302 Trouble

[timothyt973]

Hey, I'm having trouble with my 302. Let me start by saying I'm not a mechanic, this is a hobby. Anyway, I recently had it rebuilt professionally and put it back in with some help and got it going. Ran great for a couple of weeks while breaking in and then started popping under power. By popping I mean out the exhaust like back firing but not quite as loud or violent as back firing usually is. I've gone through everything like plugs, wires, timing, and nothing has helped. I'm running an electronic distributor from wild horses, a Weiand intake manifold, a Q-jet and headers from Duff. Aside from that there's nothing really fancy, pretty basic. I know Q-jets aren't well liked, but it's brand new has worked great so far for me. I've had the timing from 9 degrees all the way to almost 20 and it seems to run best around 16 degrees. Idles great and runs wonderful at low rpms in the trails and even at higher rpms in the trails, like running through mud or up hills, but on the road anything over say 30, 35 mph it starts popping and hesitating or kinda surging. Any help or ideas what to try next would be awesome, Thanks

Tim

 

[davebonnie]

Have you tried a higher octane gas?

 

[broncomaster]

Was the bronco sitting along time. The quality of the fuel has alot to do with runability. The popping you are talking about points me to the valves are they adjusted to tight? Also surging and hesitation sounds like lean condition. Has the carb been gone thru and cleaned.

 

[firemedic]

Popping and surges, did you have the timing gears replaced? On a 73 if its original, the larger gear will be metal with the plastic coating on the teeth. If that gets worn or broken it could throw off timing Check the chain also. Hope it isn't one of those, since you already had the motor out and worked over.
Hoping it is something simple!!!!!!!!!!1
Tim

 

[broncnaz]

Might be float level is to low in the carb. Or you have a different problem in the carb just cause its new doesnt mean its good almost all carbs need some tweeking to get them to run right. You could have a problem with the secondary air valve trying to open to soon might be causing the back firing.

 

[PaulS]

If you retard the timing back to 7 or 8 does the popping go away?
Does it still surge?
Usually backfiring (popping) in the exhaust is valve related but the surge is timing or lean fuel oriented.
You might have two problems.

 

[Kenny]

Fuel filter?

 

[timothyt973]

Ok, so I have tried higher octane fuel, and a new fuel filter. I'll go through the carb with some gum out and blow it out maybe something got lodged in there, I don't think it's to far outta wack as far as adjustment only because it was working great before the rebuild and right after. The valves catches some interest, is this something that could change during the break in period? But no one is leaning towards ignitions problems? I'm just trying to rule out stuff at this point. Thanks for everyones ideas, I'll keep trying and keep you posted.

Thanks Again

Tim

 

[paleo man]

is the dist. vacum advanced??...are the springs/weights working??....check fuel pump/filter??....check fireing order....when setting timming did you pull vacum line off dist. to set? or did you set with vacum line connected?...carb float set to low? starving engine?......paleo man

 

[iwlbcnu]

I be looking into the cam, the oils now a days are causing alot of wiped cam lobes on rebuilds from what I have been reading.

 

[garberz]

Years back, I had a F250 76' Dura spark ign. Close to the same symptoms as yours. Turned out to be the coil wire. Simple fix after I figured out what it was, and blew both mufflers apart.

 

[Carl]

Maybe check the spark plug wires. Make sure they are in the correct order and are fully connected. A couple of times one or two have loosened up on me at the distributor making it run very poorly. I would also check spark plug gap.

Like PaulS mentioned above, it wouldn't hurt to check your valve lash.

 

[Kenny]

Come to think of it, I had a similar problems when a badly crimped connector to my Jacobs ignition decided to start acting up. Very hard to find since I couldn't tell by looking at it. Try pulling on all of your ignition, starter solenoid and battery connections/wires/cables, and look for looseness. Also look for corrosion.....especially on the battery terminals. If your battery terminals are clamped onto the cables with a nut and bolt, replace them with a set of cables that have the terminals crimped (cheap at auto parts store).....sometimes corrosion builds up inside the clamp/cable that is hard to see.

 

[MustangHowie]

Years back, I had a F250 76' Dura spark ign. Close to the same symptoms as yours. Turned out to be the coil wire. Simple fix after I figured out what it was, and blew both mufflers apart.

Same problem I just had with my '84 F150 351W. I thought it was condensation in the tank. Turned out to be the wire from the coil to the dist. I didn't blow out a muffler, but I did scare the dogs.

 

[Flintknapper]

I be looking into the cam, the oils now a days are causing alot of wiped cam lobes on rebuilds from what I have been reading.

Yup,

Cheap cam wiped out during break-in. Or needs valve adjusted....would be my guess.

 

[timothyt973]

Ok Good news, turns out it was a bad wire. Running much better now, thanks again.

Tim

 

[garberz]

Ok Good news, turns out it was a bad wire. Running much better now, thanks again.

Tim

Was it a bad coil wire?

 

[cdub0451]

I had the exact same problem and it turned out to be the Ignition Control Module wires were cut just a little but enough to cause the same problems you were having. I discovered this after replacing pretty much the whole ignition system.