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Username Post: 283 popping thru carb        (Topic#213628)
reddon1957 
Contributor
Posts: 155

Loc: st.albans, vermont
Reg: 11-05-08
04-02-09 06:30 PM - Post#1667533    

I have a 62 Impala, 283 with a powerglide. Bought last Oct. and it ran great. I noticed the 2bl Rochester leaking on the intake, so I sent it out for a rebuild. Got it back, idled fine and the choke worked perfect. I spent the winter on floors, braces, rocker panels ect. I started it 3 weeks ago and it idled fine, but when I rev it, it pops (backfires) thru the carb. I installed new plugs,dist cap, points and rotor and set the timing. No Change. I am going to sample my fuel to make sure theres no water or dirt,and double check my firing order. Seems like something may have gone wrong with the carb rebuild? Any body ever run into this before? Is there some adjustment that can be done? Seems like it is too lean. I will call the guy who did the rebuild,but its been so long he may not help me. Any help would sure be appreciated! Thanks

 
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doubleE 
Valued Contributor
Posts: 3797
doubleE
Loc: Eagan MN
Reg: 06-02-03
04-03-09 04:21 AM - Post#1667747    
    In response to reddon1957

I'm going to sound like a broken record but you may want to consider a worn timing chain and gears that could have jumped a tooth or 2. Happened to me a couple of times through the years.
Proud owner of My Blue 62 Impala SS


 
bowtieollie 
ChevyTalk Subject Matter Expert
Posts: 21127
bowtieollie
Loc: See the USA in your Chevr...
Reg: 12-06-99
04-03-09 05:47 AM - Post#1667780    
    In response to reddon1957

Hi reddon,

Before you pull your hair out - put a vacuum gauge on that engine.

If the needle is steady - that is good news

If its wandering - then the problem is bigger than the carburetor.

You may have a sticky lifter/valve (since she sat all winter). Change the oil, add some RISLONE to the new oil and let her run for an hour so the engine readhes operating temperature. The old small block may just fix itself....

Of course, if the fuel is stale- change that and make sure you use STABIL to prevent the fresh fuel from becoming stale fuel in 30 days.
Bowtieollie
Chevytalk.com Moderator


 
danam 
Frequent Contributor
Posts: 1368
danam
Loc: San Francisco, CA
Reg: 11-15-04
04-03-09 07:26 AM - Post#1667812    
    In response to doubleE

I would double check your ignition timing.
[ insert witty comment here ]


 
impala_man101 
Forum Newbie
Posts: 51

Loc: SD
Reg: 11-06-07
04-03-09 08:48 AM - Post#1667879    
    In response to danam

Same thing happened to a friend of mind he left it sitting a while he turned it on it was idling rough and popping. He waited till it got to operating temp gave it a couple of good revs and then it made a loud pop noise from the carb and the nice smooth idle returned.

 
Lynn63 
"5th Year" Gold Supporting Member
Posts: 577
Lynn63
Age: 74
Loc: Vicksburg, MI
Reg: 02-07-09
04-03-09 11:27 AM - Post#1667992    
    In response to reddon1957

Just for grins and giggles, take the rotor off and see if the weights swing out freely. Quite often the old grease gets sticky from setting for long periods.
Lynn63
63 Impala SS
07 Silverado DMax Classic
99 Venture van


Progress so far...


 
reddon1957 
Contributor
Posts: 155

Loc: st.albans, vermont
Reg: 11-05-08
04-03-09 12:33 PM - Post#1668032    
    In response to Lynn63

Thanks for all the help guys. I took a fuel sample-no dirt and no water. I added 5 gallons of fresh gas, checked my firing order- o.k. I pulled all my plugs and cleaned them,regapped, all had a very white tip.I checked my timing again and set it to 4-5 dbtdc. It runs alot smoother and does not pop anywhere as bad as it did before, but still pops on very high rev. only intermittantly. I am thinking it is between timing chain, or carbon build up on an intake valve?? It seems the more I run it, the better it gets. I am going to try a can of seafoam thru the carb next. I will let you know what happens. Sure hope its not the timing chain.

