Back fire through carb..

[CFMopar]

When I get on the gas at idle it will pop through the carb somtimes... This is cause its running rich no?

Guess check the floats and jet down?

[grouseman]

Nope.  You've likely got a spark event happening when it shouldn't.  Unlikely but possible is valve or cam problems, but I'd focus on the ignition side of things first.  Check the dist. cap, look for crossfiring plug wires, etc. 

[firefighter3931]

Vic,

It could also be going lean off idle. Check the ignition first like Grouseman said and eliminate that as a potential problem....then look at the carb. 


Ron

[Chryco Psycho]

usually it is lean off idle so you need a larger squirter int he carb to eliminate that

[deputycrawford]

Deffinately check timing. Idle timing, maximum timing, firing order, How fast maximum timng comes in. The works. Check vacum at idle, etc. see if it jumps around. You might even have a vacum leak that can cause lean conditions at certain times. Then put a bigger squirter in there.

[grouseman]

I just realized.  What kind of a carb is it?  Are you STOMPING it from idle to get the pop, or is it any kind of aggressive start from idle?  Is there any indication of an off-idle bog? 

[CFMopar]

No not stomping on it nice and easy

I'll run through the checks today

[myk]

I just realized.  What kind of a carb is it?  Are you STOMPING it from idle to get the pop, or is it any kind of aggressive start from idle?  Is there any indication of an off-idle bog? 

I'm still dealing with the pop from off idle, and off idle bog-I will have to try drilling out the squirter in the 'eddy as you can't change squirter sizes...

[Ghoste]

Carter used to offer a few different sized squirter nozzles, have you tried looking for any?

[Chryco Psycho]

Eddy has a pack of 3 squirters small stock & large
compared to what 14 or so for Holley 

[myk]

Lol....All of this time I thought I needed to change the accelerator pump plunger.  It's the damned squirter I'm supposed to change?!  I'll order that ASAP and get back to you guys with the results...

[Chryco Psycho]

Okie dokie

[Lord Warlock]

I've had a car backfire thru the carb before due to the timing being too far advanced.  Not sure why, but once i adjusted the distributor to retard the timing it stopped doing it.   Course in my case it was my car from hell 70 camaro w/350, and the flameout burnt a circle in the brand new paint on the hood.  It could have just been an ornery POS car getting even with a mopar owner.

[Ghoste]

It could have just been an ornery POS car getting even with a mopar owner.

  That's what it was I bet.  If you can't beat 'em or get the rules changed...

[myk]

Eddy has a pack of 3 squirters small stock & large
compared to what 14 or so for Holley 

LAAAAAAAAAAAAAAAME.

It's even worse than you think-that 3 pack of squirters contains these sizes: tiny, smaller than stock, and JUMBO.  I'll get the jumbo size in and see what happens.  If I had spent this amount of time working on a Holley I'd be a 'pro at this by now.

Oh, and one of you guys mentioned vacuum readings and checking to see if they bounced around?  I disconnected the hose going from my intake to the brake booster and attached that hose to a vacuum guage-I got a reading between 15 and 18, with the needle shaking pretty rapidly between those numbers.  Is that normal?  If not, then what is that and how badly am I screwed? 

[dodge freak]

But you can drill those tiny holes out a little. Not with a drill motor but by hand. Those tiny drills are called wire drills they come in sizes .020-.050+ every 1 or 2 thousands of an inch .001 and you get whats called a pin vise or drill holder to spin it. The pin vise is $5-$10 and the drills are like 50 cents to $1 each. Only a good tool shop has them but they are worth getting , this way you can drill whatever size hole you need. They even go up over .050-.100 and higher if you need to open the jets up but some people say thats not a good idea but if eddy does not have what you need or its a RIP off I would open the jets up too , just make sure you have a spare set. You should only go up a few thousands at a time, once you go up in size you can't go smaller.

[Chryco Psycho]

you can go smaller , they are brass just solder them & start drilling again 
the vacuum reading should be steady not bouncing 3" not a carb problem

[myk]

Well, I'm trying to go larger on the squirters, as I'm pretty sure that I have a lean condition going off-idle.  I just think it's wierd that they would include only 1 size that's larger than stock.

