ok i can ease into the throttle and its cool no problem as soon as i punch it it starts backfiring and stumbling and makes no power justa strong vibration no black smoke out of the exhaust motor is slightly fresh heads cam intake manifold carb distributor and now when i get on it just bleh, it sucks... this happens at around 2500-3000 rpm

 

A good place to start is the plugs, and the timing.

 

Check plugs, wires, timing, powervalves, and fuel pressure.

 

checked the plugs there just a little ashy i do have the wires zip tied together and i have an edelbrock 600cfm carb manual choke also the main fuel line looks like it has a heart beat, that cool? like you can see when its pumping fuel and when it isnt in intervals almost like blip blip blip blip blip maybe thats the problem? oh and whats a powervalve?

 

In my experience, backfiring is usually an ignition problem - and it's the easiest place to start. Check the plug wires, make sure all of them are ALL the way on the plugs (I had one that would slip off just enough to cause bad spark, but not enough to even tell - this caused the same reaction in my car as what you described). Also check for continuity in the plug wires - I also have had broken wires straight out of the box in the past. Double check the firing order, and check the timing.

 

where is the timing set at? if it's too far retarded, it'll do what you're describing.

 

That sort of information up-front is always a good idea.

Probably not "the" problem, but I wouldn't call it a good situation.

Something in a different type of carb than you have that was mentioned because at the time we had no clue what type of carb you have.

Tell us about your distributor.

 

i have an hei jegs distrubutor (vacum advance) with a moroso cap rotor and wires and a msd coil im at about 6 degrees advanced i really messed around with it today and my friend reved it up to about 5100 and it was back firing out of the carb also one of my plug wires burnt up a bit on the header and is now exposed a little its too late to do anythign now i'll have to do it tomorrow morning when i get to my shop i tried retarding the timing a little bit but still nothing i spent way too much cash as an 18 year old to have this thing crap out on me please please please please help me out here this sucks
and i have ngk v power plugs i gapped them at .5 oh and my overall timing is around 45 if that matters

 

I think a .050" spark gap is pretty big. I'd say use something like .040". Also stick with cheapy delco plugs, the gimmick ones only help with wallet lightness. (just in the future, no need to tear them out now..)

know what the cam is?
i'd bump up the initial timing. Maybe try 12* and see how that works.

 

That wouldn't help anything - that wire could easily cause a problem.

Try advancing it some - mine is set at about 10*BTDC

Like mentioned - try a smaller gap

LOL - are you kidding me? 18 year olds have more money than anyone on earth! I had way more money in my pocket at 18, and I had already left the nest! When you get to 41, lost everything you own to your ex-wife, AND pay her enough in child support for your 1 kid ... to support 3 kids, then we'll talk about cash flow!

 

Are you doing these timing checks with the vacuum advance hooked up? I suspect you are. 12 degrees BTDC at idle, 36 BTDC max at high RPM, with the vacuum disconnected and plugged, is typically about right for SBC's.

 

lol ok your right about the cash thing my apologies i have a comp xtreme energy cam
Lift: .462''/.469''
Duration: 262°/270°
RPM Range: 1300-5600
does anybody think it may be running lean the fuel pump is still stock and i have a aftermarket cam and carb and it back fires out of both ends i dont know anything about carbs and the vacum advance was plugged

 

mine did the same thing when the timing was retarded too far. I set my timing with a vacuum guage... lol. when i need to set mine with no tools, ussually a good place to avoid backfiring is to advance the timing until you can hear the engine slow down the starter upon starting (when engine warm) then back it up just enough so the starter isnt working hard anymore... also make sure your vacuum advance is working... hold your finger over the port where it is plugged in to the carb and rev the engine, you should be able to feel a small amount of vacuum... and ofcourse a smaller gap... 35-40 thousandths should be plenty.