 
Willie's 64SS 
Member
Posts: 135
Willie's 64SS
Loc: Pa.
Reg: 04-10-04
04-03-09 02:57 PM - Post#1668124    
    In response to reddon1957

Mine had a broken push rod.
64 Impala SS 283 4 speed. As my brother says"Rev it up 'til the oil lite comes on,THEN kick in the 4 barrel!!!!"


 
Anytime 
Senior Member
Posts: 1019
Anytime
Loc: Las Vegas
Reg: 05-23-06
04-03-09 03:27 PM - Post#1668138    
    In response to reddon1957

Confirm the timing... I'd try about 10 degrees advanced at idle. Then check your vacuum and weight advance at higher revs and confirm that your advance is kicking in another 20 degrees or so.
Your note looks like you might have retarded it 4 to 5 degrees.
Also, did you try the vacuum gauge?
1964 Impala SS 409 - 400HP 4 speed Convertible
2010 Harley Davidson Electra-Glide








 
60chev 
Contributor
Posts: 105
60chev
Loc: Rotchester, NY
Reg: 01-24-09
04-04-09 05:10 AM - Post#1668479    
    In response to reddon1957

Make sure you have a full 12 volts going to your ignition thru a good resistor to your points. Make sure your points and condensor are good and gapped correctly. Of you have HEI, make sure you have full ignition voltage (12.5-14 volts, no resistance). If all that is good your cam might be going bad. These are a couple things that will cause popping thru the carb. I know, Been there and done that. Good luck...
60chev

57 Bel-Air Wagon 350/2004r


 
carbking 
Senior Member
Posts: 1208
carbking
Loc: Missouri
Reg: 06-14-03
04-04-09 05:44 AM - Post#1668488    
    In response to 60chev

I have heard of carburetors causing a backfire, but in 50 years of working on carbs, never personally experienced this issue. Remember that the carburetor has no spark plug (well, at least for the last 80 years they haven't, once they did).

If you think about it; a backfire through the carburetor occurs when there is fire in a cylinder AND that cylinder's intake valve is not closing.

Now consider the various probable causes:

(A) ignition timing
(B) valve timing
(C) sticky intake valve
(D) burned intake valve
(E) broken intake valve spring
(F) faulty radio suppresent plug wires
(G) other.

This is why most are suggesting timing issues.

You will find it.

Jon.
Good carburetion is fuelish hot air!

The most expensive carburetor you will ever buy.....is the incorrect one you attempt to modify!

If you truly believe "one size fits all", trying walking a mile in your spouse's shoes!


 
Old_Longboarder 
Ultra Senior Member
Posts: 12525
Old_Longboarder
Age: 65
Loc: Long Beach Ca, near Vet's...
Reg: 03-28-02
04-04-09 06:20 AM - Post#1668499    
    In response to carbking

If the "popping" sounds like machine gun fire and gets faster as the RPMs go up, you have an exhaust valve that is not opening all the way or not opening at all. Pull the valve covers and check rocker movement.
Home.., is where dog hair sticks to everything but the dog.





 
reddon1957 
Contributor
Posts: 155

Loc: st.albans, vermont
Reg: 11-05-08
04-05-09 05:42 AM - Post#1669134    
    In response to Old_Longboarder

Just wanted to give an update. I ran half a can of seafoam thru the carb and it sure did not hurt. I let the car run for quite some time and then took it down the road. It now runs alot better only popping now and then. If I rev it up while parked. it will only pop once in a while, nothing steady. It seems the more it runs, the better it gets. I had a couple friends examined my gas sample, and they both feel the gas does not have the strong gas smell it should have.One guy said his ford was doing the same thing and he flushed his tank, sealed it added fresh gas and it ran great.I am going to drain and drop my tank, flush and add fresh gas, and also add rislone if I can find it. Before I do, I am going to try to advance my timing and check vacuum. Does anyone think bad / dirty gas could cause this popping? Or is this just wishful thinking? If nothing else, I will have eliminated the fuel system as possible problem. Thanks for all the help!

