Carb backfiring

[bmg]

Man i need some help on this. Recently put a truck avenger 550cfm on my 70 350 30 over motor with rv cam and hei with 350 turbo. For the life of me i got a timing mark on it and well lets say i don't think its the right one cause its bout 33 deg off. this mark is to the right at about 2-3 o clock looking at it from the front. with a scope on it when it runs the best the mark on the balancer is right under the top of the water pump. now how in the hell can i see or put a timing marker there? is there any other way to tell if it jumped a tooth? also i have a clear fuel filter (big en) comin off the gas line just before it enters the carb, is this suppose to stay full all the time? i think that is why i am gettin the backfires cause there is not enough gas gettin to the carb. does this mean a bad fuel pump or somin else? sorry for all the questions but really need some help.

also anyone got a fabrication to that dam ac flapper in the diversion box or i gotta by a whole new box?

[69ride]

i have seen a balancer slip before. the rubber between the inner and outer ring slips and the timing can appear to be off. don't trust the balancer. then again i've only seen this happen once

[Chevy Wrench]

I've seen the balancer slip quite a few times. What I would do is pull the #1 spark plug out. Rotate the engine (by hand) until the piston is at t.d.c. Next, pull the distributor cap and see if the rotor is facing the #1 cylinder. If it isnt, rotate the engine 180 degrees, then check the rotor again. If it dosent line up in either positon ( of the piston) then the disributor is off. Backfiring through the carb usually means that the firing order is off or the timing is way off. It wouldnt hurt to double check the firing order before you start working on it. Good luck.
John

[Chevy Wrench]

As far as your fuel pump, is there an air bubble at the top of the filter, or is it completley empty? If its just an air bubble, this is normal. If it is empty or close to it, then I would say you have a fuel delivery problem. Not having enough fuel to the carb would not make it backfire. Or at least I have never seen it happen, and I work on cars and trucks everyday, its my job. Although, most of the problems I incounter are map sensors, o2 sensors, tps, ckp sensors, etc, etc, etc. Everytime I look at an old V8 now, I get lost trying to find the DLC port....hehe

[jhow66]

Sounds like you got the wrong balancer for you timing tab. Most later model engines (blue-305 & 350) had timing tab straight behind water pump. Timing mark on balancer was where you discribe. Low timing will cause a carb backfire . Just advance your time until it goes away and if it starts alright without drag leave it there.

[bmg]

cool will check out the timing today if the balancer did slip what one do i put on it just a reg 8" so i can use the timing marks at the 2-3 o-clock position. The filter was completely empty after i got back from a ride then started filling up slowly when i pushed on the throttle nothing fast tho took bout 2 min for it to fill back up.

[bmg]

how can i get more fuel delivery to the carb, cause when i press the throttle its hesitates then finally goes or somtimes will backfire and stall.

[LudwigTheMad]

higher flow fuel pump....also you said you replace the carb....what fuel pressure does your new carb require...

for example holleys like 6lbs and quadrajets like 8lb....or is it the other way around????

you also may just need to adjust your carb....this can be done with a vacume guage or by ear........i

If you use a vacume gage, connect to a steady port (lower side of the carb) and adjust your fuel mixture, reading the guage...when it starts to go down, stop go the other way, when it starts to go down again, turn back till you have the highest vacume-then your adjusted proberly.

after you do this, make sure your idle is adjusted back to normal and repeat your check.

otherwise make you mixture a little richer (small turns) and see if it stops....sounds like you mixture is to rich....(carb backfire is too lean.....regular backfire is too rich....someone double check me I might have that backwards....as personallity #7 seams to be strong influance today)

by the way #7 is the backwards one.............I think

[bmg]

changed the plugs today also take a look at these.....also i keep loosing rad fluid and it not hitting the ground and no white smoke outta the pipes..i do have small bubbles in the radiator tho is that any sign of a small leak in the head gasket. changing the oil here in a few also.