I was pretty sure that the bouncing vacuum reading wasn't right.  What could that mean?  Did I hook up the guage properly?  Are you supposed to keep the intake to brake booster hose connected while you take your vacuum reading using a T-fitting?

[dodge freak]

What do you mean brass, what are they called and what size are they? I guess you just jam them in the hole , right ? I have a few metering blocks that the power valve holes I open up to much for my motor that be great if I can resize those holes agian. You got me thinking, thanks

[dodge freak]

Maybe a bad valve or a sticking one, not too sure but a vacuum leak would not cause the vacuum to bounce. Lets see what the motor pro's say.

[grouseman]

I don't know if the brake booster line is maybe pulsing because you're connected to a single runner.  Do you get the same bouncing when connected to the Full vac port on the carb?  If so, I'd guess a valve isn't closing tight. 

[myk]

Full 'vac port?  Hmm...Would that be where the vacuum advance is supposed to hook up to?  If it's a bad valve or something I'd welcome it as an excuse to tear down the motor and build it MY way, instead of trying to tune someone else's problem.

Meanwhile, I put in the larger squirter for the 'carb and the hesitation/bog/stumble whatever you wanna' call it is 99% gone.  I've also, jetted up the primaries and metering rods 1 size, so I'm figuring on addressing my ignition for any more improvement.  I was planning on jetting up the secondaries but I can't seem to get them out of the 'carb-they're stuck!  Llol...

I've gotta' say thanks to all again-it certainly isn't perfect but this car hasn't run this well in the 12 years that I've owned it...

[Chryco Psycho]

I assume you checked the float level while it was apart ?
raising the float level slightly can help eliminate a bog as well

[myk]

Yeah I did!  I didn't know where to adjust them to so I just put them to 'spec hang and drop, which is 7/16" hanging upside down, and about 1" drop.  Do you guys recommend a different setting? 

It's a good thing I checked the floats too as they were WAY off...

[Chryco Psycho]

raise it 1/32 -1/16

[myk]

I'll try it-feels like a long shot, but I'll try it.  Considering that I got the vacuum readings that rapidly fluctuated between 15 and 18" I'm starting to fear that I've got internal problems, unless I'm taking the vacuum readings incorrectly...

[resq302]

Eddy has a pack of 3 squirters small stock & large
compared to what 14 or so for Holley 

Oh, and one of you guys mentioned vacuum readings and checking to see if they bounced around?  I disconnected the hose going from my intake to the brake booster and attached that hose to a vacuum guage-I got a reading between 15 and 18, with the needle shaking pretty rapidly between those numbers.  Is that normal?  If not, then what is that and how badly am I screwed? 

I too have noticed that with my engine.  On my 70 El Camino, the vacuum gauge holds steady for the most part.  On my charger, the gauge really bounces around but the engine seems to run ok.

[Chryco Psycho]

where did you hook the vacuum guage up to ?

[resq302]

The vacuum port on the back of the intake manifold where the vacuum line that goes from the intake to the power brakes.  Like the above post, I disconnected the vacuum brake line and attached the vacuum gauge to that fitting.

[Chryco Psycho]

it is more likely to bounce there than a port on the carb so you may not have any problems

[resq302]

Ok, my stock carb only has two ports on it.  One for the vacuum advance for the distributor which I think is only a metered vacuum (from what I heard) and the port for the pcv hose.  Which one should I hook it to?

[Chryco Psycho]

the PCV connection if possible

[myk]

where did you hook the vacuum guage up to ?

I don't know where Resq hooked up his vacuum guage to, but I disconnected the hose from the intake to the brake booster and hooked it up to my gauge.  Am I supposed to leave the system connected and install a T-fitting for the gauge instead, leaving the intake and the brake booster connected?

[resq302]

I think what Chryco is saying is to disconnect the pcv hose and get a reading for vacuum at that port as it should be more steady. 

Where I disconnected my vacuum hose was at the fitting behind the carb and on the top rear section of the intake manifold.  I installed a vacuum hose from my gauge to the fitting on the intake and took the reading there which was bouncing like you had said.  I will recheck it from the PCV port on the carb when I get my car back from the body shop hopefully on Monday.

[myk]

PCV port huh?  Well I'll give it a shot!