 
60chev 
Contributor
Posts: 105
60chev
Loc: Rotchester, NY
Reg: 01-24-09
04-05-09 04:05 PM - Post#1669508    
    In response to reddon1957

Yep, I've had bad gas a few times recently. Fastrac and some others that have a high percentage of ethenol make the older cars run like crap with alot of misfiring, low power and bad gas mileage. I always check now when I go to an unfamiliar station.
60chev

57 Bel-Air Wagon 350/2004r


 
tony1963 
Frequent Contributor
Posts: 1206

Loc: Birmingham AL
Reg: 10-11-08
04-05-09 04:50 PM - Post#1669534    
    In response to 60chev

In my experience, popping through the carburetor has been ignition timing, cross-firing due to bad plug wires and lastly, a worn cam.

Have you removed the valve covers and done a visual that all of the rockers move about the same?
1964 Chevrolet Impala SS 327 Powerglide (SOLD!)
1981 Ford Granada 3.1 L (200 inline 6) (SOLD!)
1985 Chevrolet Suburban C20 454 Turbo 400
1999 Mercedes E300 (SOLD!)
2008 Mercedes E350
2012 Mercedes S550



 
skunk22 
Senior Member
Posts: 483
skunk22
Loc: Ripley, Tn. USA
Reg: 07-05-01
04-06-09 11:48 AM - Post#1670101    
    In response to tony1963

Reddon: Everytime I have had that problem it has been a bad lobe on the cam. Usually the exhaust valve. The exhaust valve does not open and the cylinder has pressure on it when the intake opens thus the gasses are sent back through the intake and carb creating the pop sound. Check your cam lift on all cylinders.
Skunk
Skunk's Den
1964 Impala Conv. LT-1
1966 Corvette 427
1969 Super Bee 440
2005 Mustang
1965 Mustang 2+2
1966 Chevelle
Always looking


 
reddon1957 
Contributor
Posts: 155

Loc: st.albans, vermont
Reg: 11-05-08
04-07-09 12:28 PM - Post#1670918    
    In response to skunk22

Well, after a Qt of reslone in the oil, advanced timing 10 degrees, a can of seafoam thru the carb,freed up the dist weights,it runs about 90% better but still getting the occasional pop at high revs only every now and then.I am going to pump out my old gas tomorrow and replace with fresh. But, while running at idle I heard a kind of hum or vibratin near the back of the engine. After searching for awhile, I placed my hand on the vacuum advance and it was coming from there. Running my finger around it I felt a pretty bad vacuum leak coming from the very bottom. When I plug it the engine idle slows a little. Does anyone think this is my popping problem??? I should not have ANY vacuum leaks right? And maybe because of the leak, my advance is not working properly? I can get a rebuilt dist. with advance from Classic for $59.95 What do you guys think? Sure would appreciate any advice. Thanks

 
60chev 
Contributor
Posts: 105
60chev
Loc: Rotchester, NY
Reg: 01-24-09
04-07-09 12:53 PM - Post#1670938    
    In response to reddon1957

You can just change out the advance unit itself, easy and cheap. I think around $12-15 bucks @ Advance or Autozone. A vacuum leak doesn't help anything when it comes to running properly.
60chev

57 Bel-Air Wagon 350/2004r


 
Trailbum 
"13th Year" Silver Supporting Member
Posts: 2070
Trailbum
Age: 56
Loc: Harpers Ferry, WV
Reg: 11-06-00
04-07-09 12:59 PM - Post#1670943    
    In response to reddon1957

A replacement vacuum advance unit is available through Advance Auto Parts stores.... for under 10 bucks!!!!
(sorry 60Chev... looks like we posted at the same time!!!)
"They say men should get in touch with their feminine side.... Well, if I HAD a feminine side.. believe me, I'd be TOUCHING IT!!!"


Edited by Trailbum on 04-07-09 12:59 PM. Reason for edit: No reason given.

 
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