 

Vacuum advance and fuel pump are not in play when you go WOT. If it wouldn't idle or got poor fuel mileage, the vacuum advance may be a problem. If it bogged down at WOT after first running fine, it might be a fuel pump problem. I'm not seeing either one of those in the description of the problem.

Timing is very critical. Have you replaced the harmonic damper or the front cover? GM used a timing tab at the 12 o'clock position on the front cover as well as around 1:30 o'clock, and if you have a damper made for one and a tab for the other, there's no way you can properly set the timing. The most common situation is a 12 o'clock damper with an engine or timing cover change to the other tab, so that what you think is 6 degrees advanced is more like 30 degrees retarded. It may run because the vacuum advance gives you enough to at least get it in the ballpark, but when you drop the throttle (which drops the vacuum and therefore the vacuum advance), it sputters and complains.

On the other hand, 6 degrees BTDC instead of 12 degrees BTDC may be enough to make it unhappy.

 

how would i go about determining whether i have a mis match with the dampener and timing cover i'm gonna try advancing it some more and give it a go

 

Where is your timing tab?

The easiest way I know is to look at the keyway in the damper. If it is a 2 o'clock (I'll call it, for ease of typing) type damper, the TDC mark and the keyway will be almost lined up. If it is a 12 o'clock type damper, the TDC mark will be straight up on top when the keyway is lined up with the driver's side cylinder bank centerline (the keyway in the crank snout is lined up with the 1-2 cylinder crank throw).

You have to pull off the front pulley and the damper retaining bolt/washer to see this.

 

the timing mark and the keyway are the same the timing tab is off to the side at about 2 oclock i know that the keyway holding the damper is lined up with the timing mark

 

Then you should be in good shape as far as being able to set the timing properly.

 

Im assuming your distributer has a vacuum curb kit unerneath the rotor. If this is correct there are weights underneath the rotor that stretch outward upon acceleration. Small springs determine how much or how little the weights extend outward to advance your timing after the vacuum advance is at its max. The weights sometimes stick in or out making it hard to time. Try taking your cap and rotor off and turning the the rotor mount and releasing. it should turn smoothly and return to it's original position. You can purchase a curb kit at about any parts store for about ten bucks. It will come with three sets of weights. There is a chart on the back that will explain which spings to use for what power range your engine runs at.

 

ok i'll check out that wieght thing and i'll try advancing my timing some everybody keeps telling me i run reall rich i havent really driven the car so the plugs really havent had time to gum up alot i was thinking about ordering the recalibration kit for the carb it comes with five sets of jets and metering rods and other stuff anybody think that might help

 

any opinions at all i would like to get this running properly so i can feel somewhat accomplished. lol

 

Does it clean up and go if you hold it down? Or continue to backfire?

 

i dunno i havent really tried to keep on it

 

If it cleans up and runs after it backfires while hold it to the floor it could be your acell pump shot is insufficient. If it does not clean up it could be an insufficient fuel supply. Mike

 

well today my buddy at work was adjusting the carb and he screwed the fuel screw in all the way and it didnt stall kinda weird

 

i advanced the timing to 12 degrees and still does the same thing i did romp on it and it doesnt really clear up its hard to explain im gonna down the jets tomorrow and see what it does

 

you have way to much total timing if it is 45 deg. with vacuum advance on hooked.

 

Your 18?
Son...you got a lot of learning to do.

This not rocket science, you just need to learn the basics of how all this stuff works together.
{Edited by Moderator}

There is professional help available, you just need to know where to find it.

 

problem fixed i got a new distributor and the msd 6al box no more backfiring no more choking car runs like a champ

 

Moral of the story: When you have a carb problem, two steps are required to solve it:

Step 1: Fix the ignition.

Step 2: Go back and do what we said in Step 1 before you touch that carb. . .

 

it's true on a 69 camaro with a 454 too. the advance weights were a lil worn and stickin. it has a FULL msd set comein. with a zl-1 intake.

 

"Ignition first Carb second"..where have I seen that before?

 

that is the coolest smiley ever created