't reuse gaskets.
Also I believe the fuel pump would fail a volume test.
 

·
Registered
Joined
·
117 Posts
Discussion Starter · #5 ·
Fuel pump is brand new Holley standard volume / pressure. I suspect that I have plenty of fuel. I took out a 4.5" Hg power valve and replaced with a 4.5, so I'll make sure I didn't swap them (and put the old one back in). I pulled the carb off and have no evidence of bent throttle plates. Anything else in the carb that I may have damaged / torn by backfire? It is obviously running CRAZY rich at idle now. It will start, but with the pedal to the floor it will only go to 3500 rpm.
 

·
Registered
Joined
·
410 Posts
I would suspect a sticking float. It might not have anything to do with the backfire but something during the rebuild. As bad as it sounds the needle may even be off the float. A piece of trash may be in the seat. Take it back apart and check the float operation and give everything else a quick look-see.
 
1 - 6 of 6 Posts
Top