Hot Rod Forum banner

1 - 11 of 11 Posts

·
Registered
Joined
·
38 Posts
Discussion Starter #1
I've got a 82 Mustang Coupe. I installed a 87' 302 HO. I did a compression test right after the install and had between 150 and 135 psi on all 8 cylinders. I have the correct HO firiing order and wired correctly, freshly rebuilt 1850 holley(stock #66 jets) 600 vs. The timing is set at 14*btc.

The problem: The engine backfires through the carb only upon startup and is difficult to start. Sometimes a fog of fuel mists out of the carb between starting attempts.

Once the car is started it runs wonderfull. I can run it up to 5500 rpm's between shifts flawlessly with not even a miss.

What the hell is causing the backfiring on startup? I hate it! I won't drive the car anywhere because I'm embarassed the damn thing backfires like that.
 

·
Member# 3287
Joined
·
2,625 Posts
Carb backfires to me mean an intake valve is hanging open or a timing issue.
 

·
Administrator
Joined
·
18,399 Posts
Is the choke closing?

If the choke is wide open when the engine is cold, it gets too much air and backfiring can happen......and is also hard to start.

Try closing the choke to start.
 

·
Registered
Joined
·
38 Posts
Discussion Starter #5
The engine is most definately an H0 engine. E7 heads all roller components and XXX casting in the lifter valley.

A few things I forgot to mention. The choke horn has been removed as this car will be more dragrace use but will see some street duty.
 

·
Administrator
Joined
·
18,399 Posts
quick50stng said:
A few things I forgot to mention. The choke horn has been removed as this car will be more dragrace use but will see some street duty.

Then, you might as well get used to it....................
 

·
Registered
Joined
·
38 Posts
You could watch a vaccum guage while its running to double check the running condiiton. Could be a pumped up lifter or weak valve spring. My car has no choke and takes a little bit to motivate it but its not that bad.
 

·
Race it, Don't rice it!
Joined
·
7,734 Posts
Choke or not you should not be getting lean popping. Check timing, plugs, rotor...ect... and insure, actually check, not just think they are okay. What happens if you pump the throttle several times?
 

·
Registered
Joined
·
38 Posts
Discussion Starter #10
I am using a brand new NAPA distributor for an 85 Mustang Gt (roller cam compatable, duraspark ingnition module/box, new ford motorsport 9mm wires new cap and rotor.

The distributor was stabed it on top dead center compression stroke at 14 degrees and running the HO firing order counter clockwise from 12 o'clock(where the rotor points)

And remember it only pops while trying to start. Once it starts no problems.I am going to go back through and thoughly check all the ignition components again maybe I have a cracked spark plug or something stupid like that.

Thanks
 

·
Hotrodders.com Moderator
Joined
·
6,391 Posts
poncho62 said:
Then, you might as well get used to it....................
Yup, cold start with no choke you can experience a lean pop through the carb. If it was a plug or wire it would show up more under load. It probably wouldnt hurt to re-check your timing also.
 
1 - 11 of 11 Posts
Top