[bmg]

that pic sucks

[bmg]

another

[bmg]

2

[bmg]

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[bmg]

any idea where the antifreeze is goin? its not comin out the tail pipe at least not white smoke, its not comin out the blowby vent. i got it to stop backfiring i think the adj to the distr moving it a lil and adjusting the carb lean rich and choke setting took care of that prob. fuel filter seems to be staying full now, not sure what i did to do that maybe the carb adjust. the oil was not as black as it usually is(only 4 months on it and less than 2000 miles). thanks for all the input guys/gals. just need to fix that anti freeze ghost. any other way to find out is a head gasket is goin out? no oil anywhere.

[bmg]

any ideas anyone?

[smokekiki]

What shape are your hoses in?The suburban I bought lost antifreeze.The hoses looked allright,but under pressure the one heater hose would seep.

[Chevy Wrench]

There is a company that sells a test kit to see if there is co's present in your coolant. Its just a test strip that you dip into the radiator. I will see if I can find the name of the company. Also, you might want to change to a better plug. I would go with an AC Delco plug. Bosch Platimum's are good for Volkwagen's, not very good for Chevy's. Usually, if there are bubbles present in your rad. that means a leaking head gasket. However, its really hard to diagnose something without seeing it first hand. One more thing is to do a coolant pressure test to see how fast you are losing coolant. Wish I had more for ya, good luck.
You said that the oil wasnt as black as normal. What color is it? Does it look like chocolate milk? If so, then you definately have a blown head gasket.

[COBALT]

Do you smell coolant in the cab while the engine is running? Your heater core may be leaking, and then evaporating the fluid giving you this sweet smell inside the cab especially. If you want to know how it would smell take a tiny bit of coolant and drop it on an exhaust manifold and take a whiff. If you have that smell in the cab then you're burining coolant off your core.

Air bubbles in the radiator indicate combustion gasses in coolant or an air leak somewhere. This could be anything from a leaking head gasket (not blown but leaking enough to allow exhaust gasses get in the coolant) to a leaking intake manifold where the combustion charge is getting into the coolant (but you'd be burning coolant as well).

When you fill your radiator it's always a good idea to leave the top radiator hose disconnected at the thermostat housing while you fill until coolant starts to appear around the thermostat. Then, reconnect. This helps get the air out of the system.

As for the timing the first thing to do is what Chevy Wrench suggested: get TDC figured out, align the distributor, and get that balancer fixed. If you fart around with the distributor without knowing where TDC is on the #1 cylinder you're just wasting time.

Also, get an indicator put on the chain cover. so you can see what the hell you're doing. This may require you to pull the timing chain cover, but since you don't know where TDC is anyway you might as well check. There should be marks on the sprocket and the chain to indicate correct alignment. You may find out that's goofed up too. If it is fix it.

Timing for your motor should be somewhere around 10-14 degrees from TDC counterclockwise from 12 O'clock and not the other way unless you need to retard your timing due to your cam. I have to advance mine, so mine is set to 14 degrees to the left of 0 for the best performance for my puny 350 heads and stock cam. Either way the best way to start setting your timing is with the balancer mark at 0 degrees and work from there.

[bmg]

the oil was just used not completly black. not milky at all..the rad fluid goes down about 1/4 a day. and is bout half full (empty) in bout 6 months. There is a greasy residue at the tube in the rad. just below the filler neck. all hoses are bout 1.5 years old.

COBALT i smell no coolant in the cab or out the exhaust. Yeah i gotta replace the oil pan and gasket maybe i just do a full top end gasket change too. and make sure the timing is correct and put on the right timing marker or change the balancer or go to an electirc water pump. and elec fan set up

[jhow66]

Try a new rad. cap. If old one is weak it will let water out over flow as you drive which is why you cannot see any drips.

[COBALT]

Quarter of a tank a day or a quarter of an inch a day??? That's kinda important.

[bmg]

1/4 inch