Good afternoon all
Got a 283 automatic, put on new 1106 Edelbrock, 600 Holley, cap, wires, plugs, coil ect.... timed it by ear cause light broke. Starts right up and runs smooth. When you accelerate slowly runs smooth when you accelerate quickly backfires through carburetor. Pulled carb and put in new power valve everything else looked just fine. Put it back in and still the same. Any suggestions

 

Probably not the carb, more like a timing issue. Get a light and find out if the timing map is right.

 

Double check your plug wires. Make sure you got them all back right.

 

the carb could be lean.

 

backfire through the carb is almost always timing...consideirng you timed it "by ear," I would definitely say that's the problem...

 

 

IF its an actual backfire. however I've seen people chase what they thought was a backfire when it was a lean pop through the carburetor. being that the o.p has added a new carburetor it is something that should be checked too. out of the box these carbs calibrations are on the lean side.

 

Is this a new, as in new in the box, never been used carburetor or just new to you?

 

X2 on ckg firing order. Bet 5 and 7 are reversed;happens to the best of us

If it is in fact the wires are right and you did time it try backing the idle mix screws out 1/4 turn at a time see how she acts. One thing at a time

 

backfire is a fire in the cylinder with the intake valve opened.

wrong firing order, carbon on cap, plug wires sparks jumping around, bad condenser, bad coil, open in a plug wire.. make sure your ignition is correct before you go chasing down a carb issue.

my best advice? ..buy a light... don't time by ear.

 

3 requirements for the engine to run in no particular order..

1. Fuel
2. Fire
3. Timing

With the backfire, probably timing. This said, it only takes one backfire to pop a power valve on a Holley. Even a brand new shiny one.Just a thought!

 

I run a 600 dp and also had a backfire. I cured this by changing the squirters, jetting, pump cams, and a "Lars vacuum canister" timing curve.

The dip is a rich bog from the squirters and fuel would puddle and could ignite in the manifold.



My final setting are below. At 67 on the primaries I was getting a bit of a lean surge at cruise. The 69s cured this.

331 CI, pump-friendly 9.5:1 CR
K&N 14"x4" air filter, Corvette drop base and lid
Holley 600 dp, choke horn milled and blended, Primary - 69, Secondary – 74, Squirters - 21
1/2" Aluminum open spacer port matched to manifold, exterior polished
Edelbrock Performer RPM intake manifold, port matched, exterior polished with all extraneous castings and lettering removed
Homemade lifter valley splash shield to keep hot oil off manifold bottom
Manifold heat riser crossover blocked
Camel hump 1.94/1.50 heads hogged out to 2.02/1.60, pocket ported, port matched, pump-friendly hardened seats, 3-angle valve job
Cylinder bores clearanced to unshroud the valves
Comp Cams 1.52:1 roller-tip rockers
Crane Cam Vintage Muscle 327/350 hp cam, 222 degrees @ 0.05, 0.447" lift (with 1.50 rockers)
Doug Thorley headers, dechromed and ceramic-coated
2.5" mandral-bent exhaust (including tips), 2" cross-over just before rear axle
DynoMax stainless Ultra Flow mufflers
Millerspeed 1-1/2” Gilmer under drive belt drive system
Mallory Hyfire IV CD ignition box triggered off Accel points
Mallory high voltage chrome coil
Mallory spiral-wound coil wire
Mallory solid copper plug wires, ends soldered to wires
Champion plugs
37 degrees total ignition advance
Carter high volume fuel pump
Melling high volume oil pump
Open breathers
Polished aluminum high flow water pump
160-degree thermostat
Flex fan with polished aluminum spacer
Polished aluminum one-wire 100 amp alternator
Header Power Bracket
Keisler TKO600 5-Speed
Hurst shifter
3.70:1 positraction with Big Block yokes
225/60/15 Firestone Firehawk SZ50s on 7”-wide Western 30-spoke Turbine Wheels

 

Thanks for all the advise so here's what I've decided to do. The Holley is new right out the box. Buying a light and an Edelbrock 1406, the same that's on my 1980 and have never had a problem. My brother who is a big Holley fan is buying the Holley. Looks like everyone's happy, I'll let everyone know how it goes and thanks again

 

Put the Edelbrock on and was having the same problem. So started rethinking the issue and after checking everything here was the problem. There was not enough volts getting to the coil. I ran a wire from the battery to the coil and no back fire and started right up. Sooo I replaced the points with an electronic ignition, rewired the coil to a 0-12 volt wire and have no problems since. Ohh put it on a timing light and it was right on. Thanks everyone and it's been a joy being behind the wheel again.

 

If you are driving fine and hit the throttle and it back fires through the carb it is known as lean popping.

The carb needs to have the squirter arms adjusted so close that with the motor off that even the slightest throttle movement causes the squirters to dribble.

 

Well, this certainly backs up the "90 percent of carb problems are actually ignition problems" theory.

Scott