timing and backfires

[cwhubb]

I searched the threads but I can't find the one I was reading explaining the two events when starting the engine, a puff of air/fuel out of the carb and the fireball back fire. I got both types today (with out changing the timing) when I started my car. The cars not running good enough to use a timing light on it, so I've been playing by ear
thanks

 

[WP29440SE]

its 180* out?

 

[Cranky]

It's actually starting up? Firing order is right? Does the rotor point to #1 when the engine is at TDC on the compression stroke?

 

[daredevil]

sounds like a stuck intake valve.Or its adjusted too tight if the rockers are adjustable.

 

[cwhubb]

the firing order is correct, all ignition parts are new. the car fired up (after I moved the distributor a fraction at a time till I found the sweet spot so to speak) and it didnt miss it actually ran ok, I think the carb may be the problem, but I'm worried if the timings off it'll damage something while warming up to operating temp. I read that you can tell by what kind of carb sputter/backfire if its advanced or retarded
embarrassed to admit that after so many failed attempts to start, it scared the crap out of me when it did, it has open headers lol

 

[bee71]

Mine was doing the same and I found out I had a bad coil.

 

[rsd859]

Be sure to check for vacuum leaks too.

 

[Pops1967GTX]

the firing order is correct, all ignition parts are new. the car fired up (after I moved the distributor a fraction at a time till I found the sweet spot so to speak) and it didnt miss it actually ran ok, I think the carb may be the problem, but I'm worried if the timings off it'll damage something while warming up to operating temp. I read that you can tell by what kind of carb sputter/backfire if its advanced or retarded
embarrassed to admit that after so many failed attempts to start, it scared the crap out of me when it did, it has open headers lol

All ignition parts are New........ "Just because it's new, doesn't mean it's good"
Sounds like it could be a number of things. Narrow down the possibilities. Start at timing, make sure it's correct, sound like the timing is advanced too much Check.vacuum line on the dist, Where are you getting vacuum from?(was there a check for timing slack/slop?) You may also have a jumped timing chain. I have seen a bad camshaft lobe do this too.


then move to carb adjustment
Quoting Troubleshooting Book....
A backfire occurs when there is an imbalance in the air to fuel ratio required for your vehicle to operate properly. If the fuel mixture is too lean (not enough fuel) you may have a backfire in the intake, or too rich (too much fuel) you may get a backfire out of the exhaust system. Most backfires are easily repaired by correcting the imbalance and providing a greater or lesser percentage of fuel to the mixture.

Backfiring can also occur with a sudden drop in fuel pressure. This may be due to a faulty fuel pump or a plugged fuel filter.

 

[Cranky]

More advance usually will let the engine respond quickly and rev up easily and retarded timing will make it act sluggish or even die when you crack the throttle. Being overly advanced isn't going to hurt you when you are trying to get your tune right. I always set my timing at least 20 degrees before TDC for start ups and some get even more. Once the engine is up and running, I then make adjustments but if it's back firing no matter where you put the distributor, you have other problems.

 

[cwhubb]

now its starting without any backfire at all, within two or three cranks. @cranky, the engine was real snappy when I reved it no sluggishness there. I thought it was the carb, it's old and I cant adjust the fast idle either way. it idles pretty fast